geology and structural characteristics of the san antonio ... tesis-geology and... · remote...

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Geology and Structural Characteristics

of the San Antonio del Sur Area, Cuba,

Using Data Integration Techniques

Kenya Elvira Nuñez Cambra April, 2000

Thesis Title: Geology and Structural Characteristic of the San Antonio del Sur Area, Cuba, Using Data Integration Techniques

By

Kenya Elvira Núñez Cambra Thesis submitted to the International Institute for Aerospace Survey and Earth Sciences in partial fulfil-ment of the requirements for the degree of Master of Science in Geology. Degree Assessment Board Chairman of the Degree Assessment Board: Prof. Dr. A.G. Fabbri (ITC) External examiner Prof. Dr. S.H. White (University of Utrecht) Director of studies Prof. Dr. F.D. van der Meer (ITC) First Supervisor Dr. A. Prakash (ITC) Second Supervisor Dr. T. Woldai (ITC) Member Dr. C.J. van Westen (ITC)

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ENSCHEDE, THE NETHERLANDS

To my daughters Taisia and Tamara And to my mother.

AKNOWLEDGEMENTS

Acknowledgement

I would like to express my sincere gratitude to people who encouraged and assisted me during my research and to those who contributed to make this study a reality. I am grateful to the Netherlands Fellowship Program for provid-ing me financial support, to study in Holland. I am also thankful to the officials of the Institute of Geology and Pale-ontology, Cuba for allowing me to leave for the study period and for their support all this time. I am very much thankful to the staff and teachers of the ITC Geological Survey Division who helped us to increase our knowledge during the GEO.3 and GEO.2 courses. I address special acknowledgement and I would like to express my sincere appreciation and gratefulness to my first supervisor Dr. Prakash for her guidance, advise and concern extended to me all the time. She always found time out of her schedule, to advise me. Thank you very much. I address special acknowledgement to my second supervisor Dr. Woldai for his comments and required orientation in the thesis. I address special acknowledgements to Mr. Schetselaar for his detailed critiques andcomments and for allowing me to disturb him in any time. My gratitude also for the secretaries, especially to Teresa for their kindness and good treatment in all moment, also to computer cluster managers, and friends from the ITC reproduction department for their assistance. To the officials of the CITMA Ecological Station of Baitiquiri, specially to “Kike” who gave me support during the fieldwork phase in Cuba, as well as direction of the IGP, I am specially thankful to the Subdirectory of Investigation, Dr. Carlos Perez and Luiso, the transport manager. I also especially grateful to Manuel Iturralde-Vinent for his comments, advises and for his special contribution dur-ing the fieldwork and for his valuable and constructive ideas. Special thanks to Dr. Guillermo Millan for his com-ments, advises and for his special contribution during the thin section description and to Mr. J.B de Smeth for thin section preparation. I extend my gratitude to my friends from the CNDIG, Zeida, Hermys and Alfredo who helped me all the time when I needed. I extended my gratitude also to Yoe and Bienvenido. I extend my gratitude also to Enrique for the DTM of the study area. My special thanks to all my friends, my classmate in GEO.3 and GEO.2, Mongon, Amani, Elvis, Tesfair, Samuel, Tamirat and Noor, for sharing all the happiness and sadness moments in ITC with me and corrected my English, thank you very much! Special thanks also to my dear friend Aya. My special thanks to all my friends from Latino-American and Cuban community, who made this time an unforget-table period of my life. Especially to my Enschede sisters Tatiana and Bertha. My gratitude goes to my family and specially to my mother for unconditional support and great strength throughout these long months looking after my two daughters. To my husband Reinaldo for his technical and moral support, his patience and understanding, his help and love. My love goes to my daughters Taisia and Tamara for the patience they had for bearing all those sad moments the separation has brought us, for being the principal reason of my existence and for being the engine of what I achieve.

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ABSTRACT

Abstract

The San Antonio del Sur study area is located in Oriente province, Cuba. The area is characterized by complex geological structures, Eocene to Recent neotectonic active movements and minor NE-SW sinis-tral faulting probably related to transpression along the northern margin of the Caribbean plate. Various investigators have in the past mapped the Geology of the area using conventional approach. How-ever, detailed structural synthesis in the area lacking. The present work was aimed at updating the geological map determining structural characteristic of the area with a view of enriching the understanding of neotectonic movements. Remote sensing offers the most efficient means of fulfilling these objectives. In the study of the San Antonio del Sur, in Oriente province, remote sensing and data integration techniques were used for first time, to demonstrate the po-tential of such data for the mapping of the lithology and structure of the area. This study contains new structural data collected from the field observation and from microstructural study of oriented thin sec-tions. The tectono-stratigraphical column for the area was worked out and the geological map was up-dated. The present work introduces an evolutionary model of the area, which tries to explain the main geo-logic changes in the area and the characteristic of the current relief. In the current study, remotely sensed data enabled the mapping of several lithological and structural ele-ments. Fieldwork allowed the characterization of important lithological boundaries, establish deformation phases, collect and establish time relationship, and evidences of neotectonic movement. Preliminary results obtained after integrating the geological and geophysical data with the remotely sensed and fieldwork data has enabled to map lithological and structural features that previously went unnoticed. It has also allowed for a better synthesis on the tectonic evolution of the San Antonio del Sur area The San Antonio del Sur area has the following evolutional stage: First: Cretaceous period marked by the beginning of the volcanic island arc. At that time the volcano-sedimentary rocks of the Puriales Complex were formed. After Campanian, the Cretaceous volcanic arc became extinct, and these rocks were deformed with first deformation phase (D1). Second: Paleocene to early Middle Eocene. The cretaceous volcanic rocks were thrusted by ophiolite complex. According to the observation, the sense of thrusting can be described coming from the SE to NW. The second deformation phase (D2) occurred.at this time. Third: Middle to Late Eocene. Unit from the Paleogene island arc such as El Cobre Formation was formed. This unit was thrusted over the sediments of the basin in some places. The generation of the thrust movement from SW toward the NE gave rise to the third deformation phase (D3). Fourth: Miocene. Transpressional-transtensional tectonic movement became active along the Oriente fault, The sinistral sense of the movement generated the fourth, predominately brittle, deformation phase (D4).

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TABLE OF CONTENTS

Contents

Abstract ......................................................................................................................................................... ii Contents ....................................................................................................................................................... iii Tables and Figures .........................................................................................................................................v

Figures........................................................................................................................................................v Chapter 1: Introduction ..................................................................................................................................1

1.1. Problem definition..........................................................................................................................1 1.2. Objectives.......................................................................................................................................1 1.3. Scope of present study ...................................................................................................................2 1.4. Structure of the thesis.....................................................................................................................2

Chapter 2: Review of the Geology and Tectonics of Cuba............................................................................5 2.1 Introduction ........................................................................................................................................5 2.2 Geology of Cuba ................................................................................................................................5

2.2.1 The foldbelt ................................................................................................................................6 2.2.2 The Neoautochthon ....................................................................................................................9

2.3 Plate tectonic model of Cuba. ..........................................................................................................10 Chapter 3: The Study area............................................................................................................................21

3.1 Introduction of the Study area..........................................................................................................21 3.1.1 Location....................................................................................................................................21 3.1.2 Climate .....................................................................................................................................22 3.1.3 Geomorphology........................................................................................................................22 3.1.4 Seismic Activity .......................................................................................................................23

3.2 Geology of the Study Area...............................................................................................................23 3.2.1 Stratigraphic features................................................................................................................24 3.2.2 Structural and tectonic features ................................................................................................30

Chapter 4: Data input and Methodology ......................................................................................................33 4.1 Data used..........................................................................................................................................33

4.1.1 Remote Sensing Data ...............................................................................................................33 4.1.2 Ancillary Data ..........................................................................................................................34 4.1.3 Field Data .................................................................................................................................34

4.2 Methodology ....................................................................................................................................35 4.2.1 Preprocessing of Remote Sensing Data....................................................................................36 4.2.2 Processing of Remote Sensing Data.........................................................................................38 4.2.3 Field Data Capture ...................................................................................................................40 4.2.4 Data Integration........................................................................................................................40

Chapter 5: Data Analysis Results and Interpretation ...................................................................................43 5.1 Introduction ......................................................................................................................................43

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GEOLOGY AND STRUCTURAL CHARACTERISTIC OF THE SAN ANTONIO DEL SUR AREA, CUBA, USING DATA INTEGRATION TECHNIQUES

5.2 Geological and structural Section.................................................................................................... 43 5.2.1 Cross section W- E across the Caujeri Valley......................................................................... 44 5.2.2 Cross section NNW - SSE across the Caujeri Valley.............................................................. 47 5.2.3 Cross section in Sierra del Puriales Complex.......................................................................... 50

5.3 Structural Analysis and Neotectonism ............................................................................................ 52 5.3.1 Deformation phases ................................................................................................................. 56 5.3.2 Principal fault system .............................................................................................................. 58

5.4 Tectonic Evolution .......................................................................................................................... 59 Chapter 6: Conclusions and Recommendations .......................................................................................... 65

6.1 Conclusions ..................................................................................................................................... 65 6.1.1 Conclusions on effectiveness of Remote Sensing techniques ................................................. 65 6.1.2 Conclusions on the study area ................................................................................................. 65

6.2 Recommendations ........................................................................................................................... 69 References and Consulted Bibliography ..................................................................................................... 67 Plates .............................................................................................................................................................B Appendices ....................................................................................................................................................H

Apendix 1 Updated Geological Map of the Study Area............................................................................. I Apendix 1a General Legend of Geological Map and Cross Sections. ....................................................... J Apendix 2 Tectonic-stratigraphic map ......................................................................................................K Apendix 3 Main structural data from field observations........................................................................... L Apendix 4 Structural interpretation of the area ........................................................................................M Apendix 5 Locations visited during the fieldwork ....................................................................................N Apendix 6. Cross section on the rivers within the Caujeri Valley ............................................................O Apendix 7. Magnetic data and Radar image with tectonic interpretation ................................................. P

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TABLES AND FIGURES

Tables and Figures

Figures

Figure 2.2.1 Schematic geologic map of Cuba...............................................................................................6 Figure 2.2.2 Tectonostratigraphic sequences of the Cuban foldbelt. ...........................................................7 Figure 2.2.3 Facial map for the Mid Cretaceous marine environments of the Bahamian platform and

slope deposits.. .......................................................................................................................................8 Figure 2.2.4 Main tectonic elements of Neoautochton.. ..............................................................................10 Figure 2.3.1 Major magmatic events related with the evolution of the Caribbean area..............................11 Figure 2.3.2 Model of the original position of Cuban southwester terranes in the early Oxfordian

Mesoamerican realm.. ..........................................................................................................................12 Figure 2.3.3 Evolutionary cross section of the western Caribbean between the Yucatan platform and the

Guaniguanico terrane.. ........................................................................................................................14 Figure 2.3.4 Evolutionary cross sections through Bahamas and Central Cuba. .........................................15 Figure 2.3.5 Main Paleocene-Lower Eocene geological features of the northwestern Caribbean ............18 Figure 3.1.1 Location map of the Study Area...............................................................................................21 Figure 3.1.2 Main geomorphological features of the study Area.................................................................22 Figure 3.1.3 Map with epicenters of earthquake..........................................................................................23 Figure 3.2.1 Geological map as result of geological mapping 1:250 000 scale..........................................23 Figure 3.2.2 Geological map as result of geological mapping 1:100 000 scale.........................................24 Figure 3.2.3 Stratigraphic column of foldbelt. .............................................................................................24 Figure 3.2.4 Geological-schematic Map of metavolcanic cretaceous Purial Complex.. .............................25 Figure 3.2.5 Generalised geological map and cross section of the eastern part of Cuba. ..........................26 Figure 3.2.6 Schematic Cross section for sedimentary sequences along the study area .............................28 Figure 3.2.7 Synthetic Stratigraphic column of Neoautochthon. .................................................................28 Figure 3.2.8 Reconstruction of the possible premiocenic position of Eastern Cuba and Santo Domingo..32 Figure 3.2.9 Plate motion vectors of the Caribbean Plate relative to the North American Plate along the

northern Caribbean Plate boundary. ...................................................................................................32 Figure 4.2.1 Flowchart of Applied Methodology ........................................................................................35 Figure 4.2.2 Selective contrast image enhancement ...................................................................................37 Figure 4.2.3 Images Processing Techniques . .............................................................................................38 Figure 4.2.4. Methodology for integration Spot and Landsat TM ...............................................................39 Figure 4.2.5 Methodology for integration Radar and Aeromagnetic data ..................................................41 Figure 5.2.1 Cross section 1-1 W-E across the Caujeri Valley....................................................................45 Figure 5.2.2 Cross section 2 –2 NNW - SSE across the Caujeri Valley......................................................47 Figure 5.2.3 Cross section 3 – 3 SW – NE in the Puriales Complex...........................................................50

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Figure 5.2.4 Type 1 of four principal types of three-dimentional fold forms arising by the superposition of shear folds on pre-existing fold forms ................................................................................................. 51

Figure 5.3.1 Structural domains for Study Area.......................................................................................... 53 Figure 5.3.2 Clasification of mantled porphyroclasts. Sinistral sense of shear .......................................... 54 Figure 5.3.3 Rose diagrams of main fractures and stereo-contour diagram of bedding for differents

structural domain. ............................................................................................................................... 55 Figure 5.3.4 Contour Stereoplot for structural features on the Puriales Complex ..................................... 57 Figure 5.3.5 Main lineament extracted from image interpretation. ............................................................ 58 Figure 5.3.6 Regional strain ellipse associated with a strike-slip fault system. .......................................... 58 Figure 5.3.7 Rose diagram of the main fracture system for the study area................................................. 58 Figure 5.4.1 Evolution Model for the study area......................................................................................... 60 Figure 5.4.2 Tectonic-stratigraphic column for the study area subdivided by different structural domain 61 Figure 5.4.3 Tectonic stratigraphic map of the area ................................................................................... 62 Figure 5.4.4 Blockdiagram of structural interpretation …………………………………………………..63

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CHAPTER 1. INTRODUCTION

Chapter 1: Introduction

The study area is located in Oriente province in the eastern part of Cuba, which is geologically identified as Neotectonic East Province. This province is characterized by a complex geological structure, where Eocene to Recent vertical oscillatory movements were dominant with minor NE-SW sinistral faulting probably related to transpression along the northern margin of the Caribbean plate. No magmatic activity is recorded. New basins evolved above the deformed belt with clastic and carbonate deposition. The present study intends to clarify the geological and structural characteristic of the San Antonio del Sur area and to deduce its tectonic history.

1.1. Problem definition

Introduction to the problem: The study area is placed at the northerner border of the plate boundary be-tween the North American and Caribbean plates, which is highly affected by transpressional sinistral movement of the Oriente fault. The structural studies in the area are limited, and the influence that particu-lar geotectonic situation has on the area is still unknown. In the last few years several studies involving the geology in the eastern part of Cuba were carried out. Previous works were mostly based on field observa-tion and aerial photo interpretation. Geology and tectonic structures of the area, however, have been stud-ied using a conventional mapping approach with full consideration to using remotely sensed data and data integration using GIS. The area being geologically complex covered by vegetation, and for the most part inaccessible, implies the usage of remotely sensed data to be a valuable asset in the mapping of the geol-ogy and structural features of the area. The problem: Detailed structural synthesis is lacking, there is an evident insufficiency of geological structural knowledge of the area.

1.2. Objectives

The main objective of this research is to study the geology of the San Antonio del Sur area, with emphasis on structural characteristics in order to evaluate the tectonic evolution of the sector. Using field observations, remote sensing and data integration techniques the following objectives will be reached: • Update geological map of the area • Determine the geological structure of San Antonio del Sur sector

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• Develop an evolution model of the San Antonio del Sur sector.

1.3. Scope of present study

In the study of the San Antonio del Sur, in Oriente province Remote Sensing and Data Integration Tech-nics were used for first time, to demonstrate the potential of such data for the mapping of the lithology and structure of the area. This study contains new structural data collected from the field observation and from microstructural study of oriented thin sections. The tectono-stratigraphical column for the area was worked out and the geological map was updated. The present work introduces an evolutionary model of the area which tries to explain the main geologic changes in the area and the characteristic of the current relief.

1.4. Structure of the thesis

The present work includes six chapters, reflecting the methodology and the approache adopted to address the outstanding questions regarding the structure of the area. Chapter 1 includes an introduction to the problem defining the area main objectives of the research. The importance of Remote sensing and GIS techniques for increasing the geological and structural knowledge of the area is also outlined. Chapter 2 gives a literature review on the general geology of Cuba and the most updated plate tectonic model applicable for Cuba, with especial emphasis on the eastern region of the country. Chapter 3 presents a general introduction to the geology and tectonics of the study area and an updated and comprehensive review of the work done by several researchers in this area. In describing the various geological formations that occur in the study area, some information concerning the thickness and age of the formations are taken from earlier works. Most of the lithological and structural descriptions are based on the authors own observation made during the fieldwork carried out in October to November of 1999. Chapter 4 contains the data input and methodology carried out to execute the research. In this chapter the list of data available, the way that was input, processed and integrated for analysis is described. Also, the use of different remote sensing data such as, Landsat TM, SPOT, airborne geophysical and field data, and the way in which these datasets can be integrated in order to get better product for visualisation and final interpretation are analyzed.

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CHAPTER 1. INTRODUCTION

Chapter 5 contains the analysis and interpretation of the data sets used in this research. It includes a de-tailed geological and structural description of characteristic cross sections through the area; Structural analysis based on the field data collected, observation and evidence directed towards a complex tectonic setting of the area and Neotectonic activity. The evolution model for the area (developed based on the analysis of results) is also done. Chapter 6 contains conclusions and some recommendations for future research. At the end of the thesis appendices and photograph of the filed observations are included. Several final maps and photograph, which appear, listed and mentioned in the text, as it was necessary, used Appendix and Plate with a number respectively.


CHAPTER 2. REVIEW OF THE GEOLOGY AND TECTONICS OF CUBA

Chapter 2: Review of the Geology and Tectonics of Cuba

2.1 Introduction

This chapter presents a general introduction to the geology and tectonic of Cuba and an updated and com-prehensive review of the work done by several researchers in this area.

2.2 Geology of Cuba

Considerable geological research has been carried out in Cuba during the last years. Several papers and books have been published on the subject. Geological cartography includes a 1: 250 000 scale map of the island prepared by the Academies of Sciences of Cuba, Hungary, Poland, Bulgaria and the former USSR (Kantshev et al. 1976, Iturralde-Vinent, Thounev, Cabrera et al. 1981, Somin and Millan 1981, Nagy et al. 1983, Albear et al. 1985, Pszczolkoswski et al. 1987, Pucharovsky 1988). Besides this, 1:50 000 and 1:100 000 scale geological maps of approximately 70% of the land areas exist which was prepared by ge-ologists from Cuba, Germany, Czechoslovakia, Hungary and the former USSR. Geological studies were accompanied by geochemical, gravity, magnetic and seismic surveys. Many publications deal with the interpretation of the origin and evolution of Cuba, and include tectonics maps at various scales (Shein et al. 1985, Pusharovsky et al. 1989). Reports have also been published on the geology and tectonics of the Caribbean realm and these provide a framework in which to place the Cuban geology (Dengo and Case 1990). Recently a book about Cuban ophiolites and volcanic arcs was published by Iturralde-Vinent (1996). This book not only provides an overview of the geology of Cuba, but also presents a classification of the Cu-ban’s tectonic units. The geological composition and structure of the Cuban archipelago is the most complex in the northwest-ern Caribbean. On Fig. 2.2.1, the two main structural levels recognized by Iturralde-Vinent, (1994) namely, the neoautochthon level and the foldbelt are shown.



Figure 2.2.1 Schematic geologic map of Cuba, showing the two major units, representing the foldbelt and a neoau-thochthon unit. The outcrops of the foldbelt are distinguished by various patterns, while the neoautochthonous part is represented without pattern. (AfterIturralde-Vinent ,1996).

2.2.1 The foldbelt

The foldbelt can be subdivided into: Continental units, comprising Mesozoic Bahamian Platform and slope deposits, which are overlain by a Paleocene-late Eocene foreland basin; and the Cuban SW terranes (Guaniguanico, Pinos and Escambray), which were probably originally attached to the Yucatan Platform. Oceanic units, namely: the norther ophiolite belt; the Cretaceous (? Aptiano-Campanian) volcanic arc, which is overlain by a series of Latest Cretaceous- Late Eocene piggy back basins; and the paleocene-Middle Eocene volcanic arc, which is overlain by a late Middle – latest Eocene piggy back basin. (Fig. 2.2.2).

2.2.1.1 Continental elements

The Bahamas platform The Bahamas platform belongs to the Florida Strait Block of Pindell (1985), and outcrops along the north-ern half of Cuba (Fig. 2.2.3). Within the platform, shallow-water carbonates and evaporites are dominant, but deep-water carbonates and cherts (channel facies) are also present. The carbonate platform contains Jurassic to Latest Eocene clastics, evaporites and limestones. Southward, the section changes into isochro-nous continental slope and basinal deposits composed of limestone, shales, fine-grained clastic and chert (Khudoley 1967; Meyerhoff and Hatten 1968,1974; Pardo 1975. Several examples of these lithologies can be found in Cuba (Iturralde-Vinent, 1996).



Figure 2.2.2 Tectonostratigraphic sequences of the Cuban foldbelt. (After Iturralde-Vinent,1996). SW Cuban Terranes

Composite terranes crop out in three places in southwestern Cuba: Guaniguanico, Pinos (Isle of Youth) and Escambray. The lithostratigraphy of these terranes is very complicated, with different types of sec-tions mixed together, strongly deformed and metamorphosed. The most widespread rocks include the Mesozoic continental margin deposits which, are present in all three terranes with many similar character-istics. Ophiolite rocks (serpentinites, gabbroids, diabases and basalts) are present on thrust planes in Guiguanico and Escambray, and in the later, showing high-P metamorphism.

2.1.1.2 Oceanic elements

The Northern ophiolitic melange.

An allochthonous ophiolitic melange occurs in the northern half of the country and has been thrusted north-and northeastward into the foreland basins (i.e. the Guaniguanico and Bahamas Platform. Figs. 2.2.1and 2.2.2). The ophiolites are composed of two major elements. The melanocratic basement com-posed of ultramafic and mafic igneous rocks of latest Triassic (?) to Lower Cretaceous age, and the oce-anic complexes composed of Hauterivian-Turonian tholeiites interbedded with radiolarites, limestones and shales (Iturralde-Vinent, 1989). This volcano-sedimentary section has been identified as backarc-marginal sea deposits because they are isochronous with the volcanic arc section and were laid down in a different basin (Iturralde-Vinent, 1999a). Large metaflyschoid blocks are present within the ophiolite melange (Somin and Millan, 1981) and may also be interpreted as backarc-marginal sea deposits.



The northern ophiolite melange has a complex tectonic position, which varies, in different parts of the country. In eastern Cuba (see Fig. 2.2.1), the ophiolite thrust-sheet is up to 1km thick and rests subhori-zontally on Cretaceous backarc volcanoclastic (Knipper and Cabrera, 1974; Fonseca et al., 1984; Bush and Sherbacova, 1986; Iturralde-Vinent, 1989,1994; Puscharovsky, 1988; Puscharovscky et al., 1989; Ando et al., 1989). The Northern Ophiolites, in general, was interpreted as a deformed Mesozoic marginal sea –back arc basin (Iturralde-Vinent, 1996).

Figure 2.2.3 Facial map for the Mid Cretaceous marine environments of the Bahamian platform and slope de-posits. (After Iturralde-Vinent ,1996). The Cretaceous island-arc Cretaceous island-arc rocks are widely present in Cuba (Fig 2.2.1). The basement of the arc is a pre-Aptian oceanic crust that can be recognised in parts of Central and Eastern Cuba, and it is represented by amphibolitic ophiolites of the Mabujina and Guira de Jauco complexes (Somin and Millan, 1981; Itur-ralde-Vinent, 1989). These ophiolites may theoretically be as old as the early proto-Caribbean crust (i.e. Jurassic). Oxfordian and older continental margin basalts have been reported in the circum-Caribbean area (Bartok et al., 1985; Iturralde-Vinent, 1988c). Part of the arc’s oceanic basement may also be metadia-bases (spilitic rocks) found in deep, exploratory wells (Vegas and Mercedes, Fig. 2.2.1) South of La Ha-bana and Matanzas provinces (Somin and Millan, 1981) unconformably underlying the volcanic arc sec-tion and the ophiolites in the Mabujina amphibolites.



The island-arc (Fig. 2.2.2) is composed of extrusive and volcanoclastics of Aptian (?) to late-Campanian age with typical tholeitic to calc-alkaline and alkaline composition (Meyerhoff and Hatten, 1968; Khu-doley and Meyerhoff, 1971; Iturralde-Vinent, 1976-77; Pardo, 1975; Cobiella et al., 1977; Nagy et al., 1983; Albear et al., 1985; Diaz de Villalvilla and Dilla, 1985; Talavera et al., 1985; Tchounev et al., 1986; Pszczolkowski et al., 1987; Kozak et al., 1988; Iturralde-Vinent, Wolf and Thieke, 1989). The Paleogene Island Arc Paleocene to early Middle Eocene island-arc suites are well known in eastern Cuba, but never found else-where in the island (Lewis and Straczek, 1955; Iturralde-Vinent, 1976-77; 1981; 1990; Cobiella, 1988; Cobiella et al., 1977; Bresznyanszky e Iturralde-Vinent, 1978; Nagy et al., 1983). The axial portion of the arc, composed of calc-alkaline extrusive and pyroclastics rocks intruded by granodiorites and granite plutons, is present along the Sierra Maestra (Fig 2.2.1). Northwards, only backarc pyroclastics and sediments are present while to the west, Central and Western Cuba, Paleogene volcanism is represented by thin, tuffaceous intercalations within the sedimentary sections of the piggy-back basins. Volcanic activity diminished and became extinct about early Middle Eocene. Major intru-sions took place by late Middle Eocene. Middle to Late Eocene carbonates and clastics were deposited conformably in post-arc basins on to the island arc rocks. The Cretaceous to Oligocene rocks in Eastern Cuba and Northwestern Caribbean Island of Hispaniola are so remarkably similar that there is no doubt that they were part of the same foldbelt. These facts also suggests that Hispaniolan terranes, as they are evident today (Mann et al. 1992) were de-tached from Eastern Cuba after the Oligocene. Lower Miocene deposits, with large clinoforms, south of Eastern Cuban, also corroborate the timing of the disruption event that was coeval with the opening of the Cayman trench.

2.2.2 The Neoautochthon

The geology of the uppermost Eocene-Recent has been described in some detail by Iturralde-Vinent (1978, 1988b). During this time, oscillatory vertical movements were dominant with minor NE-SW sinis-tral faulting probably related to transpression along the northern margin of the Caribbean plate. No mag-matic activity is recorded. New basins evolved above the deformed belt with clastic and carbonate deposi-tion. Three main stages in the evolution of these basins can be recognized, each one representing a complete cycle of transgression and regression; latest Eocene to Oligocene, Lower Miocene to late Miocene and Pliocene to Recent. However, throughout this time, uplift dominated the overall tectonic evolution (Itur-ralde-Vinent, 1996).



Neoautochton evolution began after the activation of the Oriente-Swan Fault Zone, when compressive stresses in the Caribbean Plate shifted to the East, and trusting collisional tectonic environments ceased in Cuba. According to Iturralde-Vinent (1991), the Oriente fault evolved in two stages: first by Late Eocene-Oligocene sinistral strike-slip displacement with deformation along the trend of the fractures; and sec-ondly, during the Miocene-Recent, with sinistral strike-slip and extensional displacements (pull-apart ba-sin formation). As a consequence, the pre-Miocene rocks on the southern flank of the Sierra Maestra are strongly de-formed while the Miocene and younger deposits are horizontal or only slightly tilted, and have been up-lifted more than 200 meters above sea-level (Iturralde-Vinent, 1996).

Figure 2.2.4 Main tectonic elements of Neoautochton. Minor NE-SW sinistral faulting probably related to tran-spression along the northern margin of the Caribbean plate are dominant (AfterIturralde-Vinen , 1996).

North and NE of the Sierra Maestra the latest Eocene-Recent deposits in Cuba are slightly deformed with synsedimentary deformations related to normal faulting and minor strike-slip faults. Roughly parallel with the Oriente fault are the Nipe-Guacanayabo, Camaguey, La Trocha, and Pinar faults, with less than 50 km

of sinistral wrench displacement and minor deformations along very narrow strips. (Fig 2.2.4; Iturralde-Vinent, 1978;1988b;1996).

2.3 Plate tectonic model of Cuba.

Many plate tectonic models have been pro-posed to explain the origin and evolution of the Caribbean Realm, but most of them con-tradict major aspects of Cuban geology (Itur-



ralde-Vinent, 1996). There are three main points of conflict: (1) the early reconstruction of Pangea; (2) the orientation of the Cretaceous island arc; and (3) the orientation of the Paleogene island arc.

Figure 2.3.1 Major magmatic events related with the evolution of the Caribbean area. (After Iturralde-Vinent, 1996). The author’s current ideas on the plate tectonic evolution of Cuba are presented in Iturralde-Vinent (1996), as paleogeographic maps and two sets of paleotectonic profiles; one oriented NE-SW on the southern edge of Bahamas and the other NW-SE at the edge of the Yucatan Block. These profiles integrate the sedimentary, magmatic and tectonic events that have been described previously, in order to answer the above three questions. As well, the evolution of the magmatic activity in Cuba and its surroundings areas has to be taken into consideration (Fig 2.3.1). The evolution on the Western Caribbean area (including Cuba) can be traced in several stages, starting by those proposed by Sawyer et al. (1991).

Late Triassic-Early Jurassic According to Sawyer et al. (1991), this is “the early phase of rifting” in the Gulf of Mexico, but the same is true for the whole pre-Caribbean area.. This was the initial phase in the break-up of Pangea (Pindell, 1985; Ross and Scotese, 1988) (Iturralde-Vinent, 1988c; Figs. 2.2.2 and 2.3.1). In the early reconstruction of the Caribbean (Iturralde-Vinent, 1996), the southernmost Bahamian margin (Central Cuba) and northern South America (Guyana Shield) were very close (Fig 2.3.2). One can con-clude from this interpretation that the contact between Grenville and Pan African basements was located near the suture between Lawrasia and Gondwana along the northwestern Caribbean



Figure 2.3.2 Model of the original position of Cuban southwester terranes in the early Oxfordian Meso-american realm. According to the early reconstruction of the Caribbean, the south-ernmost Bahamian margin (Cen-tral Cuba) and northern South America (Guyana Shield) were very close (After Iturralde-Vinent, 1996).

Middle Jurassic In the Gulf of Mexico “the main phase of crust attenuation” took place and “thick salt was deposited throughout the broad central area” (Sawyer et al., 1991). In the SW Cuban Terranes and the Strait of Flor-ida block clastic deposition and some continental magmatism took place (Fig. 2.2.2 and 2.3.1). These rocks are associated with ammonites that suggest a Tethyan-Pacific Ocean communication (Bartok et al., 1985). This implies that within the mesoamerican area earliest break-up took place between the Yu-catan Block and South America.

Late Jurassic-Earliest Cretaceous

Late Jurassic is characterized by the emplacement of oceanic crust after sea-floor spreading began along a generally east-west-striking weakness in the thinning continental crust that was accompanied by a general transgression into the Gulf of Mexico basin area as the basin began to cool and subside. (Sawyer et al., 1991). An important Oxfordian continental margin basalt event is recorded in the Guaniguanico Terrane (Figs. 2.3.2 and 2.3.1). In the early Caribbean sea (Guaniguanico and Escambray) a major Oxfordian marine transgression took place and spread into the Gulf of Mexico. Deposits associated with this transgression



in Guaniguanico contain a very rich Caribbean Jurassic biota (Ammonites, fish, pterosauria, plesiosauria, crocodiles, pelecypods, etc), that has some relationships with the Eastern Pacific and European faunas. This suggests that there was faunal exchange between the Pacific and the Tethys. (Bartok et al., 1985) Many Caribbean plate tectonic models interpret this stage with various success but fail to take into account the Pinos and Escambray terranes, just ignoring its existence, or consider them as unrelated units (Pindell, 1985; Ross and Scotese, 1988; Pindell and Barrett` 1990; etc.). The evolutionary profiles in Fig. 2.3.3 were constructed by reorganizing the belts of the Guaniguanico Terrane approximately parallel with the Yucatan margin (Iturralde-Vinent 1996). This area evolved from pre-Oxfordian intra-continental rifting to a Kimmeridgian-Early Cretaceous passive-margin. Later, during the opening of the western Yucatan oceanic basin (Rosencrantz, 1990), these terranes became detached from the Yucatan Platform and were incorporated into the Cuban Foldbelt. The southern margin of the Bahamas Platform (Strait of Florida Block) was strongly affected by sinistral transform movements, while the eastern margin of the Yucatan Block and the Gulf of Mexico basin evolved parallel to the ocean ridges. The development of the late Oxfordian-early Tithonian carbonate platform and its basinal equivalents in Guaniguanico and Escambray (Yucatan Block borderland) indicate that rifting continued during the whole Late Jurassic. In the Gulf of Mexico and the Caribbean margin areas, subsidence has taken place since Tithonian, a byproduct of cooling of the oceanic crust (Iturralde-Vinent, 1996).

Cretaceous

Since Early Cretaceous time the Gulf of Mexico was mostly a stable area with general subsidence and lo-cal uplift (Sawyer et al., 1991). In the proto-Caribbean realm, however, the geodynamic environment was drastically modified, probably associated with the opening of the South Atlantic Ocean. As a consequence, extensional stress changed to compressional (plate convergence), continental margin magmatism van-ished, and island-arc evolution was initiated (Figs.2.3.1). The early oceanic crust of the Caribbean began to be subducted, while backarc spreading occurred in the NW Caribbean. Basalt volcanism took place under a backarc (suprasubduction) environment from the Hauterivian through Turonian and is found within the ophiolites in northern Cuba (Figs. 2.2.2 and 2.3.1) Concerning this stage in the evolution of the western Caribbean the problem of the original orientation of the Cretaceous arc and its subduction zone needs to be considered. However, several lines of evidence point toward a northward-dipping subduction zone located south of the present-day volcano-plutonic out-crops (Iturralde-Vinent, 1981; 1988a; b; c; 1996). Rosencrantz (1990) has interpreted a northward-dipping reflection as a fault plane on a seismic line lo-cated between southcentral Cuba and the Yucatan basin (Fig. 2.2.1, SE of Camaguey). The fault now is inactive and buried by Tertiary sediments. This fault can be interpreted as the suture of the Cretaceous subduction zone. Therefore, the outcrop of the suspected subduction plane can be traced south of Cuba, an



interpretation that is in agreement with the distribution of the arc-related volcanics and plutonics rocks in Cuba (Fig. 2.2.1) (Iturralde-Vinent, 1996).

Figure 2.3.3 Evolutionary cross section of the western Caribbean between the Yucatan platform and

the Guaniguanico terrane. Leyend as in Fig. 2.3.4. Location in Fig. 2.3.2. (After Iturralde-Vinen, 1996).

Within the Bahamian continental rise deposits (Placetas belt), intercalations of volcanic ash and pyroclas-tic debris within the Albian-Cenomanian-Turonian section have been reported. This suggests that the arc and Bahamas were in relatively close proximity at that time. Also, Maastrichtian and Paleocene to Eocene deposits in the Placetas and Camajuani Belts contain large blocks of Cretaceous volcanic and intrusive rocks, suggesting that the volcanic arc was never far away from its present position. Renne et al. (1991), based on paleomagnetic research, suggested that the Cretaceous volcanic arc was located between 200 and 1,600 km south of its present location during the Albian-Cenomanian.



In several plate tectonic models the northern Cuban ophiolite melange is considered to be part of the Proto-Caribbean crust while the arc is related to Pacific crust (Pindell, 1985; Ross and Scotese, 1988; Pindell and Barret, 1990; etc). This framework does not explain the fact that ophiolite gabbroids in Camaguey Province (Fig. 2.2.1) have the highest alkali concentration of any such rocks on the island and that the same primary anomaly is present in Cretaceous volcanic and intrusive rocks in this area (Fonseca et al., 1984). These geochemical anomalies in crustal and supracrustal rocks cannot be coincidental. The existence of eclogites and blueschists has been the supporting evidence for interpreting the northern ophiolite melange as a subduction complex (Somin and Millan, 1981; Ando et al., 1989). High-P meta-morphic rocks are not abundant in the northern ophiolite melange (<< 3% of the volume) and are gener-ally found along linear belts of cataclastic serpentinites (which are a few kilometers wide and tens of kms long) associated with high-T and non-metamorphic rocks (Somin and Millan, 1981; Kosak et al., 1988). The high-P metamorphic inclusions within the ophiolite melange may also be associated with strike-slip combined with dip-slip movements. This framework can be described as non-magmatic underthrusting at the Bahamas-Proto Caribbean crust contact, along the same trend of the Mesozoic transform boundary (Fig. 2.3.2). Rigassi-Studer (1961) and Iturralde-Vinent (1981) have described strike-slip features along this suture in central Cuba, while thrusting is well known in the same area (Meyerhoff and Hatten,1968). This kind of tectonic framework has been described for many plate boundaries, including the Puerto Rico trench (Dengo and Case, 1990). K-Ar ages derived from high-P rocks of the northern ophiolite melange [58-12 8 Ma (n=31)] and mag-matic rocks of the Cretaceous volcanic arc [49.5-100.1 Ma (n=79}]. Indicate that older thermal (tectonic) events are recorded within the ophiolites (Iturralde-Vinent et al., 1992). K-Ar ages in the ophiolites sug-gest a minimun age of Lower Cretaceous for the first High-P metamorphic event in the ophiolites (Somin and Millan, 1981); Millan and Somin, 1985b). This event may reflect the activity of the fault located south of the Bahamian platform. The just mentioned Early Cretaceous or older high-P metamorphic event recorded in the ophiolites, if it is interpreted as a subduction-related event, is problematic for the Plate tectonic models that require a pre-Albian north diping subduction zone (Ross and Scotese, 1988; Pindell and Barrett, 1990). This subduction suture is placed south of the arc in these models, and the ophiolites are present in the northern flank of the arc.

Figure 2.3.4 Evolutionary cross sections through Bahamas and Central Cuba, characterizing the western Caribbean history. Location on Fig. 2.3.2. (Taken from Iturralde-Vinent, 1996).



The K-Ar age pattern is in agreement with the tectonic model proposed here. According to this model (Figs 2.3.3 and 2.3.4), Pinos and Escambray terranes were underthrusted below the arc since the end of the Cretaceous, while the northernn ophiolites had a long-lasting deformation history related with the Carib-bean-Bahamas (plate) boundary.

Figure 2. 3.4 (cont.) Evolutionary cross sections through Bahamas and Central Cuba, characterizing the west-ern Caribbean history. Location on Fig. 2.3.2. (Taken from Iturralde-Vinent, 1996). If a north-dipping subduction zone for the Cretaceous volcanic arc proves to be true, and the arc origi-nated within the Caribbean, many Caribbean plate tectonic models must be reformulated (Pindell, 1985; Shein et al., 1985; Ross and Scotese, 1988; Pszczolkowski; 1987; Pindell and Barrett, 1990; and many others) (Iturralde-Vinent, 1996).

The evolution of the Cretaceous volcanic arc in the Cuban area reflects two important events; one during Albian and the other during Coniacian-Santonian, as discussed above (Fig. 2.2.2). Such events are not only related to tectonic processes within the Caribbean, but they have global conterparts (Schwan, 1980). This fact suggests that these two events can not be explained just as local phenomena related to the geo-logical history of the arc. More probably they are local reactions to global tectonic transformations. The Cretaceous arc split into two about Albian time and one part became inactive as a remnant arc (Figs. 2.3.3 and 2.3.4). Thereafter, the active arc migrated southward and extensional stresses were developed between the arc and the Bahamas Platform. As a consequence, the backarc basin became enlarged and the Bahamas Platform was fractured. A number of deep water-channels divided the platform into separate shallow-water areas (Fig. 2.2.2). It is well known that the long-lasting Cretaceous positive magnetic event ended about Santonian as a con-sequence of global tectonic events (Schawn, 1980). Coincidentally, the Caribbean tectonic regime suffered a major change. After Campanian the Cretaceous volcanic arc became extinct, and deformational proc-esses started along the NW Caribbean margin (the North Caribbean Orogeny; Pszczolkowski and Flores, 1986). As a consequence, foreland basins evolved along the southern Bahamian and NE Yucatan margins and “piggyback” basins developed above the aborted Cretaceous volcanic arc (Figs. 2.3.3 and 2.3.4). South-



ward underthrusting of the Bahamian slope deposits and part of the ophiolites took place later during the evolution of the foreland basins (latest Cretaceous-Late Eocene). Simultaneously, formation of oceanic crust probably began within the western Yucatan basin, a process that is generally recognized for Paleo-cene Midle to Late Eocene time (Rosencrantz, 1990). In some areas of the foldbelt outcrops low degree high-P complexes (Cangre, in Guaniguanico; metavul-canics of Purial, metaophiolites of Guira de Jauco and metasedimentary rocks of Asuncion, in Eastern Cuba). These rocks were metamorphosed within the Maastrichtian-Paleocene interval (Somin and Millan, 1981; Millan and Somin, 1985a, b) but can not be explained by a magmatic-producer subduction because they can not be related with contemporaneous arc rocks. In Eastern Cuba the Paleocene-Eocene volcanics stratigraphically overlie these metamorphic rocks (Iturralde-Vinent, 1996). At the present time these metamorphic rocks are located along strike-slip and thrust faults (Cangre), or are piled as superimpossed thrust sheets (Eastern Cuba). Iturralde-Vinent believe, on the base of geological observations, that this metamorphism is related with overpressure due to thrusting of heavy tectonic sheets as the ophiolites (Iturralde-Vinent, 1996).

Latest Cretaceous-Late Eocene

Starting in the latest Cretaceous in some places and since Paleocene in eastern Cuba, a new volcanic arc (or set of arcs) evolved facing the Caribbean Sea (Fig. 2.3.1). In most Caribbean plate tectonic models, Paleocene-early Middle Eocene volcanic activity is related to a subduction zone dipping S, located N of the Greater Antilles including the Cuban area (Pindell, 1985; Ross and Scotese, 1988; Pindell y Barrett, 1991; etc.). But again this contradicts the known geometry of the volcanic-plutonic suite, and is not sup-ported by the geology of Cuba. A Paleogene subduction zone has not been recognized on – or offshore in Cuba (see geologic and tectonic maps: Pushcharovsky, 1988; Puscharovsky et al., 1989).



Figure 2.3.5 Main Paleocene-Lower Eocene geological features of the northwestern Caribbean. In Cuba, the Paleocene to early Middle Eocene volcanic arc rocks overlaps only partially the Cretaceous arc suites as the younger arc is located S and SE of the former (AfterIturralde-Vinent, 1996).

On Cuba, all observations point to a Paleocene to early Middle Eocene subduction zone located S of the arc and dipping N or NW (Cobiella, 1988; Iturralde-Vinent, 1988c; 1990). This subduction zone was de-veloped some distance away from Cuba but is probably represented in Hispaniola because these terranes were originally located south of Eastern Cuba during early Tertiary (Bresznyansky and Iturralde-Vinent, 1978; Cobiella, 1988; Ross and Scotese, 1988; Pindell and Barrett, 1990). Conglomerates and sandstone become coarser southward in Eastern Cuba, which suggests the presence of a provenance area south of the Sierra Maestra. This source was most probably Caribbean island of Hispaniola, as has been pointed out by many authors (Bresznyanszky e Iturralde-Vinent, 1978; Cobiella, 1988; Iturralde-Vinent, 1988b, 1996; etc). The extinct subduction suture for the Paleocene-Eocene arc is probably located in the Peralta-Ocoa Belt of SW Hispaniolal, which strongly resembles an accretionary prism (Unruh et al., 1991), as several features suggest (Fig. 2.3.5; Huebeck et al., 1991). Furthermore, deformation and metamorphism of latest Cretaceous to Late Eocene rocks in the belt is time-equivalent with magmatic activity in SE Cuba. Post Eocene sedimentation and deformation in the Peralta-Ocoa Belt-Muertos Trough was probably related to sinistral strike-slip movements associated with the



Oriente fault system (Mann et al., 1992) and deformations along the Sierra Maestra of Cuba (Iturralde-Vinent, 1991). In Cuba, the Paleocene to early Middle Eocene volcanic arc rocks overlaps only partially the Cretaceous arc suites as the younger arc is located S and SE of the former (see Figs. 2.2.1 and 2.3.5). Therefore, the Paleogene subduction zone was probably located SE of the previous (Cretaceous) zone. Eastward, in the Hispaniola-Virgin Islands area, the early Tertiary subduction zone probably followed the same trend and position of the Cretaceous and Paleogene arcs complexes are generally superimposed in these territories (Khudoley and Meyerhoff, 1971; Dengo and Case, 1990). There may be a number of local explanations for the “jump to the SE” of the subduction zone in the West-ern Caribbean at the end of the Cretaceous, but it may be a byproduct of global tectonic events that started in the Santonian (Schwan, 1980).

Latest Eocene to Recent

A final important geodynamic change in the western Caribbean, as elsewhere (Schwan, 1980), took place in about the middle-late Eocene, and was probably related to activity of the Swan–Oriente strike-slip fault which has evolved since the Miocene into a rift-transform system (Itrurralde-Vinent, 1991). As a conse-quence, plate convergence shifted towards the Eastern Caribbean along the Lesser Antilles arc. Within the western Caribbean, in the so-called Cuban microplate, transpressional-transtensional tectonic environments became active and oceanic crust was produced at the Cayman Ride (Figs. 2.2.4). Some strike-slip faulting and minor deformations were associated with vertical oscillatory movements along the Cuban neoautochthon (Iturralde-Vinent, 1996).


CHAPTER 3. THE STUDY AREA


Chapter 3: The Study area

This chapter presents a general introduction to the geology and tectonic of the study area and an updated and comprehensive review of the work done by several researchers in this area. In describing the various geological formations of the study area some information, such as the thickness and age of the formation were refered from earlier works. Most of the lithological and structural descriptions however, are based on the authors field observation carried out in October to November of 1999. The structural setting of the study area as concluded by earlier workers is presented along with the author’s own view on this aspect.

3.1 Introduction of the Study area

3.1.1 Location

The study area is about 20x30 km, and lies in the north of San Antonio del Sur village, in Oriente prov-ince, in the eastern part of Cuba (Fig. 3.1.1). The geographic coordinates is given by Latitude: 19°59’26. 4’’ N; Longitude: 74°55’20. 3’’W and Latitude: 20°15’33. 9’’ N; Longitude: 74°43’39. 0’’W. The area is about 55 km East of Guantanamo City. The accessibility of the area is very difficult. There is one principal road running East-West parallel to the Southern coast, from Baitiquiri village to Imias Village. Another road runs from South to North, through the central valley of Caujeri, from San Antonio Village to Puriales de Caujeri Village.

Figure 3.1.1 Location map of the Study Area

Guantanamo Province

CUBA

20°10'00"

74°55'20" 74°43'39"


3.1.2 Climate

The study area has a very dry tropical climate with two pronounced seasons: dry and rainy season. The average rainfall per year is about 600mm. The whole area is covered by vegetation, its composition de-pending on the climate, lithology, relief and soil. It is also possible to differentiate vegetation in three main zones: coastal, mountain, and valley. In the coastal zone the biggest diversity of cactus and succulent plant of Cuba are present. The mountain zone it is characterised by very exuberant Caducifolious forests and very well developed plants above limestone. Inside the valley a different microclimate conditions exists and one can find very highly cultivated lands. The temperatures oscillate between 35 and 38 C.

3.1.3 Geomorphology

The geomorphology of the area is rather complex. The neotectonic movement in the area as well as the posi-tion of the sea level contributes to the relief of the study area. As result of neotectonic uplift (of moderate and strong of amplitude, from 300 to 2000m), the morphology is predominantly controlled by structure with low mountain (form 1000 to 1500m), small mountain (from 500 to 1000m) and hills (from 300 to 500), being present which are a result of the different phases of tectoic uplift. Figure 3.1.2 Main geomorphological features of the study Area. (Anaglyph. Castellanos,2000)

In general, the relief is predominantly hilly and moun-tainous with one central valley surronded by high mountains and intramontain valley parrallel to the coast. The Caujeri valley is located in the central part of the study area. In the area there are mountains, which can morphogenetically be cosidered as system of blocks in complex folds. Examples include: Sierra del Purial to the north and east, El Convento to the SouthEast (Cañete et al. 1997). Sierra de Caujeri

mountains to the west, and Sierra de Mariana and Sierra de Baitiquiri to the south. The San Antonio valley lies to the south (Fig. 3.1.2). The drainage is very developed in the center of the valley, but in others part, most of the times the secondary streams have dry riverbed. The waters of the main river Sabanalamar, drains toward the South. Well developed dendritic drainage pattern can be seen in the Northeast of the area and very good karst formation in the West of the area.

Caribbean Sea



3.1.4 Seismic Activity

The earthquake epicenters as collected by the sismological station in the eastern part of Cuba are shown on Fig 3.13. The seismic activities in the area in general are produced by plate boundary. It is very well de-veloped in the marine zone on the South part of the whole Oriente province. These activities are condi-tioned by interaction between North-American plate and Caribbean plate. The principal axis is located in the Bartlett-Caiman fault zone. The magnitude of the earthquake can be more than seven.

Figure 3.1.3 Map with epicenters of earthquake, collected by the sismological station in the eastern part of Cuba, from 1979 to 1988 periode. (After Cañete et al. 1997).

3.2 Geology of the Study Area

The Eastern part of Cuba, where the study area is lo-cated, is identified as the Neotectonic East province of Cuba. The geology of the San Antonio del Sur is more com-plex than described in previous published papers and Geological maps such as 1:250 000 scale map of the whole Oriente, prepared by Academies of Sciences of Cuba and USSR, (Nagy et al. 1976) (Figure 3.2.1), and 1:100 000 scale map of the approximately 70 % of the area prepared by geologists from Cuba and USSR. (Nu-ñez et al. 1981) (Figure 3.2.2).

Figure 3.2.1 Geological map as result of geological map-ping 1:250 000 scale. Taken from the whole Oriente map, prepared by Academies of Sciences of Cuba and USSR, (Nagy et al. 1976)



Figure 3.2.2 Geological map as result of geological mapping 1:100 000 scale. Here about only 70% of the study area is covered. The map was prepared by geolo-gists from Cuba and USSR. (Nuñez et al. 1981) To the west, it has boundary with the Guantanamo basin, which has very thick Paleogenic volcanic and sedimentary sequences. To the North and East, with the metamorphic rocks of Purial massif and to the South with the fault zone, which is a boundary of the Bartlett trench, with deep of 4-5 Km, which has oceanic crust. (Cobiella, et al. 1977). As in all Cuban archipelago, the geological compo-sition and structure of the area consists of two main structural levels: the foldbelt and the neoautochton (Iturralde-Vinent, 1994).

3.2.1 Stratigraphic features

The Foldbelt

Pre-

pale

ocen

o

Sierra del Pu-rial Formation

Serpentinite of Sierra El Convento

Mid

dle

and

Lat

e Eo

cene

San Luis Formation 600-700m

San Ignacio Formation more than 300m

Mid

dle

Eoce

ne

The foldbelt is composed of deformed and metamorphosed continen-tal and oceanic units. It represent more than 60% of the whole area, as Ophiolite, Puriales complex, El Cobre formation, Charco Redondo formation, San Ignacio formation and San Luis formation. (Figure 3.2.1 and 3.2.2) Puriales complex Around 40% of the area are Sierra del Purial metamorphic massif, formed by Cretaceous metavolcanic-sedimentary rocks (Figure 3.2.1, 3.2.2). Some workers considered this before as an exposure of the crystal crust of Cuba, with upper Prejurassic and even Paleozoic age (Furrazola et al. 1964, Pushcharovski et al. 1966, Khudoley and Meyerhoff 1971, Pardo 1975). Figure 3.2.3 Stratigraphic column of foldbelt. (Modified from Cobiella et al. 1977)

They did not differentiate these metamorphic rocks into different



units. Later Somin and Millan (1972, 1981) made differentiation of the metamorphic rocks in different complex of Mesozoic age, which juxtaposed due to tectonic movement. A more detailed characterisation of metavolcanic-sedimentary complex of Purial was made by Boiteau et

al. (1972), who interpreted it as an ophiolitic complex. They attributed the origin of the complex to high-pressure metamorphism and they reported the existence of a metamorphic zonation, with one zone of glaucophane-lawsonite facies and another greenschist facies. Boiteau and Michard (1974) described three superimposed state of deformation for these metavolcanites.

Figure 3.2.4 Geological-schematic Map of metavolcanic cretaceous Purial Complex. The distribution of de-scribed metamorphic sequences are aproximatly shown by varying patterns. (After Millan in: Iturralde-Vinent 1996). The rocks of metavolcanic-sedimentary complex were named as La Farola formation (Nagy et al. 1976, 1983), with insufficient details. The same was the problem with the Sierra del Purial Formation estab-lished by Cobiella et al (1977), because it has even more different units and complexes. Based on previous research and work of Millan and Somin (1985), the last characterization of the Purial complex was done (Millan in: Iturralde-Vinent 1996). The characterization of this complex to-date how-ever is far from complete. It was named in an informal way as Purial complex and was unconditionally differentiated in different sequences whithin the massif. These sequences were named as Quivijan, Jojo, Rio Baracoa, Via Mulata, y Mal Nombre, (Millan in Iturralde-Vinent 1996) (Fig.3.2.4). In this study, only the Quivijan, Via mulata and Mal Nombre sequences will be discussed. Quivijan Sequence It was described by Millan and Somin (1985) in the Northwestern part of Sierra del Purial. It is chiefly composed of volcanic rocks without metamorphism or with very low grade of metamor-phism. The main rock type present is psamitic tuff, tuff-breccia not well stratified, with basalt py-roxene-plagioclase fragment, with porfiric structure and amigdaloid texture and with fragments of clinopyroxene crystal and magmatic plagioclase. In this sequences one also encounters inter-bedding of banded tuffites which are very fine grained showing bands of different colors and fre-quently schistose. The grade of crystallisation of this vulcanite is very low to the extent that one can possibly find volcanic glass. The sequence also shows evidence of zeolitization and partial prehnitization. In some places green rocks are mapped constituting of actinolite (because of magmatic clinopyroxene), and with abundance of epidot, prehnite, and pumpelleite (Millan in Iturralde-Vinent 1996).



Via Mulata Sequence

It was described for the first time by Millan (Millan in Iturralde-Vinent 1996). It is distributed in the Northwest part of the Purial complex. Here there is a characteristic an interlayer well stratified meta-tuffites with the stratification sometimes being cyclic in nature. It is easy to recognize the full range be-tween psamitic meta-tuff to very fine grained meta-tuffites, possibly metapellite. In general the sequence has shale shape and shear surface with green to more dark colors. In different part of the sequence it has interbedding of light colour shaly limestone and some layers of amigdaloid metabasalt. Coarse grain metatuff can also be present.

Mal Nombre Sequence

Again, this sequence distributed in the Northwest of the Purial complex, it was described for the first time by Millan (Millan in Iturralde-Vinent 1996),. These consist in polimictic metasandstone, generally homo-geneous, massive or poorly stratified. Generally they range from coarse grained rocks to metaconglomer-ate-breccia. The fragments are poorly sorted and generally very angular. The green colour is the frequently colour of these sequence. At some places interlayers of very fine grain are present. The internal composition of Purial Complex is quite variable. It includes Cretaceous volcanogenic – sedi-mentary rocks, ranging probably from Albian to Campanian age, determined on the basis of paleontologi-cal data and an approximate correlation with the formations in Camaguey province which have the same lithological composition. The Purial complex is the only one place where it is possible to find outcrops of cretaceous volcanic arc metamorphosed under these specific Pressure/Temperature conditions.

Ophiolite

The Ophiolite in the area is represented by Sierra del Convento mountain. This mountain ophiolite com-plex is interpreted as an allocthonous serpentinite body thrusting cretaceous metavolcanite of Purial com-plex (Knipper and Cabrera 1972, Boiteau et al. 1972). These were described as garnet-amphibolite by Co-biella et al. (1984). Millan in Iturralde-Vinent 1996 described it as serpentinite with inclusions of high- pressure metamorphics, with blocks of metasilicite-schist quartzite, and intercalation of green schist. The metaophiolites of high pressure are related to a subduction complex (Millan and Somin 1985b).

Figure 3.2.5 Generalised geological map and cross section of the eastern part of Cuba.

In eastern Cuba, the ophiolite thrust-sheet is up to one km thick and rests subhorizontally on Cretaceous backarc volcanoclastic (After Iturralde-Vinent, 1996).



El Cobre formation

The El Cobre formation was defined by Taber (1934). In the study area this formation is distrib-uted in the North-central part. It is a resultant of Paleogene volcanic arc, and ages from Paleogene to Middle Eocene. It is represented by different types of volcano-sedimentary rocks, tuff, lava, agglomeratic tuff, lava of andesite and dacite composition, rare rhyolite and basalt composition, interlayered of tuffites and limestone, graywake and polimictic sandstones. This formation tec-tonic overlies Purial complex cretaceous metavolcanite, as well as San Luis and San Ignacio for-mations. These volcano-sedimentary deposits were deposited in shallow to moderate marine en-vironment. The thickness of deposition is around 5000m. (Franco et al. 1992).

Charco Redondo formation

It was defined by Woodring and Daviess in 1944, and redefined by Nagy in: E. Nagy et al. (1976). In the study area this formation is found in the north central part and at some place in the East central part of the Caujeri valley. Lithologically it is characterised by massive often light coloured limestone, biodetritic and fossiliferous limestone. Frequently one can find breccia, showing thick coarse stratification. Charco Redondo formation unconformably overlies El Cobre formation, and Purial complex. San Luis Formation unconformably overlies this formation. The age attributed to this formation is Middle Eocene, and the de-positional environment is typically shallow water, littoral or sublittoral. These are as synorogenic deposits and the sequences were developed as a piggyback basin of Paleogene Volcanic Arc. It’s thickness ranges from 50 to 200m. (Franco et al. 1992).

San Ignacio formation

It was described by Boiteau and Campos in 1974. Its distribution in the area is restricted to a very thin belt along the Sierra del Purial border. It is characterized by polymictic breccia with very poorly sorted rough clastic material, such as green schists, phyllite, and serpentinite, with very little cement clayey. San Igna-cio formation unconformably overlies Purial Complex and this formation is unconformably overlain by San Luis and Miocene deposits (Fig. 3.2.6). Middle Eocene upper part age. It is a slope deposit combined with submarine scarp of probably tectonic origin. Thickness in generally is less than 700m (Franco et al. 1992).

San Luis Formation

It was defined by Taber (1934) and redefined by Brezsnyánsky in: E.Nagy et al.,1976. It is a very widely occurring formation in the area. It is characterized by polymictic sandstone, lutite, marl, clay, clay lime-stone, biodetritic limestone, polymictic conglomerate and in general shows very good bedding. Toward the top of the cross section the amount of clastic material arises and the deposits are folded. San Luis for-mation is found lying unconformably over formations Charco Redondo, San Ignacio, Purial complex and El Cobre. This formation is unconformably overlain by Cilindro and Maquey formations (Fig. 3.2.6). Age



assigned is Middle Eocene (upper part) to Upper Eocene. At the beginning the deposition of this formation took place in deep marine water that later changed to deposits of shallow water. Thickness estimated by previous works is about 700m (Franco et al. 1992).

Figure 3.2.6 Schematic Cross section for sedimentary sequences along the study area. (After Franco, 1983)

The Neoautochthon

The neoautochthon is composed of latest Eocene to re-cent slightly deformed sediments, which have not been displaced since deposition. It represents the other 40% of the area. It contain different units such as Cilindro Formation, Maquey formation, Yateras formation, Rio Maya formation and Recent deposits which can be dif-ferenciated by genesis as elluvial, colluvial, prolluvial, alluvial and marine deposits.

Maquey Formation

Cilindro Formation

Yateras Formation

Rio Maya Formation

For the whole region were recognized three transgre-sion- regresion periods in the evolution of the sediments. The first started on the Latest Eocene and finished on the Oligocene, the secound started in the Lower Miocene and finished in the Late Miocene and the third one which started at Pliocene to Recent.

Figure 3.2.7 Synthetic Stratigraphic column of Neoautochthon. (After Calais and Lepinay,1995)

Cilindro Formation

It was defined by Brezsnyánszky and Franco in: E. Nagy et al. (1976). In this study area this formation is developed in several places, in most of the cases inside the Caujeri Valley, in the North. It is characterized by polymictic conglomerate with lens stratification and some place cross bedding, interbedded with sand-stone and lignite, different colour. The Cilindro formation unconformably overlies San Luis, Purial com-plex, and San Ignacio formations. This formation is uncorformably overlain by Yateras and Maquey For-



mations (Fig. 3.2.6). Upper Oligocene to lower Miocene. It was deposited in delta environment and sublit-toral. Thickness estimated is about 10-20m (Franco et al. 1992).

Maquey Formation

This formation was described by Darton (1926). It is very well developed in the area specially outside the Caujeri Valley. This formation contains different types of rocks with interbedded layers of sandstone, lu-tite, gray calcareous clay, white marl with interbedding of biodetritic limestone, fine stratification, rarely thick or massive. In some layers specifically in the lutite and biodetritic limestone, very large Lepido-cyclina are easily found. In other layers gypsum, lignite, and lignitized remains of vegetation are found. Maquey formation unconformably overlies San Luis and San Ignacio formations. In other part also this formation overlies ultramaphic rocks. This formation is uconformably overlain by Rio Maya formation and it is conformably overlain by Yateras formation (Fig. 3.2.6). The age assigned is Upper Oligocene to lower Miocene. In the base of this formation, the predominatly depositional environment was sublittoral with moderate energy, and limited development of coral barrier reef. It is characterized by the association of Lepidocyclina – Corallinaceae. In some places the depositional environment is identified as lagoonal with local variations. The top of the formation shows marine oscillations from sublittoral to lagoon with fluvial influence. The thickness is more than 700 m (Franco et al. 1992).

Yateras Formation

This formation was described by Kozary (1955e). It is very well develops and in general forms the top of all mountains in the West and South of the area till Sierra Mariana. This formation is characterised by interlayering of fine to coarse grained detritic limestone; biodetrite and biogene showing fine to coarse stratification, with variable porosity, some times very massive, and containing large Lepidocyclina. In general the rocks are whitish or light pinks in colour. The Yateras formation conformably overlies Maquey Formation, and unconformable overlies Charco Redondo, San Ignacio and San Luis formations (Fig. 3.2.6). Quaternary marine and terrigenous deposits cover these rocks. The age assigned is Lower Oligo-cene to Lower Miocene. Marine carbonate and reef deposits represent this formation. The thickness is be-tween 160 and 500 m (Franco et al. 1992).

Rio Maya Formation

This formation was described by Franco in: Nagy et al. (1976). It is a very well developed formation, forming a discontinuous belt in the coastal zone of the study area. Biohermic algaceous, coralineous and micritic limestone, containing abundant insitu corals, and also fragments of corals such as Acropora pro-lifera. Dolomitic limestone is also frequently found. The clay content is not constant. Polimictic conglom-erate with fine to medium grained and calcareous cement is intercalated at different levels. It is generally white, yellow, pink or gray in colour. The Rio Maya formation is found lying unconformably over Ma-quey, San Luis formations and Purial complex, which is subsequently overlain by Quaternary marine de-posits. The age assigned is Late Pliocene to Lower Pleistocene. These deposits were formed in reef envi-ronment with influence of periodic more energetic episodes. This is exemplified by the presence of coarse



terrigeneous clastic materials, and Amphistegina – Archaias bentonic association. The thickness is be-tween 30 and 80 m. (Franco et al. 1992).

Recent deposits

These are very well developed horizontal to subhorizontal deposits, which lie unconformably over all oth-ers older deposits. On the bases of genesis these could be characterised as elluvial, colluvial, prolluvial, alluvial and marine deposits. Karst elluvial deposits are dark red colour deposits, which can develop only in the top of limestone with which they have direct genetic link. Generally the thickness can be less than 1m. It is very well developed above Yateras Formation, in the Sierra de Caujeri mountain. Due to the weathering process there are also red colour elluvial deposits in the top of the mountain which belong to metavolcanite of Sierra del Purial complex with existence of kaolinite and others clay minerals. Colluvial and prolluvial deposits are very well developed in the area along the slope of the mountains, formed by rock fall and landslide. They contain breccia with fragments of rocks, sands, and terrigenous materials. In the West edge of the Caujeri Valley appears a big concave scarp, which suggests the presence of a big landslide or sequences of landslides. As a result of these landslides there is a large quantity of col-luvial and prolluvial deposits inside the Valley. This material is also appearing increasy as a result of the neotectonic activity in the area. Alluvial deposits are represented by riverbed facies, coarse material and sands with cross stratification; and clay sands, clay and silts, with poor or no visible stratification. The component materials are closely related to the original source, which can be polymictic. In the case of clastic material the source rock can be limestone, serpentinite, metavolcanite and others rocks. Marine deposits are developed along the coastal zone, they are characterised by coraliferous limestone and calcareous conglomerates, sands and very coarse material, fragments from different sources such as metavolcanite, serpentinite, limestone and others.

3.2.2 Structural and tectonic features

The structural setting of the study area as concluded by earlier workers is presented in this section along with the author’s own view on this aspect. However the detail analysis and interpretation of the structural trends in the study area are further presented in the Chapter 5. From the tectonic and structural point of view it is very difficult to recognise the structure in the metamor-phic massif of Purial Complex, due to the very monotonous composition of sequences. To study the de-formation fold trends in the study area it is more useful to follow the visible structures of marble, which outcrop at Loma La Fuente hill in San Antonio del Sur. Three superimposed deformation phases were recognized by Cobiella et al. (1977). The first or oldest de-formation phase is often very difficult to observe these folds because they were affected later by other forces. However it is possible to see the original schistosity and the crenulation lineation in some outcrops.



During the second deformation cycle the schistosity and the lineation of the first one, were folded, but dur-ing this derformation the schistosity was not developed fully, only very locally. In this case the folds are similar, close, with NE-SW orientation. The style of the the third deformation folds are very different in relation with the previous two, they are represented by very big radius and low amplitude of curve, and folds type kink-band, which are crossed by many shear planes. Acording to Cobiella et al. (1977) the sec-ond deformation phase was deformed by the third one, but the orientation of folds axis remained the NE-SW. As result of the present work four deformation phases were recognized, they will be explained in Chapter 5. In the metamorphosed tuffs these deformation phases are not well visible, but they also could have the same deformation phases as the marble, because they are interbedding layer in it. The relationship between these three deformation phases (in the schists and marble) with the metamorphic process suggests that they occur during the same orogenic activity, because the rocks have the same metamorphic facies (Cobiella et al. 1977). The serpentinite of Sierra del Convento Mountain to the North tectonically lies above the schists of Sierra del Purial Complex, with almost horizontal contact, it was interpreted as a thrust fault (Cobiella et al. 1977). To the West the serpentinite has a tectonic contact with schists of Purial Complex by strike slip fault, which follows the Sabanalamar River. To the East there is almost the same situation with amphibo-lite, tectonic contact with similar type of fault, which fallow the Macambo River. Along all contacts there are many tectonic blocks of schists, with polymetamorphic characteristics. These tectonic inclusions suggest very complex metamorphic history. The presence of these rocks in the serpen-tinite also suggest about formational condition of them, that it is very possible they were deformed and later after they were emplaced, probably from the South, during Paleocene or latest Maastrichtian. (Co-biella et al. 1977) (Fig. 3.2.10). Due to the orogenic movement of Middle and/or Late Eocene, and because of the Paleogene Volcanic Arc, were tectonically emplaced the rocks of Cobre Formation, above the San Ignacio and San Luis deposits. The allochton movement was directed from South to North. And these proofs the presence of continental crust blocks in pre Oligocene time, in the place where now is located the Bartlett basin. (Cobiella et al. 1977). The San Ignacio and San Luis formation sequences are characterized by a monoclinal gentle folding structure. In San Ignacio formation it is very difficult to recognise the structural features, because of the particular genetic origin, these sediments has not stratification. The San Luis formation covered with very slight angular uncon-formity the San Ignacio Formation; it was demonstrated



by the very rapid change in thickness of the San Ignacio Formation, which even in some place disappear as deposits (Cobiella et al. 1977). Figure 3.2.8 Reconstruction of the possible premiocenic position of Eastern Cuba and Santo Domingo, showing the location of some commune geological elements. (After Cobiella et al. 1984) In generally the southerner terrigeneous Oligocene deposits of the study area, are likely to came from the erosion of similar to San Luis volcanic sequences, located to the South of the sedimentation basin. These facts suggest the transformation sinistral character of the Oriente fault, which detached the Hispaniola ter-ranes from Eastern Cuba. (Fig. 3.2.8) Actually the Oriente fault is the most important tectonic feature that has very strong influence in the evolu-tion and structural development of the area. This fault evolved in two stages: first by Late Eocene-Oligocene sinistral strike-slip displacement with deformation along the trend of the fractures; and sec-

ondly, during the Miocene-Recent, with sinistral strike-slip and extensional displacements (pull-apart basin formation) (Fig. 3.2.9).

Figure 3.2.9 Plate motion vectors of the Caribbean Plate relative to the North American Plate along the northern Caribbean Plate boundary. (Taken from Calais & Lepinay, 1995)

As a consequence, the pre-Miocene rocks in the area are strongly deformed while the Miocene and younger deposits are horizontal or only slightly tilted monoclinal toward S-SW, and have been uplifted more than 200 meters above sea-level (Iturralde-Vinent, 1996). It is possible to find layers of the Miocene in some places dipping toward W-SW (Cobiella et al. 1977).


CHAPTER 4. DATA INPUT AND METHODOLOGY

Chapter 4: Data input and Methodology

The present study intended generation of geological and structural maps of the San Antonio del Sur area and development on some ideas on the tectonic evolution of the area. To achieve this, it was essential to use combination all the available data, through processing, enhancements of the original data and combi-nation using data integration techniques.

4.1 Data used

Different datasets were used in studying the area. Some of these data were obtained in digital format while others were not. The data can be classified into remote sensing, ancillary and field data.

4.1.1 Remote Sensing Data

All data or information about the study area can be obtained using Remote Sensing Techniques. These include satellite or aerial photographs obtained without actually having physical contact with the object. Several satellite images from different sensors were used in this study. Window representing the study area was selected from the main frame. The specific image data sets consisted of: • Spot image: (FRANCE SPOT Date: 28/12/1994). A panchromatic image covering the whole area,

with a 10m spatial resolution in digital format. • Landsat TM image: (LANDSAT-TM; Date: 01/15/1985) Landsat Thematic Mapper (band

1,2,3,4,5,6,7) image covering the whole area, with a 30m spatial resolution, an exception being band 6 with a resolution of 120m, all in digital format.

• SAR image: (JERS-1 HH; Date: 01/05/1994). The Radar image used for the research covered the whole area. It was made with a synthetic system with a ground resolution of 15m with polarisation horizontally emitted and received (HH). The data was in digital format.

• Aerial photograph: (Fly K-10; Date: 1970), scale of 1:37 000. The whole area is covered by 8 flight lines with a total of 93 photographs, which have more than 60% overlap and enough sidelap (more than 30%) to get a stereoscopic view of the terrain. This stereoscopy was very useful for interpretation purpose. The large-scale photos also enhance the features, which becomes easily detectable. The pho-tos were in hard copy.

• Geophysical data: Data from Aeromagnetic mapping scale1: 50000, for the whole country, made in 1980. The data consist of Aeromagnetic anomaly surface and radiometric maps, the latter representing anomalies of U, Th, K in digital format.



4.1.2 Ancillary Data

In this research, use was also made of various existing other datasets, which include: • Geological map: In the study area, as in the whole Oriente province, a geological mapping at scale of

1:250 000 was carried out in 1976, by Academies of Sciences of Cuba and USSR, (Nagy et al. 1976). Later on in 1981 geologists from Cuba and USSR mapped part of the area (approximately 70%) at the scale of 1:100 000. (Nuñez et al. 1981). In the present research the geological information from both maps were used, as well as the structural measurements taken by those geologists.

• Topographic map: Topographic sheets of the area, at a scale 1:100000 and 1:50000. Of the Institute

of Geodesy and Cartography of Cuba (ICGC), dates of 1985, with contour line intervals of 20m each, were used.

• Information from different papers written by specialist who have worked in the area before: To

be able to execute the set objectives it was necessary to carry out an in-depth evaluation of the existing material and papers, indispensable for development of this research. Once identified, revised and ac-quired it was possible to proceed to use them in each work phase. All papers and publication used are listed as References and consulted bibliography at the end of the Thesis.

4.1.3 Field Data

Fielwork involved the collection of various informations regarding the geology, structure, stratigraphic relationship between different units, different deformation phases and evidences related to neotectonic ac-tivity of the area. These are elaborated in Section 4.2.3.



4.2 Methodology

Fig. 4.2.1 shows the flowchart adopted in the study area during preparation fieldwork, Data integration and data analysis stages.

Figure 4.2.1 Flowchart of Applied Methodology

In the Preparatory Stage, inputting, preprocessing and processing of data from different source was carried out. To implement all these actions, ILWIS software, version 2.2 was used. Detailed explanation is given in Sections 4.2.1. and 4.2.2. The hard copies of Geological maps in scales of 1: 250 000, and 1: 100 000 were digitized, following the procedure of ILWIS software. To obtain segment maps, attention was taken to use the proper domain and representation of different segments. After the topology or segment checking process, the maps were con-verted to polygon maps, and used as reference for previous work and base geological map of the study area. The hard copy of topographic map in scale of 1: 50 000 was used as a base map for the research. In order to make a Digital Terrain Model (DTM) of the area, the standard DEM generating procedure in ILWIS was used. The contour information on existing topographic map was digitized and the segment map con-



verted to raster, using defined georeference for the study area. The linear interpolation was made between the pixels with altitude values to obtain the elevations of the undefined values in between the rasterized contour lines. Later on, the DTM was used to create several shadow maps, showing the terrain under an artificial illumination for structural interpretation and other products (see section 4.2.4). The interpretation of aerial panchromatic photos in the scale 1:37 000, was also entered in digital format, using the standard input module of ILWIS. The obtained polygons map was used for the analysis and to update the geological map.

4.2.1 Preprocessing of Remote Sensing Data

In the case of satellite images, at the preparatory stage image rectification and restoration was done in or-der to correct distorted or degraded image data, so as to create a better representation of the original scene. This involved initial processing of raw image data to correct for geometric distortion, calibrate the data radiometrically, and to eliminate noise present in the data. These operations are often termed preprocess-ing operation because they normally precede further manipulation and analysis of the image data to extract specific information. The georeferencing of the SPOT image was done using reference point method in ILWIS software. In this case the corner co-ordinates of the image were unknown. Using the topographic map of the area as a refer-ence map, we found several identifiable points on the image as well as on the map. The obtained 7 points were used to derive a polynomial transformation of the first order, affine transformation, with final sigma value of 0.2 pixel. The resampling of the image was later done for its geo-coding using Nearest neighbour interpolation method. The georeferencing of the Landsat TM and Radar raw satellite image were done using image-to-image registration methods. In both cases the geometrical corrected SPOT image was used as the master image, because of its high quality and high spatial resolution. After the introduction of 7 and 16 points respec-tively, the points were used to derive a polynomial transformation of the first order, affine transformation, with final sigma values of 0.2 pixel and 3.5 pixels for TM and Radar respectively. After this they were resamplied for geo-coding using the Nearest neighbour interpolation method. The atmospheric effects can influence the radiance measured by any sensor. They have effects on the ori-gin through the attenuation of the radiation in the atmosphere and the dispersion of this radiation is de-pendent on the wavelength, the smaller the wavelength, the higher the dispersion (Lillesand and Kiefer, 1994). In this study radiometric correction was done using the standard “dark object subtraction” approach of Chavez (1988). The values to correct for in each band were the following: Band 1: 70, Band 2: 19, Band 3: 12, Band 4: 5, Band 5: 3 The formula used to subtract these values was:


Band with Atmosph. Correction = Band with Geometric Correction – Value


A confirmation method that the position is correct is obtained by looking at the values where it decreases with increasing wavelength. The satellite image interpretation is very useful for providing a regional overview of the geological and structural features present in the study area, especially during the first stage of the study. In this stage the interpretation is important in order to recognise the regional structural trends and styles. It is also useful to trace the outcrop patterns and the extent of the major lithostratigraphic units. However applying image enhancement techniques help in making the image interpretable for these purposes, easier for the above mentioned features. For the Landsat TM image, spatial enhancement was carried out by using high-pass filters in order to en-hance the edges. Two types of high-pass filter directional and Laplacian were used. The first in order to enhance the diagonal linear trends NW and NE directions and the second in order to enhance linear fea-tures having almost any direction in the images. The Landsat images in some areas were very dark and in other very bright. In order to improve the contrast of the image in certain places, the technique of selective contrast en-hancement was applied, where en-hancement of the images was based on statistic of two windows made in both extreme parts of the images (Fig.4.2.2). This technique gave the possibility to better observation of the lithological boundaries of some units.

Figure 4.2.2 Selective contrast image enhancement



4.2.2 Processing of Remote Sensing Data

During the Preparatory Stage, several image processing techniques were used in order to improve the data and visualisation of the geological and structural features (Fig. 4.2.3). The false colour composit was created using the bands offering the optimal information necessary. The false colour composite using TM bands 7,3,1; 4,5,3 and 7,5,4 (in RGB order) were found to be aestatically appealing and the most usefull for extracting information regarding the various lithological and structural elements.

Figure 4.2.3 Images Processing Techniques .

To enhance or extract features from satellite images, which cannot be clearly detected in a single band, it was important to use the spectral information of the object recorded in multiple bands. These images may be separate spectral bands from a single multi-spectral data set, or they may be individual bands from data sets that have been recorded at different dates or using different sensors. The operations of addition, sub-traction, multiplication and division are performed on two or more co-registered images of the same geo-graphical area. In this study several multi-band operations were made in the preparatory stage such as: ra-tio images, normalised difference vegetation index, principal component analysis, and image fusion.



Ratio images are often useful for discriminating subtle differences in spectral variation, in a scene that is masked by brightness variations. Different band ratios are possible to give the number of spectral bands of the satellite image. The Puriales de Caujeri sector has mountain areas, thus applying band ratios to sup-press topographic effects on illumination is very useful. In this case band 5 was divide by band 4 of Land-sat TM. To suppress effect of vegetation band rationing using near infrared and red in the visible range of the spectrum is used. However applying normalised index, (eg. normalise difference vegetation index (NDVI) for the area) was more useful because with this method, not only could the effect of vegetation be subdued, but also possible to get compensation changes in illumination conditions, surface slopes and as-pect (ILWIS 2.1). The operation involves subtraction of band 3 from band 4 and then dividing by their sum. Principal components analysis is another method applied to compact the redundant data into fewer layers, and to transform a set of image bands, to new layers not correlated with one another. Because of this, each component carries new information. The component are ordered in terms of the amount of variance ex-plained, the first two or three components will carry most of the real information of the original data set, while the later components describe only the minor variations. The principal component one, from the combination of all bands, was used for extracting the structural feature from the image. Principal compo-nents analysis using combination of bands 2,4,5 and 7, the RGB colour composite in which component 4 is displayed in red and component 2 and 1 in green and blue respectively. As well as using combination of bands 1,3,4 and 5, the RGB colour composite in which component 4 is displayed in red and component 2 and 1 in green and blue respectively. It was used for the lithological discrimination, taking advantage for the first case, the differences in hydroxides content was useful for mapping the terrigenous units and in the second the different content of iron of the units was useful for mapping the ophiollite and different meta-vulcanite. Image Fusion is the process of combining properly co-registered digital images, by modifying the data values, using a certain procedure. Commonly used technique is the red-green-blue transform into inten-sity-hue-saturation, the intensity component is commonly replaced with another image and the modified data set is transformed back into the three primary colours. (Harris, J.R et al. 1990).

SPOT image I

H

S

R

G

B

IHS transformed

SPOT\Landsat TMimage

Tra

nsfo

rmat

ion

RGB Landsat TM (Band 7,3,1) (Band 4,5,1)

In order to improve the resolution of the Landsat TM image, for the colour composite CC731 the intensity of TM bands component was replaced by the SPOT panchromatic image (Fig. 4.2.4) with resolution of 10m. (See section 4.2.4)

Figure 4.2.4. Methodology for integration Spot and Landsat TM



4.2.3 Field Data Capture

In the Preparatory Stage, all literature review and inventory of the types of data from previous works was carried out to assist fieldwork requirements and the selection of geological traverses. To facilitate the field data capture, a database structure was designed in advance. During the Fieldwork Stage the verification of the previous interpretation made during the preparatory stage was carried out together with the following tasks: • Approximately 140 observation points were visited, major and important lithological boundaries were

checked and established. • To understand the geology and structure of the area, three representative cross sections namely: W-E

across the Caujeri Valley, the second SW-NE across the Caujeri Valley and the third along the highly deformed metavolcanite of Sierra de Puriales Complex were made. Measurements of structural fea-tures on different units were done, and their stratigraphic relationship established.

• Structural trends were analysed and different deformation phases present in the area were studied.

Evidences for time relation were established and some evidences to understand the neotectonic movement in the area were collected.

• All the data were inputted into a structured database in the field to facilitate and simplify processing

and analysis, using Fieldlog, a public domain software developed at the Geological Survey of Canada for storage, display, and export of geological field data. Structural data was inputted using an already existing list of symbol incorporated in this software. This is very useful for plotting and representation in later data integration and analysis.

4.2.4 Data Integration

With any Geographic information Systems (GIS) the data extracted from any other system can be incorpo-rated into a geographic data base applying GIS techniques. Almost all systems purporting to be Geographic Information System can provide a graphic overlay where one theme or layer of information is graphically portrayed over another. Very often this visual integration is sufficient. However, if the requirements are for analysis, then geoprocessing tools for compositing two or more themes or layers are necessary. Similarly, different remote sensing system, looking at the earth at different wavelength, resolution or times, can combine to provide better or different information than any sensor used alone. The use of dif-ferent types and scale of satellite images and aerial photographs during the preliminary stage of this work led the author to get more lithological and structural information, which could be extracted from different types of images of the study area. Different products of interpretation were also created.



The interpretation of Landsat TM image using different products of image processing provided the lithological information on the exposed rock units in the area. From other products such as Principal com-ponent one, all major structural features were well extracted. The interpretation of the SPOT panchromatic image improves the boundary of the units delimited using the lower resolution TM image. There were no significant differences in regional structural interpretation based on either SPOT or Landsat image. Other features such as main roads, drainage, and topographic de-tails were much more detailed on the SPOT image than the TM image, and SPOT thus used with DTM (Anaglyph) to extracted structural features, using the 3D capability of ILWIS. All lithostratigraphic rock units, local structures and different geomorphological features are fairly distin-guishable on interpretation from pancromatic aerial stereophotopairs, which were used to make detailed photogeological map of the study area. The fold structures are easy to identify where bedding attitude is clearly depicted in areas less covered by vegetation. In order to integrate remote sensing data from aeromagnetic survey with the satel-lite images, image fusion process was per-formed using ILWIS software IHS trans-formation. For this purpose the high reso-lution radar data as well as SPOT pan-chromatic image were used to modulate intensity while the lower

Aeromagnetic data

Synthetic file DN=150

Radar image I

H

S

R

G

B

IHS transformed Ra-dar\aeromagn

image etic

Tra

nsfo

rmat

ion

Figure 4.2.5 Methodology for integration Radar and Aeromagnetic data

resolution geophysical data were used to provide image hue, with previous co-registration of all data to the same georeference, with pixel size of 10m. For the saturation, a synthetically generated file was used and assigned a DN value of 150 to ensure a proportionate mix of the radar and magnetic data and to provide hues that were less vibrant (Harris, J.R et al. 1990). These three IHS components were then reverse trans-formed to RGB space to produce the viewable image product. In this integration the radar and SPOT im-ages provide the recognisable image of the terrain surface, that facilitates in the case of radar a comparison between topographic and geophysical patterns. At the end, results in more detailed and accurate geological and structural interpretation were obtained. (Fig. 4.2.5) In the previously enhanced image, the geological and structural elements were possible to study. For each major stratigraphical or lithological unit, lithological boundaries were on-screen digitized taking image characteristics into account. Based on data acquired in the field, relevant geological information recorded in digital database such as structural measurement, rock type unit, spectral response, etc. were retrieved and plotted as a map. Digital vector geological map was overlain on top of each resulting previously processed image.



The integration of database results from fieldwork with interpretation was done later by overlaying the thematic point maps with information of geological units, contour map from interpretation and images. After rectifying the boundaries, the geological map was updated taking the field data and photo character-istics into account. Lineaments were traced by on-screen digitizing on the edge-enhanced remote sensing data and products obtained from DTM (see 4.2.1 topic) were integrated to form the lineament map based on satellite image and topographic features interpretation. Lineament analysis was performed by means of rose diagrams and fracture maps generated from images, aerophoto and DTM data. Field data on fracture characteristics were analysed using rose diagrams, stereographic projections and maps. Structural analysis of different deformation phases by means of folds, faults and shear zones, was carried out to develop ideas about the tectonic evolution of the area.


CHAPTER 5. DATA ANALYSIS RESULTS AND INTERPRETATION

Chapter 5: Data Analysis Results and In-terpretation

5.1 Introduction

In this chapter the analysis and interpretation of data sets used in this research are presented. It includes detail geological and structural description of characteristic cross sections through the area; structural analysis based on the field data collected; observation and evidences directed towards a complex tectonic setting of the area and Neotectonic activity. Some ideas about the tectonic evolution model for the area (developed based on the analysis of results) shall also be given.

5.2 Geological and structural Section

In order to give a detailed description of the geology and the structure of the area, geological and struc-tural fieldwork observation, updated geological map (appendix 1) and three schematic profiles traced along the area in different directions were considered. These were: W-E across the Caujeri Valley, the second NNW-SSE across the Caujeri Valley and the third along the highly deformed metavolcanite of Si-erra de Puriales Complex. The cross sections were selected in such way that the main units described in the area appeared, as well as the different structural domains, thus enabling this way to present the data and evidences that were used by the author for the final analysis in the contiguous sections. While describing these three cross sections a complete description of all the formations present in the study, from the oldest to the yongest or vice versa, are not presented here as these have been dealt in Chapter 3, under the section 3.2.1, of stratigraphy of the study area. In fact, the lithologies and structural features as encountered while making a traverse along the section line are described.



5.2.1 Cross section W- E across the Caujeri Valley

The cross section started in the W in the mountain area of the Sierra de Caujeri in outcrops of recrystalized cross-bedding limestone from Yateras Formation (see section 3.2.1) (Fig 5.2.1),. The karst process is very well developed, with lapies and spheroidal weathering of the limestone (Plate1). The rocks are very gently dipping towards the S with dip angle between 6° and 12°. This Formation is affected by neotectonic verti-cal oscillatory movements and strike slip faults with NEE direction, which are clearly seen in the image interpretation. A graben where a whole block was displaced also appears and this could be established by the presence of tectonic breccia of limestone in the fieldwork (Plate 2). The surface of the Sierra de Cau-jeri mountain shows several relict of beheaded river channel, which could be made by rivers which drained formerly towards the West from the more elevated zone where the valley now exists. The “head” material slid towards the East into the valley. A sudden descent in the relief demonstrates the appearance of a big concave structure, suggesting the presence of big landslide or series of them. From observing rocks outcrops of the Maquey Formation in the nearest rivers channels, assumption can be made that they are lying under the Yateras Formation. However there are no outcrops in this cross section. From the structural interpretation of images, linea-ments were traced, which were interpreted as extensional faults, contributing to the understanding of the fundamental role that tectonic plays in these landslides (Plate 3,3a). Nevertheless a great lithological con-trol exists since the single presence of a formation like Maquey Formation, composed of highly terri-genous material, fragile, under a formation of calcareous compact permeable limestone; it facilitates the sliding of the rocks along the contact between these two formations. Following the profile line in the scarp of the landslide, it is possible to see the bedding of the Yateras lime-stone (Plate 4). The bedding can change from gently dipping to the South, through horizontal, and even some degree towards the North. This suggests the change of the original dips of the bedding. This because of the division of the area in small blocks and the uneven oscillatory upward and descending neotectonic movement of a block with regard to another. Great quantity of colluvial material composed of fragments of calcareous blocks and terrigenous matrix coming from higher elevations, which slipped in one case or fell down in others, deposited in colluvial form in the slope of the mountain can be detected. The landslide can be described as a multiple or succes-sive landslide using the styles of landslides activity. Due to this fact the colluvial deposits are following along the cross section by prolluvial deposits, which are more stable, possibly abandoned or relict of the old landslides. They are well consolidated and stable deposits characterized by small to medium limestone fragments and fine grain matrix without bedding. The Caujeri Valley has very well developed drainage, responsible for the amount of alluvial quaternary deposits inside the valley. Clay and silts with poor or no visible stratification and riverbed facies, coarse material and sands with cross stratification can be identified respectively. The component materials are



closely related to the original source, which are polymictic. In the case of clastic material the source rock are limestone, serpentinite, metavolcanite and other rocks from the mountain around. There is an evident neotectonic activity in the region. The rivers inside the valley are witnesses of the up-ward movements in the area, since they have begun to “eat away” quickly and intensively the previously deposited silts. Detail description of the sediment in the riverbed (Appendix.6) can show the different stages of sedimentation and erosion. The river has also moved from its original course; begun to ‘eat away’ the western side of the riverbed and increased deposition in the eastern side. A change exists in the size increase of the fragments transported by river, in accordance with the increase in force of the fluvial current (Plate 5). From small and rounded fragment the river changes to bring bigger and angular frag-ments. Very soft calcareous rocks that can be eroded outcrop in the channel of the river. However they outcrop because the speed of the uplift is greater than the speed of erosion. There are relicts of fires ob-served in the deposits, which are very young and caused in relatively very short historical time spans. There are mountain paths in the area that are now completely tunneled by the erosion, with gully of more than 1.5 m deep (Plate 6).

Figure 5.2.1 Cross section 1-1 W-E across the Caujeri Valley

Following along the cross section the San Luis Formation appears. It is characteristic of the deposits that form a porsion of the Paleogene sedimentary basin, which is visible in the study area. This basin is charac-terized by many authors as piggyback basin. Its deposits are very well developed and slightly deformed. Open folds with wide angle and fold axis oriented to the NW can be found. (More detail about this Formation in the second cross section NNW-SSE across the Caujeri Valley, Section 5.2.2). With a very well marked angular unconformity the conglomerates of the Cilindro Formation are deposited on the tope of San Luis Formation. The sequences of this Formation appear bedding monoclinal with an-gle of deps varying between 30 to 35 to the ESE (92 ) (Plate 7), characterized by polymictic conglomer-ate with well sorted and rounded fragments.



Following along the cross section are the metavolcanites, which form part of the Cretaceous foldbelt. They are highly deformed, and metamorphosed in conditions of high pressure and low temperature. The boundaries between San Luis Formation from from the Paleogene and Puriales complex are transgressive. The Paleogene deposits unconformably overlie the relief of a folded Prepaleogene substratum. Neverthe-less the relief was conditioned to previous tectonic movements and fracture hence it is easy to find fault in the boundaries between these units. Later forces have reactivated these faults along the metamorphic mas-sif contact. Outcrops of highly foliated phyllite schists, with very penetrative S1 foliation plane almost parallel to the bedding SS characterizes this part of the area, with dip direction of 329 and angle of 45 . The main folia-tion plane S1 and fracture foliation S2 are folded by third deformation, which developed a very gentle fold crenulation cleavage, with fold axis orientation or intersection lineation L3 with plunge of 15 →350 . In some places the fourth deformation phase is also evident which forms open fold with plunge of intersec-tion lineation L4 50 →310 . It is very common to find conjugated shear joints, and extensional normal kink band in which there is a volume decrease in the kink band, showing dextral sense of forces in the NS direction (Plate 8).



5.2.2 Cross section NNW - SSE across the Caujeri Valley

This geologic profile extends from NNW to SSE. It includes Formations, not included in the previous W-E Section (Fig.5.2.2) The cross section started in the NNW in the mountain area of the Sierra del Purial, in the outcrops of the metavolcanic Cretaceous foldbelt characterized by metatuff with fragmented oriented structure. These rocks are very well preserved remains of clinopyroxene crystals, generally rotated and others of recrystal-lized magmatic plagioclase in aggregate of epidote and prehnite, recrystallized lithoclasts. Very fine re-crystallized matrix with metamorphic association of chlorite-epidote-actinolite-sericite and albite can also be observed. In the mentioned outcrops two deformation phases that cross each other are clearly observed. Foliation plane S1 is nearly parallel to the bedding with dip direction of 320 and angle of 35 . Fracture cleavage plane S2 appears inclined at 232 with dip angel of 60 . The spatial relation between both cleavage do-mains is possible to classify as anastomosing type in this zone. Two principal fault systems were devel-oped, where fault plane 276 /60 was displaced by fault plane 102 /24 . Very pronounced dextral shear zone with dip direction of 285 /55 also affects the area. More to the South following the profile close folds (F1) related with the first deformation phase (D1) and crenulation cleavage related with the second deformation phase (D2) are registered.

Figure 5.2.2 Cross section 2 –2 NNW - SSE across the Caujeri Valley

Immediately after the metavolcanic complex appears the San Ignacio Formation in the top of the foldbelt, characterized by slope deposit type restricted to a very thin belt along the Sierra del Purial border. The San Ignacio Formation is composed of polymictic breccia with very poorly sorted rough clastic material, such as green schists, phyllite, and serpentinite, with little clay as cement. The Formation has a tectonic origin formed as result of a rapid uplifting of the metamorphic complex.



The occurrence of El Cobre formations in the area, which is in fact member of the Paleogene Volcanic Island Arc, and Charco redondo formation from back arc paleogene basin, was explained with its alloch-thonous origin, as part of thrusting structure. The volcanic rocks appear strongly fractured and sheared. Their contacts with others formations are always tectonic, with predominant tectonic breccia. It was very difficult to ascertain the different deformation phases in the volcanic sequences of El Cobre formation, due the limited number of outcrops from this formation, which were visited during the fieldwork. The Charco Redondo formation characterized by limestone was also affected by deformations. There are open folds with plunging fold axis (5 →350 and 5 →360 ), which are D3 deformation. Well developed open folds with plunging fold axis (6 →340 ) belonging to D4 deformation also appear. There are cal-careous breccia, and fault systems with NE-SW and NW-SE direction. Following the profile the Cilindro formation, the conglomerates of this formation are deposited on the top of San Luis formation. The Formation appears monoclinal dipping 50 to 60 angles to the South. The conglomerat nature of these deposits as well as its composition, being composed mainly of volcanic frag-ments, suggests the existance of tectonic conditions during their depositional period. The orientation of the fragments toward the south (dip angle of 15 to 20 ) and the presence of very big Lepidocycline suggest the source of sediments to be from the South during the Oligocene. The Cilindro Formation as well as the San Luis Formation appeared more than once along the profile due to the position of the profile line that was located from north to south for convenience. But as their devel-opment is practically the same they are only described once, in the most characteristic place. Following the profile the San Luis formation appears, below the cilindro Formation, characterized by in-terlayering of polymictic sandstone, lutite, marl, clay, clay limestone and polymictic conglomerate. At the beginning the deposition of this formation took place in deep marine water and later changed to deposits of shallow water. However during this work in the layers of this formation, vegetation remains or lignite was found which also suggests a lagoon environment. The presence of conglomerate on top of the San Luis Formation was in some place mistaken for the Cilindro Formation. In such cases the absence of big Lepidocycline in the sediments clarified the age of the conglomerate. The San Luis Formation in other parts is overlain by Maquey Formation. When in the top of the San Luis Formation appear also very fined carbonated terrigenous sequences then, in that cases is very difficult recognize its boundary with Maquey Formation. Generally the rocks of the San Luis Formation appear slightly deformed, characterized by open folds. However in some places of the coastal zone this formation appears strongly deformed and fractured (Plate 9). Because of fracture it is possible to find the rocks dipping with very steep angle, as well as fold with an axial plane dipping to the WNW (286 /10 ), calcite filled extensional fault (140 /75 ) and shear zone (270 /75 ). The brittle extensional deformation are clearly developed in the coastal area, where domino fault extensional system (160 /70 ) was formed on this formation (Plate 10). In others places combined strike and dip-slip fault with calcite on the surface (slickenside) oriented 110 with 15 , and also oriented 35 with 45 can be observed.



Continuing in south direction the Cretaceous metamorphic complex is found represented in this case by marble (Plate11). The rock is medium grained. Mineralogically it is composed of 80-90% of well oriented or aligned calcite subhedral crystal, 10% quartz, which also appear included within the calcite. As secon-dary mineral elongated tourmaline, muscovite, epidote and few plagioclases are present. The presence of muscovite and tourmaline suggest a low metamorphic grade, in greenschist facies. The calcite crystals are elongated, following the foliation in the direction of 350 (Plate 12). The marble is a good indicator of the different deformation phases in the area. It was possible to measure bedding and S1 with dip direction to the North and angle of 35 , and three lineation on its surface. Related with the second deformation phase D2 the lineation L2 (5 →272 ), with third deformation phase D3 the lineation L3 (25 →340 ) and another lineation L4 related with the fourth deformation phase D4 (20 →315 ) were measure. The relative angle between L2 and L4 in this place is almost 45 . The folds are asymmetrically inclined with the northern limb (330 ) shorter and steeper than the southern limb. This evidence suggests the sense of the second de-formation to be from the southeast to northwest. The intramontaneous coastal valley is characterized to be of tectonic origin. In this region a tectonic de-pression stretches between the mountains in the interior and a belt of coastal hill. It was controlled by up-lift and downward of the region and consequently transgressive and regressive stages, possible also by the rise and fall of the sea level. The valley is filled with quaternary alluvial sediments. These sediments ap-pear horizontal without deformation. They are good indicators of upward movements that are taking place in the area, because they started to develop an inverted reliefe, and the drainages have incised under the sediments. Characterized by sediment products of the third transgression-regression, from Pliocene to re-cent age. In the area clays, sandy clay and calcareous gravel as deposits appear. Near to the coast in the San Antonio bay zone (also in Baitiquiri) palustre deposit (can be peat or terrigenous carbonate deposits) are developed. There are well developed of mangrove in the coastal area. The belt of coastal hills, along the coast comprises of remains of limestone from Miocene deposits (Yat-eras formation that was in some works mapped as Cabo Cruz formation). In the southerner part of the hill, Late Pleistocene crossbedding Biohermic algaceous, coralineous and micritic limestone of Maya Forma-tion are developed (Plate 13, 13a), characterized to be karst and formed different level of terraces, which are dipping gently to the SE. In general the Coastal hill shows a highly distorted shape with rock falls and landslide that in some cases can develop to an overturned macro-block. In the East of the study area, there is a region with clinoforms with different types of deposits, including Imias formation (Plate14) composed of sequences of very energetic environment, interlayer of sandstone and poorly sorted conglomerate, coming from the North. These deposits with angular unconformity over-lie the San Luis lutite. They suggest the presence of the very steep slope as result of open Oriente fault in the late Miocene. Very recent marine deposit characterized by coraliferous limestone and calcareous conglomerates, sands and very coarse material, fragments from different sources such as metavolcanite, serpentinite, limestone and others is found towards the Southern extremity of the Cross section.



5.2.3 Cross section in Sierra del Puriales Complex

This cross section was oriented from the SW to the NE, following the river Sabanalamar, which facilitate the outcrops of the bedrock along the Sierra del Convento mountain. The main objective was to describe the sequences of the metavolcanite complex and their contacts with the ophiolite complex. Unfortunately due to the inaccessibility of the area, it was not possible to continue very long into the metavolcanic com-plex, a short cross section of the contact zone was checked (Fig.5.2.3). The cross section started in the San Ignacio Formation, with tectonic-slope deposit, which were explained in the previous cross section.

Figure 5.2.3 Cross section 3 – 3 SW – NE in the Puriales Complex

The ophiolite complex appears below the San Ignacio formation, in the mountain of Sierra del Convento. By geophysical data the ophiolite body has an extension below surface, toward the SW (Appendix 7). Its origin still remains a question. In general the ophiolite body is considered as a remanent of the oceanic crust after their spreading, and was thrusting over the Cretaceous volcanic complex as a consequence of tectonic forces coming from the south. The ophiolite appears highly deformed, weathered and metamor-phosed with trace of high pressure. In this place the rock was described as antigorite serpentinite with grains of magnetite. Paragenesis of this rocks are represented by hornblende, blue amphibole, garnet, mus-covite, pyroxene, quartz, albite, sphena and pumpellyte; hornblende, blue amphibole, muscovite, quartz, albite, chlorite, calcite, epidote, sphene and pumpellyte. The presence of the polymetamorphism in the serpentinite suggests that they were deformed and later on tectonically emplaced over the cretaceous com-plex. The hornblendes in the thin section always appear surrounded by glaucophane and the last one was transformed in chlorite. Extensional open fault with 258 /50 , conjugated faults with combined strike and



dip-slip displacement and fault striae on a polished surface (60 /80 and 60 /20 ) are developed, probably related with later extensional regime. Following the section, Quartz-metasilisite schist appears. Mosaics of quartz were aggregated. Abundant epidote (aproximately 25% of the whole rock), chlorite, muscovite and sphene lamella are their minera-logical composition. Foliation (320 /25 ) and fault zone (310 /60 ), highly developed asymmetric folds with the East limb were more deformed than in the West appear. There are very important contraction fault or brittle shear zone (115 /65 ), suggesting the hanging-wall coming from the SE toward the NW. The rocks are affected as well by fault system oriented almost N-S direction. In some places ductile-brittle deformation take place as well. Micro and meso folds highly deformed and fracture along the axial plane, and vergence toward the NW is evident. Some meters after, there is a very clear shear zone with orientation 040 /60 . Outcrops of highly deformed metasedimentary rock follow it, very well placed to study the morphology of the different superimposed folds (Plate15, 16). A second deformation phase with fold axis oriented NE direction was later folded by third deformation with fold axis oriented almost to the NW. The last ones are characterized by open folds that produced a shape of "egg box", which is the superimposed fold type 1 (Ramsay and Huber, 1987) (Fig. 5.2.4) This mentioned shape was found in several places of the area during the fieldwork.

Figure 5.2.4 Type 1 of four principal types of three-dimentional fold forms arising by the superposition of shear folds on pre-existing fold forms (Ramsay and Huber, 1987)

Following these sequences, very monotonous sequences of well oriented green schist (Plate 17) appear. Some remains of clinopyroxene, metamorphic aggregate of oriented

albite, quartz, clorite and actinollite; abundant epidote in grain and lensoidic aggregate are contained. These rocks appear dipping to the 60 /25 and later they change in the direction to north /30 . The rocks appear very fine grained with extensional deformation represented by quartz vein oriented 130 , fault sys-tem 280 /70 , extensional normal fault 350 /40 and very well developed horizontal dilatational systematic joints (Plate 18), joined by vertical cross-joints producing H and T intersection patterns. The older master joint has NW direction. The schist of metavolcanic complex were metamorphosed in the following mineral paragenesis: quartz, albite, chlorite, epidote, actinolite; quartz, albite, epidote, pumpellyte: quartz, albite, clorite, calcite, epi-dote, actinolite; quartz, albite, (andesine, augite), epidote, psilomelane, actinolite, chlorite.



5.3 Structural Analysis and Neotectonism

Previous tectonic works of the Eastern part of Cuba (Flores, 1998) devide the region in several tectonic zones. In the study area, there are two: Metamorphic Terrain Purial-Asuncion-Palenque and San Luis Guantanamo Basin. However this subdivision is too general for the present work, and more detailed analy-sis of the tectonic situation in the area is necessary. Based on above mentioned approach to the analysis of the structural data taken during the study, the area was subdivided into four structural domain based on the different development they had in the past. For domain subdivision structural-stratigraphic, tectonic and evolutionary criteria were used. The structural domains are Puriales-Convento, Sierra de Caujeri, Caujeri Valley and Coastal Valley (Fig.5.3.1). The Puriales-Convento is the most complex structural domain due to the influence of the important tec-tonic event: the thrusting of Ophiolite complex. It also represents the oldest tectono-stratigraphic units of foldbelt in the area. Consequently this domain had recorded all geological history. However, in this area after the metavolcanites and ophiolites, only the tectonic breccia of San Ignacio and some areas with Ma-quey formation were developed. This suggests that the block of the Puriales-Convento emerged almost throughout the geological time. It appears strongly deformed and faulted. (Fig. 5.3.3). From the thin sec-tion, (Plates 19,20) the foliation is defined by the preferred orientation of pyroxene, feldspar and calcite subhedrial crystals (in the marble). It formed frequently synquinematic porphyroclast with σ and φ types. The φ type has tails but no stair steeping. The σ type has wide mantles near the porphyroclast with two planar faces and two curved faces that define the asymmetry (Fig. 5.3.2). They were found indicating the sinistral strike-slip movement. According to the subdivision, the Sierra de Caujeri domain contains the allocthonous sequence of El Co-bre coming from the Paleogene island arc and tectonically emplaced later. This domain from on the other hand is characterized by all the formations present in the area but Quaternary. This suggests that the area was exposed to continuous transgression and regression the first one in the Latest Eocene to Oligocene, and the second in the Lower Miocene to Late Miocene. Fault system almost parallel to each other are de-veloped in this domain with main direction towards NE-SW and very few to NW-SE, the dip direction of the bedding plane of the Miocene Formations generally appear dipping gently toward the S or SE. Oscilla-tory vertical movements characterize the shape of the horst-graben block feature that is easily seen from the Caujeri Valley. (Fig. 5.3.3)



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Rose diagram for main fractures




Stereo contour diagram for main folia-tion S1 plane and bedding

Stereo contour diagram for bedding

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Figure 5.3.1 Structural domains for Study Area



The Caujeri Valley is characterized by negative relief. It is a tectonic depression. In this block the Mio-cene deposits were eroded due the intensification of erosional processes. Later the accumulation of the Quaternary colluvial, prolluvial, alluvial and deluvial deposits started. Now intensive erosional processes are occurring in this area. In spite of being covered by sediment, some of the fault products of the neotec-tonic movement can be traced inside the valley and they conserved the NE minor direction. The alluvial sediments in the valley are dipping horizontally but in some place already very gentle dipping to the North with 5 . This fact, the displacement of the riverbed from the original place, and the others described in the section 5.2.1, (Plate 21) suggests the uplift of the valley bottom. The uplift is not uniform. Instead the bot-tom of the valley slopes gently to the North. (Fig. 5.3.3) The Coastal Valley structural domain limited by the main Riedel (NE-SW) sinistral shear zone is charac-terized by tectonic control of relief. There are all sedimentary deposits which suggests this area to be ex-posed to continuous transgression and regression, the first one in the Latest Eocene to Oligocene, the sec-ond in the Lower Miocene to Late Miocene and the last one which started at Pliocene to Recent. In this domain it is possible to find highly deformed San Luis deposits. Several extension fault systems control the mass movement of the landslides. The presence of at least three terrace levels in the coastal hills illus-trates that neotectonic vertical movements are developed and push the recent sediments above sea level more than 200m. (Fig. 5.3.3)(Plate 22,23)

Figure 5.3.2 Clasification of mantled porphyroclasts. Sinistral sense of shear (Passchier and Trouw, 1996)



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Calculation Method .... Length

Class Interval ........ 10 Degrees

Length Filtering ...... Deactivated

Azimuth Filtering ..... Deactivated

Data Type ............. Bidirectional

Population ............ 317

Maximum Percentage .... 10.7 Percent

Mean Percentage ....... 5.5 Percent

Standard Deviation .... 2.68 Percent

Vector Mean ........... 92.73 Degrees

Confidence Interval ... 6.46 Degrees

R-mag ................. 0.61MLV

Projection ................. Schmidt (Equal Area)

Number of Sample Points .... 29

Mean Lineation Azimuth ..... 120.5

Mean Lineation Plunge ...... 78

Great Circle Azimuth ....... 359.1

Great Circle Plunge ........ 79.7

1st Eigenvalue ............. 0.674

2nd Eigenvalue ............. 0.185

3rd Eigenvalue ............. 0.14

LN ( E1 / E2 ) ............. 1.291

LN ( E2 / E3 ) ............. 0.277

(LN(E1/E2)] / (LN(E2/E3)) .. 4.654

Spherical variance ......... 0.199

Rbar ....................... 0.801

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LN ( E1 / E2 ) ............. 1.443

LN ( E2 / E3 ) ............. 0.921

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R-mag ................. 0.67MLV

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Figure 5.3.3 Rose diagrams of main fractures and stereo-contour diagram of bedding for differents structural domain.

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Great Circle Azimuth ....... 357


1st Eigenvalue ............. 0.865

2nd Eigenvalue ............. 0.087

3rd Eigenvalue ............. 0.048

LN ( E1 / E2 ) ............. 2.295

LN ( E2 / E3 ) ............. 0.602

(LN(E1/E2)] / (LN(E2/E3)) .. 3.814


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100

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120

130

140

150160170

180

19020

0210

220

230

240

250

260

270

280

290

300

310

320

330

340

350






Population ............ 67






R-mag ................. 0.71

MLV







1st Eigenvalue ............. 0.811

2nd Eigenvalue ............. 0.128

3rd Eigenvalue ............. 0.061

LN ( E1 / E2 ) ............. 1.85

LN ( E2 / E3 ) ............. 0.741

(LN(E1/E2)] / (LN(E2/E3)) .. 2.496


Rbar ....................... 0.8804

Puriales-Convento Do-main

Sierra de caujeri Do-main

Valley Domain

Coastal Domain

Sierra de Caujeri Domain

Sierra de Caujeri Dom(Northern part)

ain



5.3.1 Deformation phases

Four principal deformation phases are developed:

D1: Ductile deformation regime, which affected all the Cretaceous Volcanic Sedimentary Sequences, consist of very close (F1) macro folds which are almost isoclinal. Parallel to the bedding plane SS, S1 schistosity cleavage was generated. This deformation is difficult to see in the field as only cleavage remains. (Plates 24,17)

D2: Ductile-Brittle deformation regime. Ophiolite thrusting event defines D2 deformation. This strongly affects the ophiolite and metavolcanite near to the tectonic contact, with folds ranging from micro to meso fold (F2) and verging towards the NNW with fold axis oriented to the NE (75 ). Far from the contact the deformation are represented by fracture foliation (S2) plane. The F2 are characterized by fracture and shear axial plane developed to low-grade metamorphism (green schist facies). Other fracture and fault systems are related with this deformation phase, and transcurrent or Tear fault associated with

the thrusting event with NW orientation.(Plates 25,26,27) D3: Ductile-Brittle deformation regime. The D3 probably defined by emplacement of the piggyback

Paleogene basin which affects metavolcanites, ophiolite complexes and Paleogene formation like Charco Redondo, El Cobre and San Luis. This deformation almost perpendicular form superimposed folds above the D1 and D2, and development of the egg box pattern. The F3 folds characterized by open folds with fold axis oriented to the NNW (350 ). Sinistral Shear zone is evident with direction toward 220 (Plates 28,16)

D4: Brittle-Ductile deformation regime: It is related with the transpressional sinistral movement along

the Oriente fault. It affects all the geological units, including the recent. Controls the neotectonic activity of the whole area. It is characterized by gently dipping fold (F4) with fold axis oriented to the NW, several systems of fault, dextral and sinistral (Riedel system) strike-slip faults, extensional conjugated fault and joints. The vertical oscillatory movement in the area, with develop block systems of horst and graben structures, several terraces

level in the coastal hills, inverted relief in the valley, and several system of multiple landslides in the whole area are also related with this deformation phase. (Plates 29,32,36,38).



MLVb-ax1

b-ax1

b-ax2

b-ax3

b-ax3

Projection ................. Wulff (Equal Angle)

Figure 5.3.4 Contour Stereoplot for structural features on the Puriales Complex






1st Eigenvalue ............. 0.499

2nd Eigenvalue ............. 0.325

3rd Eigenvalue ............. 0.176

LN ( E1 / E2 ) ............. 0.428

LN ( E2 / E3 ) ............. 0.616

(LN(E1/E2)] / (LN(E2/E3)) .. 0.695


Rbar ....................... 0.5505

MLV

l-fold2

l-fold3

l-fold4







1st Eigenvalue ............. 0.652

2nd Eigenvalue ............. 0.324

3rd Eigenvalue ............. 0.024

LN ( E1 / E2 ) ............. 0.699

LN ( E2 / E3 ) ............. 2.609

(LN(E1/E2)] / (LN(E2/E3)) .. 0.268


Rbar ....................... 0.3523

MLV







1st Eigenvalue ............. 0.841

2nd Eigenvalue ............. 0.119

3rd Eigenvalue ............. 0.04

LN ( E1 / E2 ) ............. 1.951

LN ( E2 / E3 ) ............. 1.098

(LN(E1/E2)] / (LN(E2/E3)) .. 1.777


Rbar ....................... 0.4723

MLV







1st Eigenvalue ............. 0.699

2nd Eigenvalue ............. 0.275

3rd Eigenvalue ............. 0.026

LN ( E1 / E2 ) ............. 0.934

LN ( E2 / E3 ) ............. 2.36

(LN(E1/E2)] / (LN(E2/E3)) .. 0.396


Rbar ....................... 0.8126

MLV







1st Eigenvalue ............. 0.854

2nd Eigenvalue ............. 0.125

3rd Eigenvalue ............. 0.021

LN ( E1 / E2 ) ............. 1.922

LN ( E2 / E3 ) ............. 1.798

(LN(E1/E2)] / (LN(E2/E3)) .. 1.069


Rbar ....................... 0.9219

MLV







1st Eigenvalue ............. 0.924

2nd Eigenvalue ............. 0.06

3rd Eigenvalue ............. 0.015

LN ( E1 / E2 ) ............. 2.73

LN ( E2 / E3 ) ............. 1.372

(LN(E1/E2)] / (LN(E2/E3)) .. 1.989


Rbar ....................... 0.9613

Axial plane of folds for dif-ferent deformation phases

S2 foliation plane

L3 - Intersection lineation of S3 plane and bedding plane



Fold axis for different defor-mation phases



5.3.2 Principal fault system

For the whole Cuba four principal fault systems are described (Fig 2.1.4). In the present study area almost the same fault system are presented. According with the detail level of the work, the main lineament sys-tems recognized during interpretation of aerial photograph, satellite images and digital elevation model show NE-SW, NW-SE, NNE-SSW, NW-SSE and some E-W orientations. (Figs. 5.3.5 and 5.3.7)

Figure 5.3.5 Main lineament extracted from image interpretation. (Principal component PC1 was used as a background)

This fault system is very well fixed with the regional strain ellipse, associated with a strike-slipe fault sys-tem or Reidel model of brittle deformation. It is ac-tive in the area from the Miocene to Recent, due to the aperture of the Cayman Ride that started the sin-istral transpressional-transtensional movement along the Oriente regional fault. It is the responsible for the neotectonic reactivation of several old faults and the

configurations of the actual relief. (Fig.5.3.7) Figure 5.3.6 Regional strain ellipse associated with a strike-slip fault system. (McKlay. 1997)

2

2

2

2

4

4

4

4

6

6

6

6

8

8

8

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350






Rotation Amount ....... 999 Degrees

Population ............ 846






R-mag ................. 0.64

The NE-SW system is the synthetic Reidel shear fault (R1). These represent the most active faults and are characterized by sinistral normal slip fault movement in the coastal zone. Several of landslides are associ-

ated with this fault direction. It is a prominent system which has displaced all the other major directions and has control over the shape of the Coastal Valley.

Figure 5.3.7 Rose diagram of the main fracture sys-tem for the study area



The direction NNW-SSE is an antithetic Reidel shear fault (R2), and is associated with the boundary of the Paleogene basin and the metavolcanite complex, suggesting the reactivation of the older system by new forces. The direction NW-SE is the antithetic (X), and also some of the older fault related with the thrust event have this orientation. This fault system is responsible for the unequal development of the SE region of the study area, where there are remains of the clinoforms of Imias formation. Developed in the direction of NNE, there are also extensional fault which has tectonic control over the scarp feature of Sierra de Caujeri towards the Caujeri Valley and the same for others place in the Coastal Valley.

5.4 Tectonic Evolution

The evolution of the region started during the Cretaceous period, with the beginning of the volcanic island arc. At that time the volcano-sedimentary rocks of the Puriales complex were formed. After Campanian, the Cretaceous volcanic arc became extinct. These rocks were deformed and S1 foliation cleavage appear. Close isoclinal folds were also developed. In the Paleocene to early Middle Eocene new volcanic arc evolved, volcanic sequences like El Cobre Formation were developed. During the evolution of back-arc basin the cretaceous volcanic rocks were thrusted by ophiolite complex. According to the observation, the sense of thrusting can be described com-ing from the SE (160 ) to NW, and it is evident because the occurrence of deformation phase with NW limb of folds steeper than the SE limb (Fig.5.4.1). Several strike-slip or tear faults that control the unequal movement of the thrusting body were generated, as well as inverse shear zone towards 320°. The metamorphism was dated within Maastrichtian to Paleocene interval (Somin and Millan 1981). How-ever the presence of epidote growth along the crenulation cleavage suggest that they are synkinematic with the secound deformation phase. The metamorphism also could be linked with the thrusting event. Due the orogenic movement in the Middle to Late Eocene a piggyback basin was developed at the top of the Cretaceous foldbelt. Sequences such as San Luis were very well developed and slightly deformed. Unit from the paleogene arc, such as El Cobre Formation was thrusted over the sediments of the basin. How-ever this thrusting can be seen only in some parts of the basin. The generation of the thrust movement from SW (230) toward the NE develops superimposed deformation at almost 70 degree from the fold axis orientation of the previous one. Thrusting plane, shear zone and fault system oriented to the NE in the some places were also detected. These facts suggest the clockwise rotation of the maximal compressive stress, which finally lie in the NE direction.



In the Miocene transpressional-transtensional tectonic movement became active along the Oriente fault. The sinistral sense of the movement generated a predominately brittle deformation phase with several sin-istral and dextral strike slip faults. Very gentle folds with fold axis dipping towards the NW deformed the previous folded planes but almost in the same direction. Several normal folds were also generated by the system with NNE-SSW direction. As a result of strike slip movement, some other deformations appeared, but their distribution are locally, retricted to the boundaries between blocks.

Eocene

Paleocene

Miocene Figure 5.4.1 Evolution Model for the study area

The described evolution is a general one for the study area and the region. To understand the real tectonic evolution of the study area however, it is important to clarify that different tectonic structural domain had developed unequally. Based on the fieldwork observations, a tectonic-stratigraphic column for the study area was made. In Fig. 5.4.2 it is possible to recognize that certain tectonic and paleogeographic condi-tions were favorable to deposit formation in some blocks, and not in others.



In the Middle to Late Eocene, the region was subdivided in two main domains: basin and consolidated foldbelt. The boundary between blocks was the NW-SE fault system. The foldbelt part was Puriales-Convento domain and Sierra the Caujeri domain was the basin. Paleogene carbonated terrigeneous depos-its were widely distributed as part of the piggyback basin, in shallow water conditions. Later on as part of the orogenic process that were still active during the Eocene, part of the deposits from Paleogene volcanic arc, (such as tuff, from El Cobre Formation) were thrusting over the San Luis carbonated terrigenous de-posits.

San Ignacio

Prepaleocene

Paleocene

Eocene

Middle

Late

Oligocene

Miocene

Late Pliocene

Recent

Coastal Domain

Sierra de Caujeri Domain

Caujeri Val-ley

Puriales-Convent

Rio Maya Imias/ Yateras Maquey

Cilindro

San Luis

Charco Redondo

El Cobre

Ophiolite Ophiolite Sierra del Purial Complex

Marine Rock Foll

o

During the lower Oligocene, the area was characterized predominatly by outcrops and wide erosion proc-ess subsequently followed by wide deposition of terrigenous conglomerate from Cilindro formation in the basin. Main contribution of sediment at that time came from the South, which is clear from composition and orientation of the clasts within deposits. In the upper part of the Oligocene the total area including the

Puriales-Convento domain was covered by transgression and was unconformably overlain by lower part of Maquey formation. In the Late Oligocene to Miocene carbonated deposit from Maquey and later Yateras formation covered the Sierra de Caujeri Domain. Figure 5.4.2 Tectonic-stratigraphic column for the study area subdivided by different structural domain With the beginning of the transpressional movement of the Oriente fault, kinematic indicators on different scales suggest the predominant sinistral movement in the area. A general uplift of the area

and detachment of the south territory (Hispaniola Island) made possible to change the sources of the sediments, that since the Miocene started to come from the North. The whole area was affected by configuration of brittle deformation. The beginning of the transtensional movement generated the extensional fault system that controls the development of the structural tectonic depression resulting in intramontainous valleys. The Sierra de Caujeri domain was then subdivided in Caujeri Valley domain and Coastal Valley domain by faults.



The Caujeri Valley domain was destroyed by erosion caused first by uplift and then downward movement generated by vertical oscillatory movement of the tectonic block. During the first period, the upper Oligo-cene and Miocene sediments were eroded. Inside the valley, as a result of extensional regime and neotec-tonic movement, sequences of landslides following the NNE normal fault system were developed. Sub-stantial amount of Quaternary sediments was deposited in the valley. However the neotectonic activity in the valley is still present. Some of the previous deposited Quaternary sediments are now being eroded due to the general uplift of the area.

Figure 5.4.3 Tectonic stratigraphic map of the area



The Coastal Valley domain is characterized by a tectonic depression which stretches between the moun-tains in the interior and a belt of coastal hill. Historical development of the intramontain coastal valley, controlled by fault system with NE-SW and NNE-SSW direction, suggest the basin to be initially tectonic and secondly modelled by erosion. After deposition of the Quaternary (Late Pleistocene) limestone, the region was subjected to uplift, as shown by various terraces along the coast. The coastal hill belt is repre-sented by horst step block system, oscillated monoclinal limestones. Some faults related with the thrusting processes were reactivated in the last period but with different sense. The NW-SE oriented fault was tear fault with sinistral displacement, clearly observed from geophysical data. This fault displaces the ophiolite body in depth. During the reactivation of the recent neotectonic movements, the same fault developed a dextral sense, demonstrated by the subdivision in blocks of the coastal hill belt and its consequently dextral displacement.

Figure 5.4.4 Blockdiagram of structural interpretation (see also appendix 4)


CHAPTER 6 CONCLUSIONS AND RECOMMENDATIONS

Chapter 6: Conclusions and Recommen-dations

6.1 Conclusions

The present research work on geological and structural characterisation of the San Antonio del Sur area, Cuba, using data integration techniques involved literature study, remote sensing data processing and analysis, field data acquisition, processing and analysis and integrated interpretation of all observations and analysis results. As an outcome of these efforts the author has reached some conclusions which can be considered under two categories (1) general conclusions on the effectiveness of the remote sensing tech-niques and method used for geological studies; (2) specific conclusions on the geological and structural characteristics of the study area.

6.1.1 Conclusions on effectiveness of Remote Sensing techniques

• The remote sensing data for interpretation of geology and structural feature of the area was very use-

ful to identify the various formation, the lithological boundaries between formations and to interpret the major geological and structural features in the area. The synoptic coverage capability of remote sensing data proved to be particularly useful in this respect, especially for areas that had poor accessi-bility in the field.

• Digital image processing proved to be a very powerful tool for enhancing the features of interest.

Digital data integration, used for combining not only image data but also image data with attribute data, gave good results to highlight features that do not show up well on the processed single band im-ages.

• Field data capture techniques along with the data integration techniques provide an excellent tool for

updating existing geological maps and representing important information in the most optimal and ef-fective way.

6.1.2 Conclusions on the study area

Based on remote sensing data interpretation and field work observation some conclusions that were drawn on the geological and structural characteristics of the study area are listed below. The authors concluding remarks on the structural evolutionary stages of the study area follow these.



• In the study area several folds and fault systems were recognized and the whole area is characterized

into four deformational phases:

−

−

−

−

First deformation (D1): Consist of very close (F1) macro folds which are almost isoclinal. Here parallel to the bedding plane SS, S1 schistosity cleavage was generated. It affects all the Creta-ceous Volcano-Sedimentary Sequences.

Second deformation (D2): Consist of folds from micro to meso fold (F2) with vergence towards NNW, fold axis oriented to the NE (75 ). Far from the contact, the deformation are represented by fracture foliation (S2). The F2 are characterized by fracture and shear axial plane, which affected all the Cretaceous volcano-sedimentary sequences. Shear zone systems and transcurrent or Tear faults are associated with the thrusting event with orientation towards NW.

Third deformation (D3): This deformation almost perpendicular form superimposed folds above the D1 and D2, and development of the egg box pattern. The F3 folds is characterized by open folds with fold axis oriented to the NNW (350 ), and affects the metavolcanites and ophiolite complexes and also Paleogene Formations like Charco Redondo, El Cobre and San Luis. Sinistral Shear zone with direction 220 is developed.

Fourth deformation (D4): It is characterized by gently dipping fold (F4) with fold axis oriented to the NW, several system of fault, strike-slip fault, extensional conjugated fault and joints. It affects all the geological units, and forms vertical oscillatory movement developed into a system of block horst and graben. Several terrace levels in the coastal hilly, inverted relief in the valley, and sev-eral system of multiple landslides in the whole area are also related with this deformation phase.

• Analysis of data collected in the field such as axial plane, fold axis, shear zone and the study of the

contour diagram related with the second deformation phase suggest the ophiolite complex to be thrust-ing the metavolcanic complex with orientation of the main force toward the NW. The folds are asym-metrically inclined, wich the northern fold limb (330 ) shorter and steeper than the south one.

• The accommodation of the Paleogene volcanic arc, and thrusting of some part of them over the piggy-

back sediments basin was generated by main forces oriented close to the NE (according to their rela-tion with the previous deformation, which was superimposed almost perpendicular to each other). The volcanic rocks appear strongly fractured and their contacts are always tectonics, with predominantly tectonic breccia, and shear zone in the bottom plane of the formation.

• By means of the analysis of oriented thin section it was possible to establish deformation crenulation

cleavage with orientation NW and NE.


CHAPTER 6. CONCLUSIONS AND RECOMENDATIONS

• The general shape of the area and relief are controlled by the Riedel fracture of the fourth brittle de-formation phase, which was generated by sinistral transpresional-transtensional movement of the Ori-ente fault.

• The area is subdivided in to four structural domains. For domain subdivision structural-stratigraphic,

tectonic and evolutionary criteria were used. The structural domains are Puriales-Convento, Sierra de Caujeri, Caujeri Valley and Coastal Valley:

−

−

−

−

−

−

The Puriales-Convento is the most complex structural domain, due the influence of the important tectonic event: the thrusting of Ophiolite complex.

The Sierra de Caujeri domain contains the allocthonous sequences of El Cobre and Charco Redondo, coming from the Paleogene island arc and was lated tectonically emplaced. This domain on the other hand is characterized by the presence of all formation except Quaternary

The Caujeri Valley is characterized by negative relief. It is a tectonic depression where the Mio-cene deposits were eroded due the intensification of erosional processes. Later the accumulation of the Quaternary colluvial, alluvial and deluvial deposits started. This was followed by another an intensive erosional process that is continuing even in the present time.

The Coastal Valley structural domain is limited by the main Riedel sinistral shear zone. The relief of basin is controlled by initially tectonic movements that were later remodelled by erosional processes.

• From the structural interpretation of images the lineaments were traced, which were interpreted as ex-

tensional faults and are related with the presence of landslide in the area. These point towards the un-derstanding of the fundamental role that the tectonics play in the occurrence of the landslides in the area. However in the occurrence of landslides, a great lithological control exists. This is clear, for ex-ample where the presence of a Formation like Maquey, composed of fragile terrigenous material exists under a formation of calcareous compact permeable limestone this facilitates the sliding of the rocks along the contact between these two formations.

• The region of the present study is characterized by neotectonic instability:

The rivers within the valley are witnesses of the upward movements in the area since they have begun to quikly and intensively eat away the previous deposited Quaternary silts.

The surface of the Sierra de Caujeri mountain shows several srelict of beheaded river channels, which could be made by rivers which drained formerly toward the West from the more elevated



zone that was located where now the valley is. The “head” material has slid towards the East into the valley.

−

−

The apparent bedding of Miocene sediments in the Sierra de Caujeri suggests the change of the original dips of the bedding. This because of the division of the area in small blocks and the un-even oscillatory upward and descending neotectonic movement of a block with regard to another.

After deposition of the Quaternary (Late Pleistocene) limestone, the region has been uplifted, as is shown by various terraces along the coast.

• The basement of the Caujeri Valley is formed by slightly folded sediments of San Luis formation, as

in other part of the Guantanamo Basin. But in these research was not mapped this Formation inside the valley. Only Quaternary deposits, which are a result of loose material and rock fragments that have rolled down from the surrounding mountain could be seen in the Valley.

• Paleogene deposits unconformably overly the relief of a folded substratum. The relief was conditioned

to previous tectonic movements and fracture, thus it is easy to find the fault in the boundaries between these units. Later efforts have reactivated these faults along the metamorphic massif contact.

• The orientation of the fragments within Cilindro Formation towards South and the presence of very

large Lepidocycline suggest that the source of the sediments came from the South in the Oligocene • The clinoforms of the Imias Formation, developed in the SW part of the area, suggest the presence of

very steep slope as result of openingof the Oriente fault in the late Miocene. • The four evolutional stages of the San Antonio del Sur area are the following:

First: Cretaceous period marked by the beginning of the volcanic island arc. At that time the volcano-sedimentary rocks of the Puriales Complex were formed. After Campanian, the Cretaceous vol-canic arc became extinct, and these rocks were deformed with first deformation phase (D1).

Second: Paleocene to early Middle Eocene. The cretaceous volcanic rocks were thrusted by ophiolite complex. According to the observation, the sense of thrusting can be described coming from the SE to NW. The second deformation phase (D2) occurred.at this time.

Third: Middle to Late Eocene. Unit from the Paleogene island arc such as El Cobre Formation was formed. This unit was thrusted over the sediments of the basin in some places. The generation of the thrust movement from SW toward the NE gave rise to the third deformation phase (D3).

Fourth: Miocene. Transpressional-transtensional tectonic movement became active along the Oriente fault, The sinistral sense of the movement generated the fourth, predominately brittle, deforma-tion phase (D4)


CHAPTER 6. CONCLUSIONS AND RECOMENDATIONS

6.2 Recommendations

The conclusions presented in section 6.1 are based on the observations made during the fieldwork. How-ever, the complex geology of the area requires further research and investigation. Such efforts should made in the following directions: • Seeing the advantages of remote sensing data, more efforts should be directed to using advanced digi-

tal images processing techniques for enhancing remote sensing data, to extort the features of interest. New remote sensing data from other satellite platforms could be tried.

• Fusion of digital data from satellite and airborne campaigns could be tried to use the spectral capabili-

ties of the satellite data and spatial resolution of aerial photos. • Longer field campaigns should be carried out to validate the results of remote sensing data interpreta-

tion. • The area has several geological units described in previous works that were generalized. This research

takes into consideration the photogeological characteristics, stratigraphic position and fieldwork ob-servation. However, it is necessary to carry out some paleontological determination in order to con-firm these criteria.

• It will be very useful to carry out more detail microstructural and microtectonic study in the area, in

order to compare the deformation phases within the Ophiolite and Metavolcanite. • It is necessary to carry out studies, which take in consideration the metamorphic grade of the Metavol-

canic and Ophiollite complex, in order to clarify the relation of the metamorphism with the thrusting event and different deformation phases.

• Use of remote sensing and data integration techniques should be promoted within geological and field

organisations, especially in countries such as Cuba where the use of these advanced techniques by the traditional geological community is rather limited.



References and Consulted Bibliography

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provincias de la Habana. En: Contribucion a la geologia de las provincias de la Habana y Ciudad de La Habana. Editorial Cientifico tecnica, la Habana: 87-93

Andó J., M. Kozak, I. Kubovies, G. Szakmany, 1989. Nuevas formaciones metamorficas en la parte NO de Oriente (Cuba): Resumenes, Programa, Primer Congreso Cubano de Geologia, p. 111

Arriaza G. y Prol J. L., 1994. Modelo de la corteza terrestre para la región oriental de Cuba. Archivo ENG-CUPET, La Habana

Australian Institute of Geoscientists (AIG) ; Key Centre for Strategic Mineral Deposits, University of Western Australia (UWA), 1992. Geological applications of geographic information systems GIS : papers presented at a joint AIG - UWA Key centre seminar, Perth, 6-7 July 1992. - North Sydney : 1992. - 136 p. ; 30 cm. - Special issue of: AIG Bulletin 12 (1992).

Bartok, P. E., 1993. Prebreakup geology of the Gulf of Mexico-Caribbean: Its relations to Triassic and Jurasic rift systems of the region. Tectonics 12(2):441-459.

Bartok, P.E., O. Renz & G.E.G. Westerman, 1985. The Siquisique ophiolites, Northern Lara State, Venezuela. A discussion on their Middle Jurassic ammonites and tectonic implications. GSA Bull. 96:1050-1055.

Blanco, J. y J. Proenza, 1994. Terrenos tectono-estratigráficos en Cuba oriental. Rev. Minería y Geolo-gía, XI (3): 11-17

Boiteau, A., and Michard, A., 1974. Donnes nouvelles sur le socle metamorphique de Cuba. Problemes d'aplication de la tectonique del plaques (New data on the metamorphic cycle of Cuba. Problems of application to plate tectonics), Memoir VII Caribbean Geological Conference, Guadalupe, ? Caribbean, Cuba, metamorphic, kinematic, French

Boiteau, A., Butterlin, J., Michard, A., and Saliot, P., 1972. Le complexe ophiolitique du Purial (Oriente, Cuba) et son metamorphisme de haute pression: problemes de datacion et de correlation (The ophiolitic complex of Purial (Oriente, Cuba) and high pressure metamorphic: Problems of dating and correlation), Comptes Rendus Academie Sciences Paris, Series D, 275:895. Caribbean, Cuba, metamorphic, ophiolite, age, French

Boiteau, A., Michard, A., and Saliot, P., 1972. Metamorphisme de haute pression dans le complexe ophiolitique du Purial (Oriente, Cuba) (High pressure metamorphic within the ophiolitic complex of Purial (Oriente, Cuba)), Comptes Rendus de l'Academie des Sciences, Paris, 274:2137-2140. Caribbean, Cuba, metamorphic, ophiolite, French

Bovenko, V.G., B.B. Scherbakova y G. Hernández, 1980. Nuevos datos sobre la estructura geológica de Cuba Oriental (en Ruso). Sovietskaya Geologiya, No. 9: 101-109

Brezsnyánszky, K. y M. Iturralde-Vinent, 1978. Paleogeografía del Paleógeno de Cuba oriental. Geo-logie en Mjinbouw, 57(2): 123-133

Bush, W.A. e I. Sherbacova, 1986. Nuevos datos sobre la tectonica profunda de Cuba (en ruso traduci-do al ingles). Geotectonics, (3):24-43.


REFERENCES AND CONSULTED BIBLIOGRAPHY

Calais, E. (1990): Relaciones cinemático-deformantes a lo largo de los límites de las placas transfor-mantes. Ejemplo del límite de la placa norte del Caribe desde Cuba hasta Puerto Rico. Tesis de Doctorado de la Univ. de Niza. Sophia. Andepolis. Francia. 295p.

Calais, E. y B. Mercier de Lepinay 1991. From transtension to transpression all the northern Caribbean plate boundry off Cuba: implications for the recent motion of the Caribbean Plate. Tectonophysics, 186: 329-350

Calais, E. y B. Mercier de Lepinay. 1995. Strike-Slip Tectonic Processes in the Northern Caribbean Between Cuba and Hispaniola (Windward Passage) In: Marine geophysical researches : an inter-national journal for the study of the earth beneath the sea, Vol. 17 (Issue 1), 5: 63-96.

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Plates

Plate 1. Weathering limestone in Yateras Formation, Sierra de Caujeri.

Plate 2. Tectonic breccia in carbonated sequences of Yateras Formation. Sierra de Caujeri.

Plate 3. Outcrops where Yateras Formation in the top overlies the sediments of Maquey Forma-tion. Normal fault oriented to the SSE.

Plate 3a. Very big Lepidocycline characterized the Upper Oligocene age of the Maquey Forma-tion.

Plate 4. View of the scarp of a landslide in the Caujeri Valley, showing the gently bedding lime-stone of Yateras formation.

Plate 5. Riverbed, showing different stages in the sedimentation of the deposits in the valley (see also appendix 6). A change exists in the size increase of the fragments transported by river, in accordance with the increase in force of the fluvial current.

Plate 6. Mountain paths in the area that are in present time completely tunneled by the erosion, with gully of more than 1.5 m deep. Showing the faster uplift of the area.

Plate 7. Outcrop of the Cilindro Formation. The conglomerate sequences of this Formation ap-pear bedding monoclinal with angle of dips varying between 30 to 35 to the ESE. (a) shows the orientation od the fragments, (b) shows the poor sorted composition of the fragments and the calcareous matrix.

Plate 8. Extensional normal kink band in which there is a volume decreases in the kink band in the outcrop of metavolcanites.

Plate 9. In some places of the coastal zone the san Luis Formation appears strongly deformed and fractured.

Plate 10. The brittle extensional deformation is clearly developed in the coastal area, where dom-ino fault extensional system was formed. Outcrop of San Luis Formation.

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5 2

3 3a

6

1

4 7

7a 8

7b

10 9

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Plate 11. Marble from the Puriales complex outcrop. It is an example of macro fold from the second deformation phase, axial plane dipping to the NW.

Plate 12. From the thin section is clear that the calcite crystals in the marble are elongated, fol-lowing the foliation in the direction of 350 .

Plate 13. Outcrop of biohermic algaceous, coralineous and micritic limestone of Maya Forma-tion. (a) Shows an inverted coral in an overturned macro-block from a highly distorted block in the Coastal hill belt.

Plate 14. Outcrop of Imias Formation in the eastern part of the study area. The clinoforms char-acterized this Formation, with different types of deposits, composed of sequences of very energetic environment, interlayer of sandstone and poorly sorted conglomerate. These de-posits suggest the presence of the very steep slope as result of open Oriente fault in the late Miocene.

Plate 15. Outcrops of highly deformed metasedimentary rock, showing the shape of different superimposed deformation phases. A second deformation phase with fold axis oriented NE direction was later folded by third deformation with fold axis oriented almost to the NW.

Plate 16. The third and fourth deformation are characterized by open folds that produced a shape of "egg box", which is the superimposed fold type 1 (Ramsay and Huber, 1987).

Plate 17. A monotonous sequences of green schist. Plate 18. An outcrop of metasedimentary sequences of Puriales complex where are well devel-

oped horizontal dilatational systematic joints, joined by vertical cross-joints producing H and T intersection patterns.

Plate 19. From the thin section, the foliation is defined by the preferred orientation of pyroxene and feldspar. Creanulation cleavage S2 developed on S1 foliation, and S2 foliation was refolded by third deformation.

Plate 20. From the thin section the sense of the main forces during second deformation was de-fined, the plagioclase porphyroclast showing sinistral sense of the movement.

Plate 21. The alluvial sediments in the valley are dipping horizontally but in some place already very gentle dipping to the North with 5 .

Plate 23. Rock fall in the Coastal hill belt showing the intensive uplift and neotectonic move-ments.

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11 12

13a 14

14

13

15 16 17

21

19 20

18 23


Plate 22. The presence of at least three terrace levels in the coastal hills illustrates that neotec-tonic vertical movements are developed and push the recent sediments above sea level more than 200m.

Plate 24. Very close (F1) folds which are almost isoclinal. Parallel to the bedding plane SS, S1 schistosity cleavage was generated.

Plate 25. F2 folds ranging from micro to meso fold and verging towards the NNW with fold axis oriented to the NE.

Plate 26. The F2 are characterized by fracture and shear axial plane.

Plate 27. Crenulated fold from second deformation phase.

Plate 28. The F3 folds characterized by open folds with fold axis oriented to the NNW

Plate 29. Between layers of the metasedimentary rocks of Puriales complex can be observed cut-ting quartz veins, showing the discontinuous desplacement between the sandstone layers, associated with the fourth deformation phase.

Plate 30. Deformation phases in the metasedimentary outcrop

Plate 31. Foliation plane S1 in the less competent layer of schist within the marble from Puriales Complex.

Plate 32. Britle deformation from fourth deformation phase in the carbonated sediments of Ma-quey formation

Plate 33.Deformation layers of San Luis formation showing fourth deformation phase

Plate 34. Shear zone from second deformation phase

Plate 35. In the outcrop of san Luis formation deformation phases in two direction, belowing to the third and fourth deformation phases

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35

26 28

29

34

32

33

25 31

27

22 24 30

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APPENDICES

Appendices

Apendix 1 Updated Geological map of the Study Area

Apendix 1a General Legend of geological map and cross sections.

Apendix 2 Tectonic-stratigraphic map

Apendix 3 Main structural data from field observations

Apendix 4 Structural interpretation of the area

Apendix 5 Locations visited during the fieldwork

Apendix 6. Cross section on the rivers within the Caujeri Valley

Apendix 7. Magnetic data and Radar image with tectonic interpretation

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APPENDICES

Appendix 1. Updated Geological map of the Study Area

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APPENDICES

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APPENDICES

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Apendix 2 Tectonic-stratigraphic map

APPENDICES

Appendix 3. Main structural data from field observations

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Trace of folds Anticline fold axis Syncline fold axis Cleavage Thrust fault

Strike slip fault Normal fault Horizontal bedding

160

000

Appendix 4. Structural interpretation of the area

720 000700 000

170

000

Prepaleocene

Miocene

Quaternary

Paleogene

Paleogene

Miocene Paleogene

Prepaleo-cene

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APPENDICES

Appendix 5. Locations visited during the fieldwork

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APPENDICES

Appendix 6: Cross section on the rivers within the Caujeri Val-

Conglomerate

Soil and Wood roots

Coal layer

Isolate blocks

0

40

80

120

140

cm

Conglomerate

Gravel - conglomer

Sand - clay

Clay

Soil and Wood roots

ate

0

40

80

120

140

cm

The lower part of the section is represented by a sequence of conglomerate, gravel and sand, irregular cyclic bedded, showing a periodically changes in flow power of the river. In the upper half the clay accumulation predominately, that is suggesting a lost of river power, may be for long time. Now days the river is increasing the erosion potential, as is pointed by its continuos dipping and widening. Note boulders on the river flour. This fact is related with the elevation of the region. In this point the river is eroding very fast the soil layer, related with it power and the flow direction. The boulders on the river flour are showing the energetic erosion rate of the river

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APPENDICES

Appendix 7. Magnetic data and Radar image with tectonic interpretation

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geology and structural characteristics of the san antonio ... tesis-geology and... · remote...

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