LANDSAT Thematic Mapper Imagery Applications in Analysis of the

Structural Geological Elements from the Area of Dâmbovicioara Corridor,

Romania

MĂDĂLINA NICOLETA FRÎNCULEASA , ALEXANDRU ISTRATE Department of Geography, Faculty of Humanities

Valahia University Str. Lt. Ion Stancu, no. 34/36,130024, Târgovişte, DâmboviŃa,

ROMÂNIA madalina_chitescu@yahoo.com, alexandruistrate@yahoo.com

Abstract: - This study indicates the way Landsat TM data are used to determinate and interpret structural geological elements (lineaments) in the area of Dâmbovicioara Corridor. Remote sensing data, as well as the data provided by Landsat TM, can be used in order to locate the old geological elements shown on the already published maps and also new lineaments that cannot be found on these geological maps. The map of the structural geological elements (lineaments) and the analysis of the satellite data are a rapid, new and stimulating starting point for regional geology (the study of lineaments). Key-Words: - Dâmbovicioara Corridor, remote sensing, Landsat Thematic Mapper, thematic maps, lineaments

1 Introduction 1.1. Setting

The area of Dâmbovicioara Corridor is a region with a “distinct geographic individuality” [20]. Shaped as a parallelogram, the area under study is generally oriented NE-SW. Its width varies from 6 km at Dragoslavele to 14 km at Moeciu de Jos.

Considered to be a transitional area between the crystalline of the Meridional Carpathians and the zone of flysch of the Oriental Carpathians, the area of Dâmbovicioara Corridor has characteristic features that were determined mainly by the tectonic factor. Thus, this region displays both a relatively complicated combination of the folded structure (generally oriented from N-S to NNE-SSW) with a convergent structure overlapping in the north and a disjunctive tectonics with normal horsts and rift valleys in the entire system and with antithetic steps as a result mainly of distension forces and to a lesser degree of compression forces.

This situation is due to the intumescences of Leaota anticline, which generates all these under the action of the compressional forces, followed by the distension of the superficial parts of the branch anticline, especially of the Mesozoic layer. The fractural tectonics of Dâmbovicioara Corridor is marked by fractural events of the ground, most often transversal, oriented from NW-SE up to W-E. The majority of them were generated during two stages of

diastrophism, a post-Bedoulian and ante-Vraconian one, and the other post-Paleogene.

Fig.1 Location of the area under study and its place in the Romania.

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However, one can recognize as well fractural events generated before the Vraconian, through the thickness variations in-between the Mesozoic and the Vraconian formations (the central part of the rift valley of Podul DâmboviŃei) reactivated during the phases of post-Cretaceous diastrophism, which sometimes exaggerate the pre-Vraconian structures (the syncline of Piatra Craiului) or give birth to inversions of these forms (the rift valley of Podul DâmboviŃei generated on a pre-Vraconian mount).

The folded tectonics of Dâmbovicioara Corridor is well individualized by means of a series of anticlines and synclines (which form the dominant element, having the same orientation as the corridor, SW-NE), and also by means of other folds placed orthogonally on this direction. They are the result of the last (Cretaceous or Paleogene) folding that affected the area. Because the Neocomian and the Barremian-Aptian marls from around Dâmbovicioara belong to a syncline which is only partially expressed in the layer of the Vraconian deposits, which, on the flanks, go beyond the Neocomian deposits laying directly on the Neo-Jurassic calcareous stones, one can notice as well earlier folds, formed during the Mid-Cretaceous diastrophic phase – the austric phase [13].This system was generated before the Vraconian and certainly reactivated after the Paleogene.

2 Problem Formulation

2.1. Objectives

The objectives derived from our main purpose, that of introducing satellite images and using them on a regular basis in geology, according to the current global tendencies, as they appear more and more frequently, not only in geology but also in other domains, by comparison with the aerial images. What are the purposes of this study?

1. to show the applicability of remote sensing data in the structural geological study (to determine the liniaments who corresponding to joints or faults), taking as example Dâmbovicioara area;

2. to evaluate the images produced by means of remote sensing techniques in order to draw the map of the lineaments;

3. to prepare the structural map (of the liniaments) starting from the interpretation of the remote sensing data, comparing them to the already published regional map;

4. for drawing the future geological maps who will include new joints and faults which appear only on satellite images as lineaments.

The purpose was to determine and classify the types of fractural and folded elements on certain categories. The steps we followed were: determination

of all the linear elements; selection of the linear elements on genetic categories; achievement of rose diagrams; achievement of the element density maps based on the quantitative assessment of their appearing; determination of the types of linear elements in order to emphasize their features; outlining of the sectors characterized by major linear elements and overlapping them over the geological formations.

2.2. The methodology of data processing

and interpreted We processed the satellite images of the type

Landsat TM (Thematic Mapper) bands 4, 5, 3 – RGB, on a scale of 1:1000000. The scenes we used were 149/29 of September 23, 1992 and 150/29 of July 12, 1986. The available data were interpreted following the steps proposed by [11]. We used the information from 6 contrast bands and we interpreted them digitally. The images of all the bands were compared in terms of contrast and defined through their geological features (as lineaments).

The first step in the attempt to achieve an inventory and a classification of the structural elements from the region under analysis was to determine all the linear elements that could be highlighted starting from the spatial images. As a result of the visual evaluation, the Landsat TM band 5 data were selected for this study, because they offer a good contrast and improve the comparison between the lineaments we consider geological that are shown on this band and those from other bands.

The analogical processing of the images was achieved using the multispectral projector MSP-4C. It was chosen because it allows one to increase 5 times the scale of the materials that are used. Thus, we obtained falsely colored images on a scale of 1:200000. We used falsely colored images on this scale because they allow a comparison with the existing geological maps edited by the Romanian Geographic Institute (IGR) (Geological map, Braşov Sheet, 1:200000, 1972).

The interpretation of these images led to the achievement of a map with total linear unselected elements. At the same time, the visual interpretation on the computer display and the increase of the images to a convenient scale allowed the separation of the different types of elements. Thus, we were able to determine a number of 785 linear elements (lineaments), representing structural elements, topographic elements and man-made elements (roads, bridges, irrigation canals and electric wires).

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3 Interpretation and Results

3.1. Determination and the selection of the linear

elements on genetic categories The following step, after the completion of the

map with total linear unselected elements was to compare it to the topographic and the geological map. These comparisons/ this overlapping allowed the elimination, step by step, of the diverse genetic categories of elements. Thus, it was possible to achieve a series of thematic maps: the map of the geological elements, the map of the topographic elements and the map of the total elements.

Fascicle (F) represent group of small and medium linear elements dispose like colinear or parallel lineaments. S is orientation system refer to geographical north of the all linear elements.

The first stage of the comparison between the two types of maps led to the elimination of all the elements considered to be man-made, thus resulting the map of the total (geologic and topographic) linear elements. The result was a map with a number of 697 elements.

In the remote sensing research, the map of the total elements was the framework for the elaboration of different thematic maps considered necessary for a geological interpretation. Then we selected the topographic and the structural geological elements and the relations between them.

When approaching the studies on the achievement of a map of the structural geological elements, we started from the idea that most of the elements that appear on the map of the total linear elements had as direct or indirect trigger the tectonic activity manifested in the region. After the exclusion of the elements that we considered topographic (rivers, questas, roads, bridges, irrigation canals and electric wires), we were left with a number of 476 potentially geological elements. The elements of the map with geological elements were processed statistically and rose diagrams were constructed according to their length and frequency of appearing.

As number of elements we noted 242 elements in the eastern quadrant and 218 elements in the western quadrant. The main direction is N20oE-N60oE (150 elements) for the first, while for the second quadrant the principal direction is N20oW-N40oW (134 elements).

After obtaining the map of the elements selected for being geological in nature, we followed the same principle in order to achieve azimuthally diagrams. From the viewpoint of the number of elements, we noticed 95 elements in the eastern quadrant and 218 elements in the western quadrant. The main directions are N40oE-N60oE

(58 elements) for the first and N20oW-N60oW (62 elements) for the second.

Fig.2. Network of lineaments. L7-major lineaments; F2-segments fascicle; S3-sector.

Considering the different aspects present in the map of the total linear elements supposed to be geological-structural in nature, we established three main sectors, taking into account the distribution of the linear elements and of the petrographic areas that they characterize. -Sector 1 (in the north), limited in the south by the linear element L6 and by the fascicle F3. It lies on top of some crystalline formations and of certain Jurassic and Lower Cretaceous sedimentary patches (Cheile Prăpastiei, Zărneşti). In this sector the remote sensing data indicate the existence of a number of 31 elements, of which 20 in the eastern quadrant and 11 in the western quadrant. These elements are relatively evenly distributed in the area. They belong to the orientation systems S1, S2, S5, S6, S7, S8 and S9. The systems S2 and S7 contain the highest number of elements, respectively 13 and 6; -Sector 2 (in the center), limited in the north by L1, F2, F1 and F3 and in the south by L13, L6 and F9, F19 and F20. It is the sector with the highest density of linear elements, a phenomenon also explained by the presence in this sector of 27 of the 33 fascicles identified and outlined in the region. From a geological viewpoint, this sector is characterized mainly by sedimentary formations of Jurassic and Cretaceous age. The number of linear elements from this sector is of 139, of which 59 in the eastern quadrant, 76 in the western quadrant and 4

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southwards. These belong to all the orientation systems, mainly to S1 (14 elements), S2 (15 elements), S3 (20 elements), S6 (13 elements), S7 (23 elements) and S8 (18 elements); -Sector 3 (in the south) is limited in the north by F7, F6, F4 and L4 and in the south by L1, L11, L12 and F1. It is a sector with a low number of elements, relatively spread in the area. It lies on top of both the crystalline and the sedimentary deposits. Its number of elements is 51, being the second among the sectors from this viewpoint. The orientation systems to which these elements belong are all present except N80W-N90W. Their distribution in the orientation systems is relatively even, without important differences: S1 (4 elements), S2 (4 elements), S3 (6 elements), S4 (2 elements), S6 (9 elements), S7 (5 elements), S8 (9 elements) and S10 (7 elements).

We observe a distribution of the elements in the three sectors with a larger number in the western quadrant S1 (20 elements), S2 (35 elements) and S3 (76 elements). As we can notice, the most important from the viewpoint of the information obtained by means of remote sensing is the sector 2 (S2), from the center, characterized by the highest density of the linear elements and by the presence of the largest number of fascicles, corroborated with the existence of the obvious tectonic structures and of the petrography (calcareous, marls and conglomeratic formations).

The rose diagrams highlight the existence of orientation intervals with maximum values (S2–N40oE-N60oE, N20oW-N40oW, S1o–N20oE-N40oE, N40oW-N60oW), namely N20oE-N40oE, N40oW-N60oW, as well as of others with high values compared to the rest of the intervals. The analysis of these orientation intervals shows that both in the northwestern quadrant and in the northeastern one, the best individualized is the S2-S8 system, symmetrically comprised between 40o-60o. The intervals with maximum values from the rose diagram in point of length can coincide with those from the rose diagram in point of frequency; however this does not represent a general rule.

For a more detailed analysis of the region, beside the total diagrams and the diagrams for each sector, we achieved separate rose diagrams for the main types of geological formations, like in the other cases, according to the length and frequency of the linear elements. The comparison between the rose diagrams corresponding to the different types of geological formations, and the comparison with the total rose diagrams highlights the fact that most of the elements are located in the northwestern quadrant, both for the conglomerates and for the calcareous stones and the crystalline.

Relying on the different aspects shown by the analysis of the map with the total linear elements, on the rose diagrams and on the linear element density map, and having as a starting point the total rose diagrams, we established 10 orientation systems for the linear

elements, on the whole, and seven orientation systems for the major linear elements. At the same time 33 major linear elements were individualized, of which 9 are considered double elements. At the same time, 24 fascicles of linear elements were established as well. These fascicles are made up of linear elements and of segments of average and small dimensions, organized as more or less co-linear and parallel lineaments.

Fig.3. Map of the lineaments thought to be geological in nature. Rose diagrams by length and frequency.

The systems of orientation for all the elements were marked as “S” and counted from 1 to 10, while the major ones were marked as “Sm” and counted from 1 to 7. The linear elements were marked as “L”, counted from 1 to 33, for the double ones the letter “a” being added, while the fascicles were marked as “F” and counted from 1 to 24. The repartition of the major linear elements and of the fascicles in the seven systems is as follows: Sm1 (N1oE-N20oE) contains the linear elements L7-L11, L14-L21, and the fascicles F1, F3, F4, F5, F7; Sm2 (N20oE-N40oE) contains the linear elements L1-L3, L28-L30, and the fascicles F20-F23, F15-F17; Sm3 (N40oE-N60oE) contains the linear elements L5, L24-L26, and the fascicles F2, F8-F10; Sm4 (N20oW-N40oW) contains the linear elements L4, L13, and the fascicle F24; Sm5 (N40oW-N60oW) contains the linear elements L12, L31-L33, and the fascicles F6, F11-F13; Sm6 (N20oW-N20oE) contains the linear elements L22, L27-L30, and the fascicles F23, F8-F10, F23; Sm7 (N60oW-N80oE) contains the linear element L23, and the fascicles F14, F18-F22.

This aspect is more obvious because the rose diagrams were built based on a relatively large number

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of linear elements, presenting configurations with a number of 4-6 maximums, while the major elements well-outlined as direction do not belong to the orientation intervals with high values because they are not accompanied by a sufficiently large number of linear elements with the same orientation.

3.2. Comparative interpretation

In the area under study, we were able to determine 476 lineaments (the size of each one of them going beyond 500m), whose lengths, summed up, goes beyond 1200km. Anyway, any linement larger than 1km is highlighted on the map, as it can represent local geological fractures. The lineaments were analyzed in terms of their orientation and position in comparison with the faults marked on the already known map. They show a slight difference by comparison with the map published by IGR, motivated however by the numerous scale transformations of the images and of the maps. At the same time, these indications, based on orientation, and most of the characteristics of the model containing the faults are increased from the liniament map. In terms of size and of the total number, the lineaments that could be drawn are much more numerous than those already presented on the IGR map.

Fig.4. Comparation between faults (I.G.R. geological map (1:50.000, sheet Brasov, Zărnesti, Bran, Fundata) and liniaments.1.liniaments corresponding presented faults on the IGR map. 2. liniaments on satellitare image

The lineaments whose size goes beyond 1 km

look similar to the model containing the faults shown by

the existing map of the area. The size of the lineaments that can be drawn and the fact that they correspond very well to the faults proposed by the 1:200000 map show that the lineaments that are longer than 2.5km can be interpreted as joints without a subsequent comparison to the geological map, because they are too big to represent fissures or gaps without any fractural location along them.

Checking this interpretation on the I.G.R. geological map (1:50.000, sheet Brasov, Zărnesti, Bran, Fundata), we noted that, in the area under study, the slight differences appear as a consequence of the fact that the rock outcrops are not always available, being hidden by vegetation and subject to the meteorological conditions.

In terms of number and length, the lineaments that can be drawn are respectively 6.7% and 3.7% more numerous than in the existing maps, several differing in size from the faults in the respective maps. Some major lineaments do not coincide with the faults presented on the map and are interpreted as representing faults that have not yet been recognized as such and presented on any existing map. Anyway, they are lineaments (many of them under 1km in length) that do not coincide with the faults and are interpreted as possible small faults. Others, determined on the processed images, are also presented as circular characteristics (very few – actually only one), but the geological significance of these characteristics could not be interpreted and correlated to the data obtained in the field. The density of the lineaments in some areas of the zone under study is much higher than in the areas around them, without being very well correlated to the lithology of the respective area.

4 Conclusions A first interpretation of and discussion on the

geological structure highlighted by means of the lineaments present on the satellite images allow us to draw certain conclusions: -remote sensing techniques can be successfully used to extract structural geological information (lineaments), generally for any zone in Romania and especially for the area of Dâmbovicioara Corridor. When other types of satellite images with a higher resolution are used, the lithological and lineament analyses can be achieved in detail as well. In order to obtain certain elements, remote sensing techniques can be successfully accompanied by numerous techniques specialized on remote sensing offered by GIS. The most useful are: the analysis of the principal components, the “tasseled cap” transformation, the band ratio and the fusion of images; -the applicability of this type of study can be useful for a detailed presentation of the structural characteristic features of a future geological map;

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-the most numerous pieces of information, especially those concerning the age of the faults, were interpreted starting from the images offered by the Landsat TM. The draft obtained following the interpretation of the satellite image presents a structural-tectonic image that represents the surface prelude of the fault system that affected the area of Dâmbovicioara Corridor, highlighting the faults’ active period in the course of the formation of the basin; the structural-tectonic draft obtained based on the interpretation of the satellite images has similarities with the existing structural map. This is an argument in favor of the truthfulness of the structural map achieved and excludes to a large extent the interpreter’s subjectivity.

The results obtained by processing, analyzing and interpreting the satellite images can be applicable both in the activity of scientific research and in the activity of determining the geological features of a region. The importance of these preoccupations is totally justified taking into account the dynamics that can be observed in the evolution of certain competitive recordings that one could have hardly imagines a decade ago (the satellite images resemble the aerial images in point of their uses, but have obvious advantages from the viewpoint of their economic efficiency). References: [1] Adragna F, Interferometrie radar: principe, applications et limitations. Bulletine Francaise de Photogrammetrie et teledetection, 148, 1997, pp.17-29. [2] Akhir J M, Abdullah I, Geological Applications of LANDSAT Thematic Mapper Imagery: Mapping and Analysis of Lineaments in NW Peninsula Malaysia, AARS-ACRS, 1997, pp.121-127. [3] ChiŃescu M., Structural geological applications of Landsat Thematic Mapper imagery. Conclusion to the analysis of the structural geological elements in theareaofDambovicioara Corridor.”UNIVERSITARIA SIMPRO 2005”, 2005, pp.27-32 [4] Catardiere (de la) PH, Penot J-P, Dictionnaire de l espace. Larousse Paris, 1995. [5] Dionisă V., Dionisă I., DicŃionar explicativ de teledetecŃie şi sisteme informaŃionale geografice. Junimea, Iaşi, 1982. [6] Drăghindă I., Aerofotografia în cercetările geologice. Editura Tehnică, Bucureşti, 1966. Drury S., Image interpretation in Geology. Third edition, Nelson Thornes Ltd, UK, 2001. [7] Frînculeasa M., EvoluŃia geologică a Culoarului Dâmbovicioara, Editura Cetatea de Scaun, Târgovişte, 2010. [8] Grădinaru G., TeledetecŃia, metodă statistică în societatea informaŃională. Revista Informatică Economică, 3 (23), 2002, pp.46-51 [9] Imbroane A M, Moore D, IniŃiere în GIS şi teledetecŃie. Presa Universitară Clujană, 1999.

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