Tectonic evolution of the western Catanzaro Trough (Calabria, South Italy), preliminary results

F. Brutto 1, F. Muto 1, M.F. Loreto2, V. Tripodi 1, S. Critelli1

1 Dipartimento di Biologia, Ecologia e Scienze della Terra (DiBEST)- Università della Calabria, Arcavacata di Rende (CS), Italy 2 Istituto di Scienze Marine – Consiglio Nazionale delle Ricerche, U.O.S. Bologna, Italy

Structural features of Catanzaro Trough

The study area is located in the western sector of Catanzaro Trough (central Calabria), extending from the Sila Massif, on the South, to the Serre Massif, on the North (Fig.1). The aim of this work is to define the Plio-Quaternary evolution of central Calabrian Arc. The preliminary structural and geophysical data analysis allow us to identify two main fault patterns: 1) the WNW-ESE oriented system has controlled the opening of Catanzaro Trough during the Middle Miocene; 2) the NE-SW oriented fault system which produce an overall WNW-ESE extension, likely due to the development of the Tyrrhenian Rift Zone. The structural framework of the Calabrian belt is further complicated by the re-activation of these oriented fault systems, time after time, with different kinematics.

*Corresponding author. Email: fabrizio.brutto@gmail.com

The CT (Catanzaro Trough) is bounded by different fault sets influencing its morpho-tectonic evolution. The preliminary structural results, coming from structural data and seismic lines interpretation allow us to identify several tectonic phases that have characterized the study area since Middle Miocene. Assuming a constant seismic velocity of 2200 m/s for Plio-Quaternary sediments, we can estimate discontinuities exsisting within the Plio-Quaternary sedimentary sequence of the ViDEPI profiles (Fig. 3).

Abstract

Fig.1 Geological map of the study area

These Major Faults show different kinematics phases: •Extensional Phase (Middle Miocene) •Compressional/transpressional phase (late Miocene -Pliocene) •Extensional /locally transcurrent phase (Pliocene-middle Pleistocene), •Extensional phase (late Pleistocene) The first two phases are mainly related to the WNW-ESE faults system, even though locally they show transtensional kinematics. The latter have been related to the NE-SW and NNE-SSW faults system, outcropping along the northwestern and southwestern margins of Catanzaro Trough. By agreement with the latter faults system, in the offshore Tyrrhenian area, the S. Eufemia Fault activity has been described, this NE-SW oriented normal fault offsets the Holocene sedimentary cover (Loreto et al., 2013) contributing to the deepening of the sedimentary basin (Fig.8). In conclusion: the WNW-ESE oriented faults are responsible for opening of a NW–SE palaeostrait that connected the Tyrrhenian area to the Ionian Sea during multiphase tectonics until early Pleistocene. While NE-SW and NNE-SSW fault systems border and control a Late Quaternary Catanzaro Trough Sub-Basin, arranged as a Graben System, in response to the last extensional stages of Tyrrhenian back-arc basin opening.

Fig.5 Above. Compressional /transpressional phase: a) Transpressional fault within the Messinian conglomerates; b) evidence of compressional phase in SE-5 VIDEPI seismic profile (blue square), the seismic profile shows a Messinian-confined thrusting

Fig. 6 On the right, Extensional/ locally transcurrent phase: a) Pliocene conglomerates desplaced by several NE-striking normal faults; b) the CZ-329-78 ViDEPI seismic profile showing a normal fault (blue square) that offsets Late Miocene- Pliocene layers

a

Fig.7 On the right, Extensional Phase: a) Faults offsetting the Middle Pleistocene marine terraces; b) CZ-377-87 ViDEPI seismic profile displays at least three faults that offset shallow layers (blue square)

Fig.4 Above. Extensional phase: low-dip angle normal fault: Sila Unit metagabbros and gneiss.

Fig. 3: On the right. Structural map of study area, we have defined some mesoscopic fault patterns: a) WNW-ESE oriented faults system with normal and oblique kinematics bounding to the north the CT, whereas the NE-SW oriented faults showing normal and right oblique kinematics outcropping to the northwestern edge; b) N-S and NNE-SSW oriented faults system, south of CT showing normal and oblique kinematics and describing a new extensional tectonic phase, likely active during the Pleistocene and producing a further deepening of the basin.

Fig.8 The Catanzaro Through Sub-Basin arranged as a Graben System, bordered by antithetic faults, represented by the S. Eufemia Fault, to the NW, and the prosecution of the Vibo Valentia Fault in the CT, to the SE. The last, supposedly, was displaced by the Curinga fault systems. More details in Brutto et al. 2014.

References BRUTTO F. et al., 2014. New features about the Catanzaro Through evolution (Calabria, South Italy) by joining onshore with offshore data. Rend. Online Soc. Geol. It., Suppl. n. 1 al Vol. 31

LORETO M.F., et al., 2013. Approaching the potential seismogenic source of the 8 September 1905 earthquake: New geophysical, geological and biochemical data from the S. Eufemia Gulf (S Italy). Mar. Geol. 343, 62–75. TANSI, C., et al., 2007. Neogene–Quaternary strike-slip tectonics in the central Calabrian Arc (Southern Italy). J. of Geodyn., 43, 397–414.

Acnowledgements This research is part of Fabrizio Brutto’s PhD research ‘Geological-structural evolution of active tectonic areas in the central Calabria‘, this work is still in progress. The PhD project is carried out within PhD Programmes “Archimede” in Sciences, Communication and Technologies, cycle XXVIII at University of Calabria. We wish to thank CNR-ISMAR (Istituto di Scienze Marine) and OGS Institute for permission to consult seismic reflection profiles carried out in the S. Eufemia Plain and to publish its line drawings.

The structural complexity is strictly related with the highest probability of occurrence of major earthquakes in the Mediterranean region. The distribution of crustal seismicity shows that most of the events which have occurred in the study area are located in the hanging-wall of Plio-Pleistocene normal faults, the largest of which reached magnitude, instrumentally estimates, in a range of 6<M<7 (as the earthquakes sequence of 1783, the 1638 and the 1905 earthquakes) (Fig. 2).

Conclusion The new geo-structural data allowed us to provide further insights on the Neogene-Quaternary “Catanzaro Trough” evolution. The development of this basin has been intensely influenced by two sets of Major Faults. The first of these, the WNW-ESE oriented faults system, borders the northern (Lamezia Terme-Catanzaro Fault; Tansi et al., 2007) and southern (Stalettì-Squillace-Maida Fault) edges of the Catanzaro Trough. The second ones are characterized by the NE-SW (Vibo Valentia faults) and the NNE-SSW (Curinga faults) oriented fault systems.

Fig.2 Epicentral location of historical earthquakes and Major Faults in the study area Fig. 2

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