Mechanical significance of structural patterns identified by remote sensing studies: a multiscale analysis of tectonic structures in Crimea

摘要

Based on remote sensing analyses of two panchromatic Spot scenes that cover the western and eastern parts of Crimea, completed with the study of Landsat Thematic Mapper scenes and local aerial photographs, we determined the geometry of major structures (folds and fractures). The strikes of large fractures are quite homogeneous in the studied area: three important sets are common, N10, NE-SW and NW-SE. Two strikes are particularly developed in the western part of Crimea: N25 and N105. Along important faults, we recognised the sense of motion, which often corresponds to the latest or to the major stages of movement. We also determined stress tensors by inversion of microtectonic data sets collected in the field. Combining remote sensing analysis with mechanical studies provides new views on the structural evolution of Crimea. We thus characterised major tectonic events responsible for most of the deformation. In eastern Crimea, the structural patterns fit well with two major tectonic events. (1) The latest one is a Plio-Quaternary faulting event (normal slip along N10 faults and strike-slip motion along N10 and NW-SE faults) corresponding to a transtensional regime, with#sigma#_3 trending E-W. (2) Large fractures (NW-SE and NE-SW sets) and fold-and-thrust development reveal a transpressional regime, with #sigma#_1 trending NNE-SSW during the Berriasian. In western Crimea, we characterised a more complex pattern of four major tectonic events. (1) The Plio-Quaternary tectonic phase induced left-lateral displacement along NW-SE faults and normal slip along WSW-ENE faults and this deformation is in agreement with the strike-slip regime that we reconstructed with #sigma#_3 trending NNE-SSW. (2) As for eastern Crimea, the Berriasian phase was well expressed, with folds, thrusts and strike-slip faults, under a transpressional regime with #sigma#_1 trending N-S to NNW-SSE. The two other events well identified in western Crimea are: (3) a N-S-directed extension that developed large N105 faults, and (4) a NW-SE-directed extension (involving NE-SW normal faults) that we relate to the development of peripheral troughs in the Oligocene. Western Crimea suffered a more complicated structural evolution than eastern Crimea. From eastern to western Crimea, we also noticed the systematic deviation in the trends of the principal stress axes of the recent stress field and in the Berriasian stress field as well. These differences may be related to the presence of a major crustal discontinuity: the transverse Alushta-Simferopol fault.