CONDITIONS AND POSSIBLE MECHANISMS OF FORMING OF LISTRIC FAULTS AND THRUST-FOLD OROGENS

Abstract

In the article is discussed the insufficiently studied problem of an origin of the listric faults widely spread in nappe-thrust folded areas. It is shown, that represented in geological cross-sections of these regions displacement of different separate nappes and tectonic sheets with different amplitudes along of typical listric faults are practically impossible because of occurrence of «space problems». It’s defined, that the difficulty is caused by formation of zones of opening or overlapping during the movement of blocks along curved surfaces of listric faults in the conditions of horizontal compression. It is assumed, that the listric form of faults is secondary and it was formed by the deformation of existed faults of various morphology. Presented kinematic features of their occurrence showing, that they are formed by two essentially different mechanisms: As a result of twisting of parts of thrusts or owing to a curvature and a flattening of lower parts of reverse faults. On this basis two genetic types of listric faults are distinguished; originating from different age disturbances of newly developed flat chopping offs and early formed abrupt faults. Experiments with the purpose of modeling of listric faults, which have confirmed the authors views on genesis of these structures are described. The conclusion is made, that listric faults within the limits of thrust-fold orogens are developed due to both mechanisms.