Do we need the orogen-parallel dextral strike-slips during the Miocene tectonic evolution of the Western Carpathians?

摘要

The present shape of the Carpathians is a result of invasion of the Alpine orogenic system into the foreland embayment composed of subducting oceanic and/or thinned continental crust. To fill-in this realm with the Western Carpathian units by lateral extrusions of crustal blocks, sinistral shifts along generally NE-SW and/or N-S strike-slip faults are expected. Nevertheless, there are described and interpreted the orogen-parallel dextral strike-slips related to the Late Cretaceous-Early Miocene transpressional stages of tectonic evolution. To explain their origin during N-S convergence is rather complex, because it needs a large counter-clockwise block rotation after the dextral transpressional events. Herein we discuss a possibility of dextral shearing along the prominent orogen-parallel Carpathian Shear Corridor (CSC) that was active even after the ALCAPA counter-clockwise en-bloc rotation. After collision of advancing Carpathian units with the northern foreland, the CSC, already oriented ENE-WSW, started to operate as a southern dextral strike-slip boundary of the small frontal, peri-klippen crustal fragment. This block between the CSC and the Pieniny Klippen Belt (PKB), was escaping to ENE, to occupy a free area. At the same time, the NE-SW PKB zone operated as a northern sinistral strike-slip boundary of this wedge-shaped block. After the firm attachment of this peripheral crustal block with the foreland, the sinistral shearing along CSC corridor had initiated and drove the extrusion of the large Central Western Carpathians crustal segment to the ENE. It follows that the dextral shifts along the CSC are necessary. Not only to create a dextral transpressional tectonic style of the Early Miocene events, but, in next event, to extrude the small peri-klippen crustal fragment as a single block to the NE as well.