Fault tectonics of the Tuscan Nappe in the eastern sector of the Apuan Alps (Italy)

Abstract

We present the geological-structural map of the Tuscan Nappe exposed on the eastern border of the Apuan Alps metamorphic dome (Tuscany, Italy). The 1:6,500 scaled Main Map covers an area of about 10 km2. It contains the first detailed overview of the fault tectonics affecting the Tuscan Nappe during the exhumation and uplift of the Tuscan Metamorphic Units. We documented a polyphase fault tectonics that initially produced low-angle extensional faults and later high-angle faults. The latter started within a transtensional tectonic regime that produced left-lateral strike-slip faults. Lately a pure extensional tensor, indicating a switch of the maximum compression σ1 axis from sub-horizontal to sub-vertical, produced faults with a dominant dip-slip component. In our reconstruction the lateral thickness variations documented in several formations of the Tuscan Nappe is mainly controlled by tectonics and not by stratigraphy, as previously suggested.