Wrench and thrust tectonics along a Mesozoic–Cenozoic continental margin: Antalya Complex, SW Turkey

Abstract

The segment of the Antalya Complex W of Antalya Bay displays the results of latest Cretaceous to Miocene deformation on a previously passive Mesozoic continental margin. The 300 km 2 area detailed here includes parts of, from W to E, a Mesozoic carbonate platform, its bordering sediment margin and the adjacent marginal oceanic crust with sediment cover. The platform is folded on N–S axes and has been overthrust westward by its sediment margin. This thin sediment sequence has been detached from its basement in a spectacular W-verging imbricate thrust belt. Similar, though less organized, westward thrusting occurs in the thin sediment cover to the marginal oceanic crust, and may also affect the igneous basement itself. However, this part of the margin is dominated by an array of anastomosing subvertical screens of serpentinite up to several kilometres wide. These are thought to be cool, upward protrusions of the hydrated ultramafic substratum to the marginal crust into a then active, braided, strike-slip fault system. The fault strands now divide the intact marginal rocks into large lozenges, some of which have oblique and sigmoidal structures and steeply plunging folds. The thrust and wrench tectonics may have operated in concert in a regionally transpressive regime, or thrusting may have accompanied only the initiation of wrench tectonics. The local interplay of transpression and transtension was partly responsible for the present complexity of the area. Even more important was the original mechanical inhomogeneity of the margin, particularly the inclusion of rifted-off continental fragments in the marginal ocean crust and the strong basement/cover contrasts on the margin.