Tectono-Sedimentary evolution and geochronology of the Middle Miocene Altınapa Basin, and implications for the Late Cenozoic uplift history of the Taurides, southern Turkey

Abstract

The Tauride range in southern Turkey is flanked and overlain by Neogene sedimentary basins. To the south and on top of the high range, these basins are mainly marine, whereas poorly studied intramontane basins dominated by continental deposits are exposed to the north. In this paper, we study the stratigraphy and structure of the continental Altınapa Basin, and provide 40Ar/39Ar geochronology for volcanic deposits in the stratigraphy. The stratigraphy can be subdivided into a Lower Group, displaying ~400m of fining upward fluvio-lacustrine sediments, unconformably overlain by an Upper Group with ~500m of lacustrine deposits, andesitic lavas and volcaniclastic sediments. 40Ar/39Ar dating of three volcaniclastic samples across the Upper Group provide 11.8–11.6Ma ages. The Altınapa Basin is an extensional basin, which formed predominantly due to N–S to NE–SW directed stretching. The main basin forming phase occurred during deposition of the Lower Group, prior to 11.8Ma. Paleostress inversion analyses demonstrate uniaxial stress, with highly variable extension directions that are consistent with currently observed seismicity patterns. The Middle Miocene extension history of the Altınapa Basin is consistent with a regional pattern of Middle Miocene NE–SW to NW–SE extension north of the Cyprus subduction zone. This suggests that the Cyprus subduction zone has been in retreat relative to central Anatolia since at least Middle Miocene time. The continental Altınapa Basin is currently at an elevation of ~1km, whereas partly contemporaneous marine sediments in the Mut Basin that lies on top of the Tauride range are elevated to 2km. This shows strong late Cenozoic differential uplift in southern Turkey, with at least 1km more uplift of the Tauride range than of the intramontane basins to the north. We conclude that the current high elevation of the Taurides is related to late Neogene extension and does not result from the late Cretaceous to perhaps Oligocene folding and thrusting that deformed the rocks in the range.