Late Miocene surface uplift of the southern margin of the Central Anatolian Plateau, Central Taurides, Turkey

摘要

The timing and pattern of surface uplift of Miocene marine sediments capping the southern margin of the Central Anatolian Plateau in southern Turkey provide a first-order constraint on possible mechanisms of regional uplift. Nannofossil, ostracod, and planktic foraminifera biostratigraphy of the Basyayla section (Mut-Ermenek Basin) within the Mut and Koselerli Formations suggests a Torto-nian age for marine sediments unconform-ably capping basement rocks at ~2 km elevation. The identification of biozone MMi 12a (7.81-8.35 Ma) from planktic foraminifera in the upper part of the section provides the tightest constraint on the age, which is further limited to 8.35-8.108 Ma as a result of the reverse polarity of the collected samples (chron 4r.lr or 4r.2r). This provides a limiting age for the onset of surface uplift at the margin of one of the world's major orogenic plateaus, from which an average uplift rate of 0.24-0.25 mm/yr can be calculated.Subhorizontal beds of the uppermostmarine sediments exposed throughout theMut-Ermenek Basin suggest minimal local-ized deformation, with just minor faultingat the basin margin and broad antiformaldeformation across the basin. This impliesthat the post-8 Ma uplift mechanism must berooted deep within the crust or in the uppermantle. Published Pn-wave velocity data forthe region are compatible with topographycompensated by asthenosphere across thesouthern margin of the plateau, showing aclose match to the highest topography when elevations are filtered with a 100-km-wide smoothing window. Uplift along the southern margin of the Central Anatolian Plateau is also reflected by the pattern of Miocene marine sediments capping the margin, which form an asymmetric drape fold over the topography. These observations, together with tomographic evidence for slab steepening and break-off beneath the Eastern Anatolian Plateau, suggest that at least some of the ~2 km of post-8 Ma uplift of the southern Central Anatolian Plateau margin is compensated by low-density asthenospheric mantle that upwelled following slab break-off.