Abstract

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 Başyayla section (Mut-Ermenek Basin) within the Mut and Köselerli Formations suggests a Tortonian age for marine sediments unconformably 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.1r 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 uppermost marine sediments exposed throughout the Mut-Ermenek Basin suggest minimal localized deformation, with just minor faulting at the basin margin and broad antiformal deformation across the basin. This implies that the post–8 Ma uplift mechanism must be rooted deep within the crust or in the upper mantle. Published Pn-wave velocity data for the region are compatible with topography compensated by asthenosphere across the southern margin of the plateau, showing a close 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.

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