Constraining uplift of the southern margin of the Central Anatolian Plateau from biostratigraphy and 87Sr/86Sr stratigraphy on the highest marine sediments of the Mut Basin (Southern Turkey)

At the northern margin of the Mut-Ermenek Basin (Southern Turkey), well exposed, undeformed Miocene marine deposits cap the basement rocks of the southern margin of the Central Anatolian Plateau (CAP). From the Basyayla section, which ranges from 1781 m a.s.l. at the base to 1839 m a.s.l. at the top, we collected 24 samples, for a total thickness of about 40 m of the Köselerli Fm. Micropaleontological analyses were performed on calcareous nannofossil, ostracod, bryozoa, benthonic and planktonic foraminifera, and macroforaminifera assemblages to discern paleoecological characteristics of the marine paleoenvironment in the Basyayla area and to define the age of the Basyayla section. Also for this latter purpose, Sr ratios (87Sr/86Sr) were measured on tests of benthonic and planktonic foraminifera as well as on benthonic planar macroforaminifera (Heterostegina gr. costata and H. papyracea). The different ostracod assemblages recognized along the Başyayla section record a littoral marine environment with a depth between the outer infralittoral (40 m) to the inner circalittoral (120 m). Most of the identified ostracod species show a wide Neogene stratigraphical distribution, but the concomitant presence of Cytherella vulgata and Aurila freudenthali (last record in the Tortonian) and Semicytherura velata (late Tortonian-Present) constrains the age of the studied section to within the late Tortonian. Moreover, the occurrence in the upper part of the Basyayla section of both Globigerinoides extremus and Catapsydrax parvulus allow us to define the Globigerinoides extremus-Globorotalia suterae Interval Subzone (MMi 12a), which ranges from 8.35 to 7.81 Ma (upper Tortonian). 87 Sr/86Sr measurements were performed on 5 samples of the study section from tests of benthonic planar foraminifera (Heterostegina spp.), and benthonic and planktonic foraminifera. A total of 19 sample aliquots were analysed for 87Sr/86Sr measurements (11 Heterostegina spp., 3 planktonic, 5 benthonic) giving a range of values between 0.708821 and 0.708848 for a range of LOWESS IV estimated ages of 12.71 to 11.20 Ma. Three oysters sampled ~30 m above the top of the Basyayla section yielded 87Sr/86Sr ratio values between 0.708824 and 0.708833, for a range of LOWESS IV estimated ages of 12.58 to 12.17 Ma. The discrepancy between the 87Sr/86Sr estimated ages and the biochronology for the Basyayla section point to a strong departure from the global ocean Sr curve of the Tortonian seawater of the Mut Basin. The stratigraphical study of the Basyayla section, which represents the highest marine deposits capping the basement rocks of the Mut-Ermenek basin so far sampled, point to an age younger than the late Tortonian (8.35-7.81 Ma) for the start of uplift of the CAP southern margin.