Cosmogenic 36Cl surface exposure dating of glacial landforms on Mt. Barla (SW Turkey)

Abstract

Investigating Quaternary glaciations by terrestrial cosmogenic nuclide dating provides unique insights into glacial landscapes. However, postglacial processes may reshape these topographies via weathering, erosion and deposition, especially after the glaciers have entirely disappeared. Understanding the timing of Quaternary glaciations in the areas developed under different geomorphological processes may be challenging. In this study, we produced a detailed geomorphological map of Mt. Barla in the Western Taurus Mountains of Turkey. We found that geomorphological processes such as karstification and mass movements provided favourable settings for the valleys to be carved by glaciers during the Late Pleistocene. We applied in-situ cosmogenic 36Cl surface exposure dating to moraine boulders to reveal the glacial chronology and the geomorphological evolution. We dated moraine boulders (n = 11) from two glacial valleys that show at least two and possibly three deglaciations during the Late Pleistocene. For Gedik Valley, the left lateral moraine marks the Late-glacial glacier retreat by 16.6 ± 2.6 ka (MIS 2). On the other hand, the terminal moraine indicates that the most extensive glaciation occurred at 42.1 ± 5.2 ka (pre-global LGM) in this valley. The outer terminal moraine age (45.5 ± 6.8 ka) in Kapıdere Valley confirms this MIS 3 extension. Our results also imply even a possible earlier glaciation in Kapıdere Valley at 78.5 ± 17.6 ka (MIS 5), even though more data are needed to confirm this extent.