Paleoglaciology of Shaluli Shan, southeastern Tibetan Plateau

Abstract: Reconstructing the paleoglaciation of the Tibetan Plateau is critical to understanding linkages between regional climate changes and global climate changes. This work focuses on the paleoglaciology of the Shaluli Shan Mountain area in the southeastern Tibetan Plateau. Multiple approaches, including geomorphological mapping, field assessment, cosmogenic nuclide exposure dating, and numerical glacier modeling are employed to reconstruct the extent, timing, erosion patterns, basal thermal regime, and ice dynamic of past glaciation of the Shaluli Shan. Detailed geomorphological mapping and analysis provide evidence for multiple past glaciations involving valley glaciers and small ice fields in the high mountains and ice caps on low-relief plateaus at intermediate elevations. Ice cap glaciation on the low-relief Haizishan Plateau produced glacial landforms in a zonal pattern, suggesting that the Haizishan paleo-ice cap had a complex basal thermal regime. 10Be exposure ages for glacial erratics and till depth profiles constrain three major glaciations in the Shaluli Shan: pre global Last Glacial Maximum (gLGM) (with minimum ages at 102.3 ± 10.0 – 183.6 ± 17.0 ka), gLGM (21.6 ± 2.0 ka), and Late Glacial (13.0 ± 1.2 – 17.1 ± 1.6 ka) . Extensive glacier expansion in the Shaluli Shan during Marine Isotope Stage (MIS) 6 and gLGM, and the lack of evidence of glaciation during MIS 4 and 3, suggests that the extent and timing of glaciations in the southeastern Tibetan Plateau are synchronized with northern Hemisphere climate changes. The glacial erosion depth constraints based on 10Be and 26Al concentrations in bedrock, glacial erratics, and till depth profiles indicate a complex glacial erosion pattern during the gLGM and Late Glacial, consistent with the hypothesis of complex basal thermal regime of Haizishan paleo-ice cap. Numerical model simulations of a Haizishan ice cap also predict a complex basal thermal regime and indicate high sensitivity of the ice cap to past temperature.