Glacially derived material in an Inner Mongolian desert lake during Marine Isotope Stage 2

Abstract

Establishing the precise timing of continental glacial dynamics and abrupt high-latitude climate events is crucial to understanding the causes of global climate change. Multi-proxy records in a lake sediment core from arid Inner Mongolia (Wuliangsuhai Lake) that show two distinct glacially derived sedimentation events at approx. 26.2-21.8 and approx. 17.3-11.5k cal a BP are presented. Fine sediments from the Last Glacial Maximum separate these glacially derived coarse sediments. Within these intervals, the occurrence of granite clasts at approx. 24-23.5, 17.3-17 and 15.6-14.1k cal a BP implies either sediment discharge by meltwater as well as strong current flow in the Yellow River and/or sediment influx through hill-slope mass wasting and landsliding from the nearby Yin Mountains. Surface microfeatures of quartz grains and spot elemental analysis of black specks in these intervals, however, indicate that physical weathering is dominant and that the provenance of the rocks is probably from a glacial source. To the best of our knowledge, this is the first time glacier-derived materials have been detected in any desert lake in the Yellow River basin. The occurrence of granite clasts roughly correlates with Heinrich events in the North Atlantic, suggesting synchronous ice sheet dynamics in high- and mid-latitude regions during the Last Glacial period. Although our data provide unprecedented evidence for the influence of glacier-related processes in arid Inner Mongolia, further well-dated records are clearly needed to re-evaluate the correlative inference drawn between granite clast layers in Wuliangsuhai Lake and Heinrich events in the North Atlantic.