Luminescence dating of late pleistocene glacial and glacio-fluvial sediments in the Central Himalaya, India

Abstract

The late Quaternary glacier advances in the Himalayan orogen exhibit a complex interplay of insolation induced changes in summer monsoon and winter westerlies. However, the relative contributions of these moisture sources in driving the glacier advances in the Himalaya are still being debated. Additionally, uncertainties about the timing, and hence the processes, responsible for driving the penultimate Last Glacial Maximum (LGM) in the Central Himalaya, still persist. The present study attempts to address some of these issues by employing detailed moraine stratigraphy supplemented with luminescence dating of three moraine and two relict lake sequences in the Kunti-Banar valley of the Central Himalaya, India. The study revealed that the penultimate glacier advance was significantly more extensive compared to its LGM counterpart. Stratigraphically and chronologically correlated sequences indicate that the penultimate glacial advance corresponded to the cool and dry Marine Isotope Stage 4 (MIS 4) and pluvial early to middle MIS 3. The restricted LGM glacier advance is dated to ∼23 ± 4 ka; while the youngest glacial advance is dated to ∼16.6 ± 0.4 ka and corresponds to the oldest Dryas (OD).Geomorphologically, the oldest Kunti-Banar glacier advance (KBGA)-I moraine was responsible for the obstruction of the meltwater stream leading to the formation of a proglacial lake around 30 ± 3 ka. Similarly, the KBGA-II moraine is overlain by relict lake sediments, with an age range of ∼15 ± 1 ka to present, implying that deglaciation has occurred prior to it. Evidence from the Dhauliganga valley resonates reasonably well with the pattern of glacier advances from Central Himalaya implying the influence of mid-latitude, synoptic-scale climatic perturbations. Particularly, there seems to be a coupling between the enhanced mid-latitude westerlies and phases of glacier advance, whereas the deglaciation phases correspond to the insolation driven enhanced monsoon periods.