10 Be Exposure Age Dating of Moraine Boulders and Glacially Polished Bedrock Surfaces in Karakoram and Ladakh Ranges, NW Himalaya: Implications in Quaternary Glaciation Studies

• Published in: Journal of geophysical research. Earth surface 2023-11, Vol.128 (11)
• Main Authors: Jena, Partha Sarathi, Bhushan, Ravi, Sharma, Shubhra, Dabhi, Ankur J., Ajay, Shivam, Raj, Harsh, Juyal, Navin
• Format: Article
• Language: English
• ISSN: 2169-9003; 2169-9011
• DOI: 10.1029/2023JF007216

Terrestrial cosmogenic nuclide (TCN) dating has emerged as one of the most useful techniques in the last two decades for quantifying geomorphological processes and building the chronology of late Quaternary glacial advances/retreats. The chronology based on TCN and optically stimulated luminescence (OSL) dating of glacial landforms from the northwestern (NW) Himalaya suggests that glaciers responded to a complex interaction between temperature and moisture essentially derived from either of the climate systems, the Indian Summer Monsoon (ISM) and the Mid‐latitude Westerlies (MLW). The discrepancies between the TCN ages obtained on moraine boulders/bedrock surfaces, and the OSL ages on the stratigraphically equivalent deposits, highlighted the need for a detailed investigation. The present study attempts to build the chronology of Quaternary glaciation events in the Karakoram and Ladakh Ranges using TCN dating of stratigraphically constrained moraine boulders and striated bedrock surfaces. The TCN ages from glacially eroded surfaces (GES) having prominent striations are narrowly clustered around the Marine Isotopic Stage‐2 (MIS‐2). Agreement between GES TCN ages and OSL ages on the stratigraphically equivalent moraines suggests negligible geological inheritance. The glacial advance during MIS‐2 can be attributed to the combined effect of reduction in north hemispheric insolation and enhanced westerly precipitation. However, relict non‐glacial surfaces and moraine boulders with minimal ice flow modifications yield wide age distributions, most likely suggesting denudational events (interglacials) and/or contribution from tributary valley flanks. Quaternary glacial advances and retreats in the northwestern (NW) Himalaya respond to a complex interaction between climatic parameters, that is, temperature and moisture essentially derived from the two contrasting weather systems viz., the Indian Summer Monsoon (ISM) and the Mid‐latitude Westerlies (MLW). In this study, we employed terrestrial cosmogenic nuclide dating of stratigraphically constrained moraine boulders and striated bedrock surfaces to understand the dynamics of late Quaternary glaciation in the Karakoram and Ladakh ranges. The exposure ages obtained from glacially eroded surfaces (GES) show a narrow cluster around the Marine Isotopic Stage‐2 (MIS‐2), a period when the northern hemispheric insolation was low resulting in a temperature decline. The glacial advance during MIS‐2 is attributed to the comb