Glacial landforms as palaeo-environmental archives in the Eastern Himalaya: A case study of Changme Khangpu glacial valley in Sikkim Himalaya,India

Abstract

This study attempts to reconstruct the glacial history of the Upper Changme Khangpu Basin (CKB), an eastern tributary of the River Tista in the Eastern Himalaya, using radiocarbon (¹⁴C) method, supplemented by sedimentological and mineralogical analyzes. Despite being a monsoon-dominated glaciated region, the upper reaches of the basin still contain exceptionally well-preserved glacial landforms of the recent geological past. However, there remains a critical gap in understanding due to the lack of chronological studies to clarify and correlate the roles of climate and glacial interactions in an environment where intense monsoonal precipitation rapidly alters the landscape and glacier dynamics. In order to reconstruct the past glacier fluctuations and associated palaeoclimatic conditions, this study has employed a multi-proxy approach, integrating geomorphic feature mapping, sedimentological analysis, Accelerator Mass Spectrometry (AMS) ¹⁴C dating, alongside the Schmidt Hammer rebound data for relative age determination. The results have yielded a well-defined glacial chronology for the Late Quaternary in the CKB, identifying four distinct glacial advances of varying magnitudes. The extensive glacial phase (Phase-II) resulted in the blockage of the ablation valley, forming a ∼700 m-long proglacial lake. Subsequent glacial recession seems to have intensified the paraglacial processes which progressively reshaped and modified the earlier landforms. A new dataset of ¹⁴C ages (3.5 ka to 31.4 ka cal BP) indicates climatic oscillations during the intervening period. Post-glacial climatic shifts, particularly between 14.29 ka and 3.5 ka cal BP, show a regional correlation with climatic patterns observed in the Eastern Himalayas. Our finding underscores the need to further refine this enquiry to develop a robust glacial chronology of the basin using multiple modern geochronological techniques.