Abstract ID: 3.11871 | Accepted as Talk | Talk/Oral | TBA | TBA

Located between the Pir Panjal towards the south and the Greater Himalaya to the north, the high altitude mountain region of the Chandrabhaga basin reflects average elevations of ~4000 m asl and the highest peaks at ~5500-6000 m asl. The region has historically experienced a transitory climate with periods of intensification of the Mid Latitude Westerlies (MLW) and the Indian Summer Monsoon (ISM). The region presently bears 845 glaciers of varying sizes. Paleoclimatic studies using OSL and CRN 10Be dating techniques, suggest of several episodes of glacial expansion since LLGM. The basin, majorly composed of Higher Himalayan Crystalline rocks, preserves evidences of the continuum of glacial, paraglacial and periglacial processes. Preliminary studies relied heavily upon geomorphological mapping and discrete OSL dating from a Lacustrine formation, which placed Khanjar stage of glacial expansion at early Holocene ~8-6 ka. The dates also suggested of glacial expansion in the Gumba-Chaturdhani glacier complex between ~8-6 ka and subsequent proglacial lake formation. Adoption of OSL dating approach from sampling location ~250 m apart, reveals the longevity of the lacustrine formation on the trunk valley between ~30-6 ka, post LLGM (~35 ka), presumably due to glacial blockade. The disparity in the dates from largely the same location can be explained through the processes active on the landscape, selection of sampling sites and nature of zeroing of Quartz before deposition. However, the revelation of older Radiocarbon (14C AMS) dates calibrated for age depth from an identified thermokarst lake, formed on water-vacated lacustrine sediment section at the same site on a higher elevation; reveals the initiation of periglacial activities at ~22,000-23,000 cal yrs BP from a section ~1 m from the top and continuation until recent times with periods of lull in between. These periods of quiescence in periglacial sedimentation rates indicate onset of weaker glaciations, not potent enough to wipe out the sediment assemblage. The Gumba thermokarst lake has been continuously fed by permafrost melt-waters from Turf Bank Lobe type Solifuction lobes, making the chronological reconstruction of the succession of glacial-postglacial and periglacial Quaternary processes possible.