RECONSTRUCTING HIGH-RESOLUTION HOLOCENE GLACIAL CHRONOSTRATIGRAPHIES IN THE HIMALAYA

Regionally variable retreat of Himalayan glaciers highlighted their complexity and dynamics to present climate change. A major limitation in our understanding of these high mountain glaciers has been attributed to a paucity of comprehensive spatiotemporal knowledge of Holocene glaciation in the orogen despite the preservation of abundant geomorphological records. To gain insight of recent Himalayan glacial fluctuations, young moraines have been mapped in the field with the aid of Google Earth satellite imagery and GPS and dated using cosmogenic ¹⁰Be surface exposure dating in the NW Himalaya. Seventy three new moraine erratic samples were collected in ten different glaciated valleys of the Zanskar, the Greater Himalaya and the Pir Panjal ranges for ¹⁰Be analysis. Forty one of the total samples has already been measured. These new and 424 published Holocene ¹⁰Be ages are compiled to reconstruct high-resolution Holocene glacial advances across the Himalayan-Tibetan orogen. In addition, to gain insight of spatial pattern of Holocene glacial advances, glaciated valleys with similar present climate are clustered together into six broad groups using the climate data generated from the CRU CL 2.0 surface climate data series (1961-1990) and Tropical Rainfall Measuring Mission precipitation data (1998 to 2009) and applying Cluster Analysis and Principal component analysis. Preliminary reconstruction of regional glacial stages indicates several short-lived regional glacial advances during the Holocene across the orogen. These short-term glacial advances may have occurred during ~12.4, ~10.1, ~9.1, ~7.9, ~5.0, ~4.2, ~3.3, ~1.3, ~0.74, and ~0.33 ka with more extensive advances during the early Holocene and progressively limited advances in the later part. Regional analysis also confirms that continental sub-polar glaciers in the NW Himalaya and Tibet experienced relatively limited change in ΔELA during the Holocene than the warm-wet temperate glaciers in the S and SE. Overall, regionally uniform extensive early Holocene glacial advances correspond to stronger monsoonal precipitation, whereas cooler late Holocene glacial advances, including the peak at ~7.9 ka is likely synchronous with decline in regional temperature as well as monsoon precipitation and likely corresponds to changes in the N Atlantic.