Naresh Rana

8000-year monsoonal record from Himalaya revealing reinforcement of tropical and global climate systems since mid-Holocene

We provide the first continuous Indian Summer Monsoon (ISM) climate record for the higher Himalayas (Kedarnath, India) by analyzing a 14C-dated peat sequence covering the last ~8000 years, with ~50 years temporal resolution. The ISM variability inferred using various proxies reveal striking similarity with the Greenland ice core (GISP2) temperature record and rapid denitrification changes recorded in the sediments off Peru. The Kedarnath record provides compelling evidence for a reorganization of the global climate system taking place at ~5.5 ka BP possibly after sea level stabilization and the advent of inter-annual climate variability governed by the modern ENSO phenomenon. The ISM record also captures warm-wet and cold-dry conditions during the Medieval Climate Anomaly and Little Ice Age, respectively.

Interpreting the geomorphometric indices for neotectonic implications: An example of Alaknanda valley, Garhwal Himalaya, India

Tectonic process can influence the erosion and exert the first order impression on hydrographic network of an area. Geomorphometry, a mathematical analysis of the configuration of the landforms, allows quantifying the degree of landform evolution and is widely used as a measure of tectonic deformation/uplift. Alaknanda valley lies in the tectonically active Garhwal Himalaya which has experienced two disastrous large earthquakes in the last two decades. Morphometric analyses of the valley were carried out in a fluvial erosion dominated regime and the morphometric indices were derived from the ASTER (30 m × 30 m pixel) Digital Elevation Model (DEM) using Arc GIS. The results of the analyses reveal two zones of high deformation/uplift in the valley, viz., the zone of high deformation proximal to the Main Central Thrust (MCT) in the Inner Lesser Himalaya (ILH) and the second zone of moderate deformation/uplift in the Outer Lesser Himalaya (OLH), south of the Tons Thrust (TT). The high deformation in the ILH is ascribed to the focussed convergence and high precipitation; however, the causes for the moderate deformation in the OLH are yet to be established.