PROVENANCE ANALYSIS OF PALEOFLOOD SEQUENCE IN UPPER GANGA CATCHMENT

Abstract

Floods may find their manifestations in sedimentological records as massive sand beds on fluvial terraces, organic debris flow, and Slack water deposits. We analyzed the slack-water deposits formed due to paleofloods and exposed near the bank of river Alaknanda at Bhainswara, Srinagar. Provenance estimation was carried out using petrographic methods; seven out of eleven units were found to be originated in Higher Himalayas indicating that the flood was GLOF (Glacial Lake Outburst Floods) sourced. Four out of eleven units that found their provenance in the Lesser Himalayas were relatively younger and occurred due to LLOFs (Landslide Lake Outburst Floods). Further, the chronology of these flood events was correlated with the major climatic events in the past and the results have shown that during the period of the Little Ice Age (LIA;1305-1850 years AD), the floods were GLOF sourced and were less frequent probably due to the suppression of ISM(Indian Summer Monsoon) during LIA. During the warm and wet phase the provenance of flood shifted to the Lesser Himalaya and become LLOF sourced due amplification of landslide through intensification of ISM, intensification of ISM also caused the younger floods to be more frequent.