HOLOCENE SW MONSOON INTENSITY SHIFTS RECORDED IN PROVENANCE CHANGES OF THE GANGES-BRAHMAPUTRA DELTA SEDIMENTS

The Ganges-Brahmaputra river system has been shown to respond rapidly to climate change in terms of river discharge, sediment load, and rate of deposition.

These properties have seen an order of magnitude shift during the Holocene from the present mean conditions in response to changes in summer SW monsoon intensity. These variations in climate have been recorded in the sediments of the G-B delta. Using the unique geochemical properties of the Himalayan source areas, we observe changes in sediment provenance that correlate with the increase in summer SW monsoon intensity between 7 and 9 ka. To note these provenance changes, we are examining the Sr isotope composition of the sediments as well as mineralogy, and elemental abundances. Nd isotope composition will strengthen our understanding of these provenance changes, and the use of clay mineralogy and major elemental abundances is helping us to reconstruct the weathering pattern of these sediments in the delta. With this information, we will be able to reconstruct the behavior of the delta response during the changing monsoon conditions of the Holocene.