Weathering and climate linkage at seasonal to kilo year timescales evidence from water and sediment chemistry

Abstract

Continental erosion plays a dominant role in global biogeochemical and climatic cycles Intensity of this land surface erosion process is disproportionally higher in the tropics mainly due to its conducive climate rainfall and temperature The main objective of this thesis work is to investigate the interaction between erosion and climate over multiple timescales ranging from seasonal to kilo years Towards this geochemical and isotopic analyses of paleo archives sedimentary records from the Arabian Sea and upper Indus Zanskar River basin and speleothem and weekly variation of river water chemistry Brahmaputra River have been carried out The chronology of the speleothem 9200 3950 yrs BP collected from the Gupteswar Cave Odisha India was established using U Th isotopic systematic whereas the age ranges for the Zanskar sediment section 22400 1450 yrs BP and two Arabian Sea cores SSK40 GC06 3560 yrs BP recent SSK40 GC10 7150 800 yrs BP were constrained using radiocarbon ages Seasonality in chemical erosion pattern of the Brahmaputra River basin Time series analyses of the Brahmaputra River Guwahati India water chemistry show seasonal changes The degree of seasonality for the elemental abundances and their ratios however is less pronounced at Guwahati when compared to those with other Himalayan Ganga and Salween rivers The monthly averaged Ca Si ratios for the Brahmaputra show minimal 6 variation compared to that 17 observed for the Ganga outflow points to the minimal role of runoff in regulating the erosion pattern of this river Inverse model calculations estimated the silicate derived fraction of cations and Sr for monsoon and non 8208 monsoon seasons respectively are statistically indifferent Observations from this study suggest that the erosion intensity in the Brahmaputra basin is not limited by runoff water 8208 rock interaction time and is more regulated by rapid mechanical erosion at around eastern syntaxis Reconstruction of Holocene variability of the erosion patterns using marine records Geochemica