| dc.description.abstract | The sedimentary archive of the Ganges-Brahmaputra river delta (G-B) records how the delta system responds to changing sediment and water supply, channel avulsions, and sea level rise. Through a combination of a robust field-based sediment core dataset, geochemical methods, and theoretical approaches, this research comprehensively investigates the Holocene G-B stratigraphic record using a sediment mass balance approach. We use the resulting sediment budget to document changes in sediment inputs under varying climate conditions and to link findings to potential impacts of anthropogenic alterations of the sediment supply through river linking and impoundments. This work highlights that sediment trapping may limit the natural resilience of the G-B to future sea-level changes. We also complete a thorough accounting of the physical characteristics of the sedimentary archive, enhancing the ability to predict subsurface variability, with implications for understanding hydrologic connectivity, self-organization of the delta system, groundwater availability, and contamination. Finally, we apply a novel application of cosmogenic radionuclides 10Be and 26Al to Holocene delta sediments to investigate whether observed fluctuations in Holocene sediment loads are linked to increased bedrock erosion in the Himalayas or remobilization of stored glacial sediments in the headwaters due to increased transport capability under a strengthened monsoon. This dissertation adds to the existing knowledge on landscape change and the fate of mega-deltas under increasing anthropogenic modification and predicted climate changes. By using the Holocene sediment record of past delta behavior, we are able to infer potential responses of the system to future perturbations. Since the early Holocene G-B environment and climate is often considered analogous to anticipated changes in the Anthropocene, a thorough understanding of the system during the recent past may provide geologically-supported insights into how the G-B may respond to river engineering projects, changing monsoon climate, and increasing sea level rise. | |
