Document Type
Thesis
Abstract
Clay mineralogy and grain-size of Ganges and Brahmaputra River sediments is investigated from six boreholes of Late Quaternary deposits from the delta plain of Bangladesh. In recent studies, clay mineralogy has been used to determine river provenance in modern delta-plain sediments and as an indicator of climatic and tectonic changes in Bengal Fan sediments (Bouquillon et al., 1990; Derry and France-Lanord, 1996; Colin et al., 1999; Heroy et al., 2003). Kaolinite abundance in late Quaternary borehole sediments is found to be diagnostic of Brahmaputra River provenance. Illite, chlorite, and smectite are not diagnostic of provenance, despite high smectite abundance in river grab samples by Heroy et al. (2003). Boreholes do not show a consistent trend in chemically (smectite + kaolinite) versus physically (illite + chlorite) weathered clays since the Last Glacial Maximum. BH-13 from the Sylhet basin show a possible decrease in chemically weathered clays over the Holocene, which may indicate the influence of local weathering processes. High variability in clay abundance of a borehole near the paleo Brahmaputra (BH-7) may indicate seasonal bias due to high deposition rates. Combined with a knowledge of deposition rates and processes, the lack of a consistent weathering signal in delta plain sediments suggests that the observed Bengal Fan weathering signal may be controlled by changes in river provenance rather than a consistent shift in weathering on the delta-plain.
Date Awarded
2005
Department
Geology
Advisor 1
Steven Kuehl
Recommended Citation
Tennant, Elizabeth J., "Late Quaternary Climate and Provenance Signals of the Ganges-Brahmaputra Delta Plain, Bangladesh" (2005). Geology Senior Theses. William & Mary. Paper 147.
https://scholarworks.wm.edu/geologyseniors/147
