ABSTRACT

Dr. Elizabeth L. Chamberlain has been granted an NSF EAR Postdoctoral Fellowship to carry out research and education plans at Columbia University, Vanderbilt University, and Wageningen University. The project will make use of recent innovations by Dr. Chamberlain regarding optically stimulated luminescence (OSL) dating. OSL estimates the time of sediment deposition based on trapped charges that accumulate in quartz grains when they are removed from sunlight. She will apply OSL to the Ganges-Brahmaputra Delta, Bangladesh, to determine the mechanisms and timescales of delta evolution. Specifically, this work will explore the connection between river and seismic (earthquake) processes in a large delta. Findings will describe sediment delivery to floodplains and coasts, a key factor in sustaining deltas under accelerated rates of sea-level rise. In addition, the research will provide new information about river-seismic geohazards by investigating how often large earthquakes occur and whether earthquakes are capable of forcing rivers to spontaneously change course. The anticipated findings are relevant to coastal management within the densely populated nation of Bangladesh and in other coastal regions worldwide such as the Mississippi Delta, U.S. This work will also contribute to methodological development of the OSL tool. The research will facilitate knowledge transfer between work groups in the U.S., The Netherlands, and Bangladesh and will support student education by engaging Bangladeshi M. Sci. students in field work and a U.S. undergraduate in laboratory work.
The Ganges-Brahmaputra Delta offers a rare opportunity to explore coupled fluvial-tectonic processes, given its extensive river channel network and position along several actively deforming plate boundaries. In 2018, Dr. Chamberlain and colleagues identified a cluster of paleo-seismite structures in the Late Holocene Ganges floodplain that include large sand dikes and soft sediment deformation. Located on the edge of an immense (>1.5 km-wide) relict and underfilled channel scar, these features suggest a link between large seismic events and major channel avulsions. Dr. Chamberlain will use her recently published OSL protocol to date seismite, paleochannel bed and fill, point bar, and adjacent floodplain deposits, thereby testing two processes that may regulate the avulsion timescales of large rivers: (1) enhanced avulsion frequency through forcing by large, high-magnitude seismic events, and (2) suppressed avulsion frequency through aggradation of the delta plain fed by small distributary channels. A component of this investigation will explore the development of novel luminescence geochronology approaches to determine the timing of sand-dike emplacement. Dr. Chamberlain's research will contribute to both the theoretical and applied knowledge of delta dynamics, and to the advancement of luminescence tools by providing a new method to date structures previously not amenable to dating.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

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