Collaborative Research: Subduction below Extreme Sedimentation – A multidisciplinary transect from the Ganges-Brahmaputra Delta to the IndoBurma Backarc

DESCRIPTION: This project involves a study of a poorly understood and unique geologic setting: a subduction zone that has an exceptionally large amount of sediment, the Ganges-Brahmaputra Delta (GBD). The GBD is the world's most extreme example of sediment accretion, with sediments up to 19 km thick in the Bengal Basin. The region has little volcanism compared to other subduction zones and a large seismic risk; recent GPS results indicate that this highly oblique plate boundary is locked with the potential for a M8.2 earthquake that could affect more than 140 million people. The project is motivated by the question of how the extreme sedimentation affects subduction phenomena. The project will involve a multi-institution, multi-nation collaboration involving scientists from Bangladesh, India and Myanmar, Singapore, Norway, and the U.S. The PIs will focus on three major issues: 1) Neogene growth of the accretionary prism and earthquake hazard; 2) Crustal shortening and deformation across the IndoBurma Ranges and Burma Basin; and 3) Incoming fluid content and volcanism. To address these issues, they will deploy seismic, GPS, magnetotellurics and gravity sensors in a transect from the deformation front to the backarc in the Bangladesh-India-Myanmar Array (BIMA). Structural geology, geochemistry and thermochronology will provide additional constraints. They will use a broad program of numerical and laboratory modeling to integrate and interpret the results from the multiple data sets. This end-member case of extreme sediment subduction has broad implications for understanding these issues at all subduction zones.