The exhumation history of the Himalayan orogen determined from Bengal Fan sedimentary record (IODP Leg 354)

The Himalayas are a type example of continent-continent collision, and resultant mountain building processes. Geologists can look at the rocks in the mountain belt itself to determine its evolution, but sometimes the evidence in the rocks in the mountain belt itself is obscured by later increases in the temperature and pressure that the rocks were subjected to, which overprints the evidence. Sediments eroded off the evolving Himalaya are deposited in the Bengal Fan, and these can provide an archive of the erosion of the history of the mountain belt through time which has not been obscured my later metamorphism, as the material was eroded and removed from the mountain belt prior to these later overprinting events. This project will analyse minerals that cooled as they were exhumed from deoth towards the surface in the mountain belt. The project will date the minerals to determine the time they cooled, and this will provide information on when the rocks were exhumed and how fast they exhumed, thus providing information on when and how fast the mountain belt grew.

Academic impact: this is the first time that an attempt will be made to drill the Bengal Fan to its base, and thus the first complete Himalayan erosion record. This will be used by those who investigate tectonic-erosion interactions and those who investigate the effect of increasing erosion on global climate. Both require an erosion history to inform their models.

Private sector impact: this region has hydrocarbon prospectivity, as evidenced by the presence of a number of hydrocarbon companies working onshore and offshore in Bangladesh and Myanmar. A knowledge of the sedimentation in the fan is invaluable for the construction of palaeogeographic maps, and thus better understanding of where hydrocarbon traps may lie.