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

Lead Research Organisation: Lancaster University
Department Name: Lancaster Environment Centre

Abstract

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.

Planned Impact

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.
 
Description 1) Rapid exhumation of the eastern corner of the Himalayas commenced roughly 4 million years ago. 2) rutile U-Pb dating is a good tool to determine this, whilst Ar-Ar mica dating and apatite U-Pb dating are not.
Exploitation Route continuing collaboration with shipbaord and shorebased IODP Exp 354 participants.
Sectors Environment,Other

 
Description Ar-Ar analyses 
Organisation University of Glasgow
Department Scottish Universities Environmental Research Centre
Country United Kingdom 
Sector Academic/University 
PI Contribution provision of samples, interpretation of results, lead towards publication.
Collaborator Contribution analysis of mica grains by Ar-Ar analysis
Impact one paper in prep
Start Year 2016
 
Description U-Pb zircon dating 
Organisation University of Colorado Boulder
Country United States 
Sector Academic/University 
PI Contribution interpretation of data leading to join publication
Collaborator Contribution analysis and funding of same, contributing to writing of paper and data interpretation.
Impact one publication currently in review
Start Year 2015
 
Description Zircon fission track dating 
Organisation Birkbeck, University of London
Department Department of Earth and Planetary Sciences
Country United Kingdom 
Sector Academic/University 
PI Contribution provision of samples ad ultimately interpretation of data
Collaborator Contribution analysis of zircons by fission track
Impact in progress
Start Year 2015
 
Description rutile and apatite U-Pb dating 
Organisation Trinity College Dublin
Country Ireland 
Sector Academic/University 
PI Contribution lead in interpretation of data and writing of publication
Collaborator Contribution analysis of samples and co-interpretation of data and paper writing
Impact one paper currently in prep
Start Year 2016