Date of Graduation

Spring 2018

Degree

Master of Science in Geospatial Sciences

Department

Geography, Geology, and Planning

Committee Chair

Kevin Mickus

Keywords

Bhutan Himalaya, Bouguer gravity anomaly, crustal structure, gravity modeling.

Subject Categories

Geophysics and Seismology

Abstract

To expand the current understanding of lithospheric structure within Bhutan Himalaya, a detailed gravity survey was conducted for the first time along the all major roads within western and central Bhutan in 2015-2017. The acquired Bouguer gravity anomaly data were analyzed and interpreted using map methods (wavelength filtering and Euler deconvolution) which clearly indicate that there are substantial anomalies due to crustal density sources and a complex Himalayan geology. Four two-dimensional gravity models across the Himalayan tectonostratigraphic units were constructed to determine the crustal density structure using constraints from the geological and geophysical studies. The results support that the long wavelength gravity anomalies are associated with variations of the Moho depth that are caused by the flexure of Indian plate. The modelling revealed along-strike differences in the crustal thickness beneath Bhutan Himalaya. In western Bhutan, the Moho depth increases towards the north from ~50 km beneath the Main Frontal Thrust to ~70 km beneath the Greater Himalaya, whereas in central Bhutan the Moho was imaged at depth varying between ~50 and ~60 km. The Bhutan Himalayan orogenic wedge is detached from the underlying Indian plate along the basal decollement known as the Main Himalayan Thrust at a depth increasing from 7-10 km beneath Sub and Lesser Himalaya to ~30 km beneath the Greater Himalaya.

Copyright

© Kinzang Duba

Open Access

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