107 D10. Recent Advances in Geophysics/Geodynamics (Posters)

Monday, 23 September 2019
9:00 AM - 6:30 PM
Hall AB, North Building

GRAVITY ANALYSIS OF THE BHUTAN HIMALAYAN OROGENY

Paper number: 107-9
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

The Bhutan Himalayan orogenic belt, located within the eastern quarter of the Himalayan orogenic belt, is mostly known from the balanced geological cross-sections derived along roads and models derived from the sparsely distributed broadband seismic data. In order to obtain more higher resolved lithospheric model of the Bhutan Himalayan orogenic belt, detailed gravity surveys have been conducted along the all available roads in Bhutan since 2015. Approximately, 5300 gravity stations, with the station interval ranging between 0.5 and 1 km, have been acquired along with differential GPS data to obtain submeter elevation data. The gravity data were processed into complete Bouguer gravity anomalies using a 10 meter DEM obtained from the Bhutan Geological Survey. In addition, using the 10m DEM and lithospheric thicknesses derived from the broadband seismic models, isostatic residual gravity data were obtained. The complete Bouguer and isostatic residual gravity anomalies were analyzed using a variety of map methods including Euler deconvolution, wavelength filtering, and derivative methods. Residual gravity anomaly maps derived using wavelength filtering clearly indicate significant along strike variations in the density structures of the orogenic belt. The residual gravity anomaly maps indicate gravity minima over the Subhimalayan units and the modern foreland basin, however, gravity maxima are observed mostly over the Lesser Himalayan region which may be explained by the presence of quartzitic rocks. Two-dimensional roughly north-south trending gravity models were constructed to determine the crustal structure using constraints from the recent seismic models. The modeling indicate that the long wavelength anomalies are associated with variations of the depth to the Moho and are caused by the flexure of Indian plate beneath Bhutan Himalaya. The modelling shows that the Moho depths increases towards the north from 50 km beneath Main Frontal Thrust to 75 km beneath the Greater Himalayan sequence in the western Bhutan. Conversely, such substantial variations of Moho depths is not detected beneath the central Bhutan, which is supportive to the seismic results.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-331591

© Copyright 2019 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.