Start |Grid View | Author Index | View Uploaded Presentations | Meeting Information

GSA Connects 2022 meeting in Denver, Colorado

Paper No. 108-5
Presentation Time: 2:35 PM

THE EXHUMATION HISTORY OF THE GREATER HIMALAYAN SEQUENCE, CENTRAL NEPAL


PYE, Alexandra1, HODGES, Kip V.1, EHLERS, Todd A.2, VAN SOEST, Matthijs C.1, MCDONALD, Christopher S.1 and BHANDARI, Basant3, (1)School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, (2)Department of Geosciences, University of Tübingen, Tübingen, 72074, Germany, (3)Tri-Chandra Campus, Tribhuvan University, Ghantaghar, Kathmandu, AZ 44605, Nepal

One of the fundamental questions faced by the geosciences today is the relative influences of climate and tectonics on how landscapes have evolved through geologic time. Understanding the spatial and temporal variation in the exhumation history across a tectonically active mountain range can help shed some light on this problem.

The Himalaya is one of the planet’s most useful natural laboratories to work on this issue. The South Tibetan detachment system (STDS), a collection of Oligocene-Miocene aged normal sense structures, stretches over 2000 km across the entire range and outcrops at roughly the location of a dramatic topographic and orographic transition. The Annapurna region in central Nepal is home to excellent exposures of these structures, as well as footwall rocks rich in accessory minerals allowing detailed thermochronometric and geochronometric studies.

Here we present new results from thermochronology transects in the footwall of basal structures of the STDS in both the Kali Gandaki and Marsyandi drainages (the Annapurna and Chame detachments). New constraints based on (U-Th)/Pb dating of accessory minerals in variably deformed leucogranites within the Annapurna and Chame detachment zones are consistent with the interpretation that the two are corelative and were active simultaneously during the mid-Miocene.

One dimensional inverse thermal-kinematic modeling using Pecube-D of 40Ar/39Ar muscovite and biotite, U/Pb titanite, and (U-Th)/He titanite, zircon and apatite dates reveal a decrease in exhumation rate at ~12 Ma followed by a dramatic increase at ~3 Ma in both drainages. Given the temporal agreement with the age of deformation on the Annapurna detachment, we suggest that this initial decrease in exhumation rate was due to cessation of slip on the Chame and Annapurna detachments. The timing of the dramatic ~ 3 Ma increase in exhumation rate coincides with the initiation of the modern Indian summer monsoon and the increase of the East Asian winter monsoon.

Session No. 108

T1. Advances and Applications of Thermochronology in Tectonic, Magmatic, Basin, and Geomorphic Studies II
Monday, 10 October 2022: 1:30 PM-5:30 PM
601 (Colorado Convention Center)
Geological Society of America Abstracts with Programs. Vol 54, No. 5
doi: 10.1130/abs/2022AM-380519
© Copyright 2022 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.
Back to: T1. Advances and Applications of Thermochronology in Tectonic, Magmatic, Basin, and Geomorphic Studies II
<< Previous Abstract | Next Abstract >>