Timing of Thrusting in the Nyainqentanglha Shan of Southeastern Tibet

Matthew Fabijanic
The University of Arizona, Department of Geosciences
Tucson, AZ
[email protected]

Growth structure conglomerates provide a record of syn- and post-depositional thrusting along nearby thrusts. This study will examine previously unmapped conglomerates situated between two parallel thrusts in the vicinity of Lagen La pass in the Nyainqentanglha Shan Mountains of southeastern Tibet. Fine-scale mapping (1:10,000 and 1:25,000) will allow correlation of local unconformities and conglomerate beds between disparate outcrops, in order to gain an integrated view of how thrusting varied along strike. Conglomerate clast counts, sandstone petrographic point counts, and paleocurrent indicators will reveal the conglomerate’s provenance history. Finally, geochronologic analysis of samples will constrain the timing and magnitude of the thrusting which rotated these conglomerate beds. Combining detailed structural analysis with provenance data will allow for incremental retro-deformation of the growth structures, and allow for temporal constraints to be placed on movements along the thrust faults. New information on the timing, magnitude, and style of thrusting in this area will shed light on regional tectonic events in Tibet, and specifically how Tibetan crust was shortened prior to the Himalayan orogeny.

AAPG Search and Discovery Article #90033©2004 AAPG Foundation Grants-in-Aid