Integrating Forward Modeling and Unroofing Data from the Central Himalayan Thrust Belt, Western Nepal

The Himalayan thrust belt is often cited as an example of a thrust system which propagated from hinterland to foreland. Recent work using forward modeling and timing data reveal a detailed view of the evolution of the central Himalayan thrust belt from the footwall of the South Tibetan detachment system southward to the Main Frontal thrust. By using a reasonable configuration of undeformed stratigraphy, the surface deformation in western Nepal can be dynamically reproduced as essentially a forward propagating thrust belt from hinterland to foreland, with minor out-of-sequence thrust and normal faults. The data and the forward modeling support a conventional wedge model for the development of the central Himalayan thrust belt. In addition, a step-by-step view of the kinematic sequence is useful for understanding and bracketing erosion, the basin sediments, and geodynamic models.

These step-by-step reconstructions in conjuction with unroofing data derived from the synorogenic sediments in the Himalayan foreland basin can produce a detailed record of erosion in the Himalayan thrust belt. Conventional point counting data and isotopic data from the Bhainskati Formation, Dumri Formation and Siwalik Group, which have been dated using magnetostratigraphy, reveal a rich unroofing record in western Nepal. Each step of the structural kinematic sequence from the forwards models is correlated with the unroofing data from the synorogenic sediment. This study is the first to combine kinematic data with unroofing data to produce a series of 'snap shots' of how the Himalaya looked with respect to erosion from 25 Ma to the present. This study explores the link between erosion and evolution of the Himalayan thrust belt and the feedback between these two processes in the resulting Himalayan-Tibetan Orogenic system.