Numerical Modeling of Cenozoic Compressional Events of Northwest Himalayas, Pakistan

Abstract

Numerical modeling of Cenozoic compressional events of NW Himalayas, Pakistan is presented. Our goal is to reconstruct stress evolution along major thrusts belonging to the two areas including metamorphic/igneous and sedimentary region. Considering the specific geometry of our problem and the available data at hand, a 2-D thin-plate approach was adopted, assuming plane strain conditions. In the model linear elasticity was used and contact elements were introduced to simulate major faults. Variations in material properties and major thrusts were introduced into the model. For this purpose, we used FEM (ANSYS^TM academic license) to simulate stress and fault slip patterns. We assumed N-S directed regional source of stress associated with collision of Eurasian and Indian Plate. The PT (Panjal Thrust) and its inferred continuation into the Lesser Himalayan Sedimentary Zone form the major mechanical discontinuity in the model. Our results show that the PT (Panjal Thrust) divides the study area into two different stress provinces: the metamorphic/igneous (Higher/Lesser Himalayan Metamorphic Zone) and the sedimentary region (Lesser Himalayan Sedimentary Zone and Sub Himalaya). Compressive structures are observed along all major thrusts including MKT (Main Karakoram Thrust), MMT (Main Mantle Thrust), MCT (Main Central Thrust), PT (Panjal Thrust), MBT (Main Boundary Thrust) and SRT (Salt Range Thrust). The restored stress patterns in NW Himalayas also agree well with the observed present‐day stress configuration. Our analyses also suggest significant strike-slip movement along Jhelum Fault (Left Lateral) and Kalabagh Fault (Right Lateral) where maximum principle stress (σhmax) aligned itself along the strike of the faults. Stress pattern associated with strike-slip movement also to be expected to occur along some segments of major thrusts.

AAPG Datapages/Search and Discovery Article #90350 © 2019 AAPG Annual Convention and Exhibition, San Antonio, Texas, May 19-22, 2019