Response of 10 Ma thrusting event in the Himalayan Foreland sediments, Kangra sub-basin, Himachal Pradesh, India

Using detrital modes and sedimentation pattern of Late Neogene (11.3-5.5 Ma) coarsening up fluviatile succession of Himalayan foreland (Siwalik) of the Kangra sub-basin, an attempt has been made to understand the interrelationship of source area thrusting and their response in the detrital modes. The sedimentary succession consists of dark grey sandstone interbedded with purple mudstone in lower part, overlain by salt- and pepper grey sandstone and variegated mudstone and capped by thickly bedded conglomerate with minor amount of coarse-grained sandstone and mudstone. The sedimentologic parameters show change in palaeochannel pattern from meandering to braided streams at 10 Ma and inception of alluvial fan settings at around 5.5 Ma. A remarkable variation in detrital modes is also noticed between 10 and 9.0 Ma. The study suggests that prior to 10 Ma due to tectonic activity along the Chail Thrust (CT) the depocenter received high amount of Lesser- and Sub-Himalayan (LHZ and SHZ) footwall sedimentary and metasedimentary fragments. Subsequently, after 10 Ma, the detritus from the Chail Metamorphics Zone (CMZ) forming the hanging wall, became more abundant. The present study infers that the variation in the drainage pattern, sedimentation accumulation rate and detrital modes are collectively pertinent to the 10 Ma tectonic activity of the Chail Thrust.