Neotectonic and climatic impressions in the zone of Trans Himadri Fault (THF), Kumaun Tethys Himalaya, India: A case study from palaeolake deposits

摘要

Late Quaternary tectonic activity on a NW-SE trending fault within the Trans Himadri Fault (THF) zone in lower reaches of the Milam glacier (Indian Tethys Himalaya) resulted in development of a lake around 23 ka BP. The remnants of the ancient lake are preserved in form of a 25.6 m thick lacustrine profile, consisting of muds and sands. The palaeolake seems to have breached around 11 ka BP possibly due to revival of a further event of neotectonic activity. The geomorphic consequences of the tectonic movements in the fault zone are manifest in form of palaeo-landslide cones, unpaired terraces, fault facets, soaring waterfalls, deep gorges and slope failures etc. The soft sedimentary structures, e. g., micro-faulting and flame structures in the exposed profile also point to a possible reactivation of the THF in the Late Pleistocene. We present the first palynological results from otherwise a totally unexplored area in the eastern part of the Indian Tethys Himalaya. The preliminary results indicate that the area experienced cold desertic climatic conditions from ca. 22.9 to 15.7 ka BP covering a period of Last Glacial Maximum (LGM) and during which the sediment accumulation rate was also extremely slow. This phase was followed by deglaciation together with amelioration of climate between ca. 15.7 and 14.5 ka BP. A dry period from ca. 14.5 to 13.8 ka BP can be associated with the Older Dryas. The area underwent wetter/moist conditions from ca. 13.8 to 12.8 ka BP, followed by a century scale dry event (ca. 12.8 to 12.7 ka BP) which may be linked to the Younger Dryas episode.