A geomagnetic excursion/event at similar to 20,000-19,000 years BP recorded from the palaeolake sediments of pithoragarh and Champawat districts, Uttaranchal

摘要

Episodic tectonic disturbances during Late Quaternary period in the Kumaun Himalaya have led to the reactivation of the thrusts/faults in the zones of major intracrustal boundary thrusts thereby blocking the ancient drainage and resulting in formation of lakes. Such tectonic lakes were drained out due to further tectonic disturbances leaving behind their sedimentary records. In such two palaeolake profiles, one at Champawat district (Phulara and Chauki sections) and the other at Pithoragarh district (Riyasi section) of the Uttaranchal state in Kumaun Lesser Himalayas, a reversal (geomagnetic excursion) is recorded at 20,900-19,100 yrs BP. The reversal is found at both the places at the same time though being separated by an aerial distance of about 30 km and being parts of two different palaeolake systems placed in two different tectonic setups. Such excursions have been previously reported in the Kumaun Himalayas (Kotlia et al. 1998) as well as NW Himalaya (Sangode et al. 2002).