Climate and seismicity in the higher Central Himalaya during 20–10 ka: evidence from the Garbayang basin, Uttaranchal, India

In the Trans-Himalaya, the Trans-Himadri fault (THF) controlled the extent of past glaciers. The rivers were impounded by glacial debris resulting in the formation of lakes that recorded regional climatic and seismic events. One such lake formed at Garbayang, where the upper 28 m lacustrine succession spanned an age range of 20–10 ka. Magnetic susceptibility and sedimentological data suggest that the region experienced high amplitude low frequency millennial scale climate changes during the period 20±3 and 13±2 ka followed by low amplitude high frequency changes from 13±2–11±1 ka. A sudden drop in magnetic susceptibility and elemental concentration of layers dated at ∼11–12 ka suggests cooling associated with the Younger Dryas. Occurrence of faulted strata/seismites during 20–17 and 14–13 ka suggests recent activation of the THF. This is noteworthy, as the THF has been considered dormant since its last reactivation at 11 Ma. Further, the luminescence dates suggest that radiocarbon ages on organic carbon are grossly overestimated due to a hard water effect caused by the dominance of limestone in the lake catchment. This implies that earlier, radiocarbon based palaeoenvironmental reconstruction in the region, will need revalidation.