QUATERNARY GLACIAL HISTORY OF NW GARHWAL, CENTRAL HIMALAYAS

A first account of the Quaternary glacial history is presented for nor thwest Garhwal, Central Himalaya. On the basis of sediments and landfo rms, one glacial stage has been recognised. This is called the Bhagira thi Glacial Stage, when extensive valley glaciers advanced down the Bh agirathi valley to Jhala, 40.5 km from the snout of Gangotri Glacier. The ELA depression during this stage was ca. 640 m. The Bhagirathi Gla cial Stage is constrained by optically stimulated luminescence dates o f ca. 63 ka and 5 ka BP, and this glaciation is considered equivalent to the Last Glaciation elsewhere in the world. The maximum extent of i ce occurred ca. 63 ka BP. This, however, does not correlate with the L ast Glacial Maximum for the northern hemisphere ice sheets (20-18 ka B P). A series of sharp-crested moraines are present between 1 to 3 km b eyond the snouts of most of the present glaciers. These moraines forme d during the mid Holocene (<5 ka BP), termed here the Shivling Glacial Advance. Small moraines are inset into these and are dated at about 2 00 to 300 BP (the Bhujbas Glacial Advance; ca. 300 to 200 BP) and cons idered equivalent to the Little Ice Age in other parts of the world. E LA depressions of between 40-100 m and 20-60 m occurred during the Shi vling and Bhujbas Glacial Advances, respectively. Since the Bhujbas Gl acial Advance, there has been progressive retreat of glaciers, initial ly by downwasting and retreat, and then by simple retreat. This retrea t has accelerated during the last few decades. Impressive paraglacial fans are associated with deglaciation representing very rapid resedime ntation during and soon after ice retreat. Copyright (C) 1996 Elsevier Science Ltd.