Radiometric chronology of Neh-Nar Glacier, Kashmir

Abstract

Surface and core samples of Neh-nar Glacier in the Kashmir Valley have been analysed for the radionuclides ³²Si, ^2lOpb, ⁴⁰K, and ¹³⁷Cs. The lateral and vertical profiles (at an altitude of about 4 140 m) reveal: ( I ) ³²Si activity decreasing slowly from the accumulation zone to 4 050 m altitude and then abruptly towards the snout. (2) Five zones of alternating high and low ^2lOPb activity in the surface samples. (3) An horizon at between 2 and 3 m depth containing ²¹⁰Pb activity above natural levels. This horizon is also associated with ^1l7Cs and a maximum in total β activity. The ice sam.les have been dated on the basis of a simplified two-component model, the "fresh" contribution determined by ^21OPb and the old component by ³²Si. The following conclusions can be drawn from these observations: (I) The model age of the snout ice is c. 850 years. (2) The average rate of ice movement in the lower glacier is about 2 m/year, which compares well with the annual movement rate of 2.65 m/year observed since 1974.