Radiometric chronology of Changme-Khangpu glacier, Sikkim

• Main Authors: Nijampur, V. N., Bhandari, N., Borole, D. V., Bhattacharya, U.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: International Glaciological Society 1985
• Subjects: QB Astronomy; Journal of Glaciology
• Online Access: http://repository.ias.ac.in/18494/; http://repository.ias.ac.in/18494/1/355.pdf; http://www.igsoc.org/journal/31/107/igs_journal_vol31_issue107_pg28-33.pdf

The 32 Si concentration in a sample of surface ice from the snout of Changme-Khangpu glacier is 0.36 disintegrations per minute/tonne compared to the fall-out value of 0.7 d.p.m./tonne. If this decrease is assumed to be solely due to decay of 32 Si, an age of c. 100 years is estimated for the surface ice of the snout, leading to an average flow velocity of c. 40 m/year for the past century. A vertical profile of 210 Pb in a core taken at an altitude of 5040 m shows two horizons where this isotope is enriched, one between 3 and 4 m and another between I I and 12 m, indicating that the primary concentration of 2l0 Pb can change by physicochemical processes like adsorption on dust. None the less, a longitudinal profile along the glacier shows a systematic decrease of 2l0 Pb activity with decreasing altitude, the surface ice of the snout giving a value of 0.2 d.p.m./I, corresponding to an age of 100 years which is concordant with the 32 Si age. This surface flow-rate of the glacier is much larger than the average contemporary flow-rate (c. 13 m/year). The difference can be understood of the past history of advance and recession of the glacier as revealed by the geomorphic evidence.