Radiometric Chronology of Changme-Khangpu Glacier Sikkim
Abstract 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 off c . 100 years is estimated for...
| Published in: | Journal of Glaciology |
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| Main Authors: | , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Cambridge University Press (CUP)
1985
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.1017/s0022143000004950 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000004950 |
| Summary: | Abstract 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 off 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 11 and 12 m, indicating that the primary concentration of 210 Pb can change by physico-chemical processes like adsorption on dust. None the less, a longitudinal profile along the glacier shows a systematic decrease of 210 Pb activity with decreasing altitude, the surface ice of the snout giving a value of 0.2 d.p.m./l, 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. 13m/year). The difference can be understood in terms of the past history of advance and recession of the glacier as revealed by the geomorphic evidence. |
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