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Letter
Nature 277, 375-377 (1 February 1979) | doi:10.1038/277375a0; Accepted 5 December 1978
Glaciation in Bolivia before 3.27 Myr
C. M. CLAPPERTON
Abstract
AN in situ layer of ignimbrite overlies till near the base of a thick sequence of glacial and fluvioglacial sediments at La Paz, Bolivia. Two radiogenic age determinantions on the ignimbrite gave results of 3.27
0.14 and 3.280.13 Myr. We show here that this indicates that climatic cooling in the Southern Hemisphere was sufficiently severe to produce a mountain ice cap over part of the tropical Andes before 3.27 Myr and that these mountains had probably become tectonically elevated to about their present altitude by that time.
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