The Analysis of The Glaciolacustrine Sediments of Lake Caserococha, Peru
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Date
1985
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The Ohio State University
Abstract
Glaciolacustrine sediments are ideally-suited for paleoclimatic studies because these sediments are deposited continuously in freshwater lakes of glacial origin, and usually remain undisturbed for many thousands of years. Previous studies of elastic sediments as recorders of glaciated and ice-free conditions have been limited to middle and high latitudes. This investigation interprets the paleoclimatic record preserved in the elastic sediments of a low latitude proglacial lake, Lake Caserococha, Peru.
The glaciolacustrine sediments of Lake Caserococha can be divided into three distinct lithologic sections: an upper, homogeneous, organic-rich section; a middle, banded section of clays and silts; and a lower inorganic section of till, including particles of all sizes.
Using visual examination of the core, smear slide sampling and analysis, and X-ray diffraction sampling and analysis, it is possible to observe various changes in sediment characteristics downcore. These changes suggest that the boundary between the lower till section and the middle banded section probably marks the time when the ice receded from the lake. However, the ice remained nearby within the lake's drainage basin, and controlled the sediment deposition of the lake for an additional period in which the banded section was deposited. The boundary between the middle, banded section and the upper, homogeneous section marks the time when there was a loss of major nearby glacial input. This change in lithologies from ice-controlled deposition to deposition that is not ice-controlled suggests the date of deglaciation of the region surrounding Lake Caserococha to be approximately 12,000 y.b.p.
The laminae of the banded section located between 290 cm and 500 cm downcore, suggest the presence of seasonal varves, each with inverse proportions of clay to biogenic abundance; however, a few of the laminae may represent storm deposits.