Isotopic evidence for late Quaternary climatic change in tropical South America
- 1Department of Earth Sciences, Syracuse University, Syracuse, New York 13244, USA
- 2Department of Geology, Union College, Schenectady, New York 12308, USA
- 3Department of Geology, University of Bern, Switzerland
Abstract
The tropical hydrologic cycle affects atmospheric trace gases and global climate change, and thus records of hydrologic change encompassing a variety of time scales from the low latitudes are important in paleoclimatology. Isotopic analysis of calcite from Lake Junin, Peru, provides a record of hydrologic variability that spans the last glacial-interglacial transition in the southern tropics. The record reveals a 6‰ enrichment in δ18Ocalcite during the late glacial followed by a gradual depletion during the Holocene, which can be interpreted as a decrease followed by a long-term increase in effective moisture. Close agreement between δ18Ocalcite and rainy season insolation indicates that long-term changes in tropical hydrology were linked to orbital variations. Furthermore, hydrologic change was out of phase in the northern and southern tropics over this time period.
Footnotes
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- Accepted August 14, 1999.
- Received May 14, 1999.
- Revision received August 6, 1999.
- Geological Society of America
