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Speleothem evidence for Holocene fluctuations of the prairie-forest ecotone, north-central USA
Department of Geology, University of Iowa, Iowa City, Iowa 52242, USA
Department of Earth and Planetary Science, University of New Mexico, Albuquerque, New Mexico 87131, USA
Department of Geology, University of Iowa, Iowa City, Iowa 52242, USA
Department of Geology and Geophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA Carbon and oxygen isotopic trends from seven Midwestern speleothems record significant offsets in the timing of middle-Holocene vegetation change. Interactions of dry Pacific and moist Gulf of Mexico air masses maintained a sharp moisture gradient across Iowa, Minnesota, and Wisconsin such that the arrival of prairie was offset by 2000 years between caves and pollen sites located only 50 km apart. Oxygen isotopes shift concomitantly with carbon in most cases, although these changes are believed to represent increased evaporative enrichment of 18O prior to infiltration during the prairie period.
Key Words: Speleothems oxygen isotopes carbon isotopes climatic change vegetation change prairie-forestecotone Holocene Midwestern USA
The Holocene, Vol. 9, No. 6,
671-676 (1999) This article has been cited by other articles:
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