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D/H ratios in speleothem fluid inclusions: A guide to variations in the isotopic composition of meteoric precipitation?

R.S. Harmon·H.P. Schwarcz·J. R. O’Neil
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Abstract

D/H ratios of fluid inclusion waters extracted from 230 Th/ 234 U-dated speleothems that were originally deposited under conditions of isotopic equilibrium should provide a direct estimate of the hydrogen isotopic composition of ancient meteoric waters. We present here D/H ratios for 47 fluid inclusion samples from thirteen speleothems deposited over the past 250,000 years at cave sites in Iowa, West Virginia, Kentucky and Missouri. At each site glacial-age waters are depleted in deuterium relative to those of interglacial age. The average interglacial/glacial shift in the hydrogen isotopic composition of meteoric precipitation over ice-free areas of east-central North America is estimated to be −12‰. This shift is consistent with the present climatic models and can be explained in terms of the prevailing pattern of atmospheric circulation and an increased ocean-continent temperature gradient during glacial times which more than compensated for the increase in deuterium content of the world ocean.

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R.S. Harmon, H.P. Schwarcz, J. R. O’Neil. 1979. D/H ratios in speleothem fluid inclusions: A guide to variations in the isotopic composition of meteoric precipitation?. https://doi.org/10.1016/0012-821x(79)90033-5

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