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The implication of the oxygen isotope records in coexisting cherts and phosphates

Karhu, J. and Epstein, S. (1986) The implication of the oxygen isotope records in coexisting cherts and phosphates. Geochimica et Cosmochimica Acta, 50 (8). pp. 1745-1756. ISSN 0016-7037. doi:10.1016/0016-7037(86)90136-5.

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δ¹⁸O values have been determined for 53 coexisting chert-phosphate pairs from the Phanerozoic and Precambrian. In addition, δ¹⁸O values were also determined for 18 biogenic phosphates from the Phanerozoic. The oxygen isotope data for the chert-phosphate pairs permit the calculation of the temperatures of formation of the chert-phosphate pairs as well as the δ^(18)O of the waters in which they equilibrated. In turn the calculated δ¹⁸O of the waters permit the calculation of temperatures from the isotopic data of the biogenic phosphates. The temperatures for the Tertiary and Mesozoic samples are compatible with the literature values determined from oxygen isotope data for well-preserved calcareous marine skeletal remains. The temperatures calculated from the chert-phosphate pairs of the Paleozoic are usually higher and vary in cycles of about a 150 million year period. The early Precambrian temperatures are as high as 80°C and decrease with time. The use of chert-phosphate pairs for temperature determinations are sufficiently promising to warrant further investigations of this type on well preserved chert-phosphate or carbonate-phosphate pairs.

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Additional Information:© 1986 Pergamon Journals Ltd. Received August 14, 1985; accepted in revised form May 14, 1986. We thank David Kennedy, L. P. Knauth, Y. Kolodny, A. Knoll, H. A. Lowenstam, J. W. Schopf, H. F. Shaw, E. C. Wilson, and J. Wright for generously contributing samples and critical information about them and for helpful discussions. We thank M. Baumer, J. Goris, L. Herkenhoff, and J. Ruth for assistance in the laboratory. The Geological Survey of Finland and the Academy of Finland provided a major proportion of the salary for one of us (J.K.). This work was supported by the N.S.F. Grant No. EAR 8313086.
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Geological Survey of FinlandUNSPECIFIED
Academy of FinlandUNSPECIFIED
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Caltech Division of Geological and Planetary Sciences4247
Issue or Number:8
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Official Citation:J. Karhu, S. Epstein, The implication of the oxygen isotope records in coexisting cherts and phosphates, Geochimica et Cosmochimica Acta, Volume 50, Issue 8, August 1986, Pages 1745-1756, ISSN 0016-7037,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:41451
Deposited By: Tony Diaz
Deposited On:20 Sep 2013 21:08
Last Modified:15 Aug 2022 17:49

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