The implication of the oxygen isotopic composition of lower Devonian micritic limestone, Oklahoma

Conference · Wed Jan 01 00:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5931542

Gao, G ^[1]

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1. Univ. of Texas, Austin, TX (United States). Dept. of Geological Sciences

The documented [delta]O-18 values of presumably well preserved lower Devonian marine carbonates are significantly lower than those of post-Devonian carbonates. These have been interpreted to have resulted from either O-18-depleted or hot oceans, relative to post-Devonian oceans. To test these hypotheses, micritic limestones were sampled for oxygen (as well carbon and strontium) isotope analysis from the lower Devonian (Lochkovian) Haragan-Bois d'Arc formations of the Hunton Group, South-Central Oklahoma. Of the 25 analyzed samples, 22 samples are characterized by high [delta]C-13 values and ranging from [minus]1.9[per thousand] to [minus]2.9[per thousand](PDB). These are the highest [delta]C-13 limestones were deposited in a shallow normal marine setting and have both [delta]C-13 values and Sr-87/Sr-86 ratios similar to other lower Devonian carbonates elsewhere, the high [delta]O-18 values of these limestones are unlikely to have originated either from any unusual depositional setting or from diagenetic alteration at low temperatures by O-18- and Sr-87-enriched basinal brines. The high [delta]O-18 values of the Haragan-Bois d'Arc limestones are thus interpreted to represent near-primary signals. The temperatures and [delta]O-18 values of early Devonian seawater can be constrained to have been 25 [+-] 7 C and 0 [+-] 1[per thousand] (SMOW), respectively. This implies that neither O-18 depletion nor high temperatures characterized early Devonian oceans.

• OSTI ID: 5931542
• Report Number(s): CONF-921058-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 24:7; Conference: 1992 annual meeting of the Geological Society of America (GSA), Cincinnati, OH (United States), 26-29 Oct 1992; ISSN 0016-7592
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
LIMESTONE
ISOTOPE RATIO
OKLAHOMA
SEDIMENTARY BASINS
GEOCHEMISTRY
CARBON 13
DEVONIAN PERIOD
ORIGIN
OXYGEN 18
SEAS
STRONTIUM 86
STRONTIUM 87
ALKALINE EARTH ISOTOPES
BETA DECAY RADIOISOTOPES
CARBON ISOTOPES
CARBONATE ROCKS
CHEMISTRY
DEVELOPED COUNTRIES
ELECTRON CAPTURE RADIOISOTOPES
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
GEOLOGIC AGES
GEOLOGIC STRUCTURES
HOURS LIVING RADIOISOTOPES
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
LIGHT NUCLEI
NORTH AMERICA
NUCLEI
OXYGEN ISOTOPES
PALEOZOIC ERA
RADIOISOTOPES
ROCKS
SEDIMENTARY ROCKS
STABLE ISOTOPES
STRONTIUM ISOTOPES
SURFACE WATERS
USA
580000* - Geosciences