Geochemistry of brachiopods: oxygen and carbon isotopic records of paleozoic oceans

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6070760

Veizer, J; Fritz, P; Jones, B

Combined trace element and isotope studies of 319 brachiopods, covering the Ordovician to Permian time span, show that delta/sup 13/C and delta/sup 18/O in well preserved specimens varied in the course of the Paleozoic. The overall delta/sup 13/C secular trend is in accord with the previously published observations, but its details are obscured by vital isotopic fractionation effects at generic levels. Nonetheless, the results suggest that the negative correlation between delta/sup 13/C/sub carbonate/ and delta/sup 34/S/sub sulfate/ deteriorates on time scales of less than or equal to 10/sup 6/ years, due to the long residence time, and thus slow response, of SO/sub 4//sup 2 -/ in the ocean. For oxygen isotopes, all Devonian and older specimens have delta/sup 18/O of less than or equal to -4 percent per thousand, while the well preserved Permian samples have near-present day delta/sup 18/O of about -1 percent per thousand (PDB). This isotopic dichotomy is unlikely a consequence of post-depositional phenomena, salinity, or biogenic fractionation effects. This leaves open the perennial argument for a change in /sup 18/O//sup 16/O of sea water vs warmer ancient oceans. The present data are difficult to explain solely by the temperature alternative. In contrast, the coincidence of the proposed shift in delta/sup 18/O with the large Late Paleozoic changes in marine /sup 87/Sr//sup 86/Sr, /sup 13/C//sup 12/C, /sup 34/S//sup 32/S, and sea level stands argues for a tectonic cause and for a change in /sup 18/O//sup 16/O of sea water. Whatever the precise cause, or combination of causes, the implications for tectonism and/or paleoclimatology are of first order significance.

• Research Organization: Univ. of Ottawa, Ontario (Canada)
• OSTI ID: 6070760
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580100* -- Geology & Hydrology-- (-1989)
580400 -- Geochemistry-- (-1989)
580500 -- Oceanography-- (1980-1989)
ANIMALS
AQUATIC ORGANISMS
CARBON ISOTOPES
CHEMICAL COMPOSITION
CHEMISTRY
GEOCHEMISTRY
GEOLOGIC AGES
HYDROGEN COMPOUNDS
INVERTEBRATES
ISOTOPE RATIO
ISOTOPES
MOLLUSCS
OCEANOGRAPHY
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
PALEOCLIMATOLOGY
PALEONTOLOGY
PALEOZOIC ERA
SEAWATER
VARIATIONS
WATER
WATER CHEMISTRY