Abstract
Carbon isotope compositions (δ13C) of inarticulate brachiopod shells from Upper Cambrian sandstone in the cratonic interior of Laurentia record a 5‰ positive excursion that correlates biostratigraphically with the global Steptoean positive isotopic carbon excursion. A consistent 6‰ negative displacement in brachiopod δ13C relative to carbonate values is interpreted to represent an onshore-offshore gradient in the isotopic composition of dissolved inorganic carbon in Cambrian seawater. Thus, these ~500-m.y.-old chitinophosphatic brachiopod shells preserve evidence for carbon cycle coupling between the ancient atmospheric, oceanic, and terrestrial reservoirs in the time before embryophytic land plants.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 661-664 |
| Number of pages | 4 |
| Journal | Geology |
| Volume | 33 |
| Issue number | 8 |
| DOIs | |
| State | Published - 2005 |
Bibliographical note
Funding Information:We thank A.R. Palmer (Institute of Cambrian Studies) for trilobite and brachiopod identifications; David Auerbach, Steve Dworkin, Larry Mack, Sam Matson, Robert McKay, and Maniko Solheid for sampling and laboratory support; and B. Glumac, G. Ludvigson, and I. Montañez for helpful reviews. Strontium isotopes were analyzed at the Department of Geological Sciences, University of Texas at Austin; carbon isotopes were analyzed at the University of Minnesota. Funding was provided by the Henrickson and Potts funds of the Carleton College Geology Department, and by the Minnesota Geological Survey and the University of Minnesota.
Publisher Copyright:
© 2005 Geological Society of America.
Keywords
- Brachiopod
- Cambrian
- Chitinophosphatic
- Inarticulate brachiopod
- δC
