| Title: | Carbon isotopic variation in woody, lacustrine, and marine organic matter as records of source and concentration of atmospheric CO2 through the Cretaceous |
| Author: | Lisa M. Pratt |
| Date Submitted: | 05/01/2002 |
| Address: | 1001 East 10th Street
Bloomington
Indiana
U.S.A.
47405
|
| Phone: | 812-855-9203 |
| Email: | prattl@indiana.edu |
| Co-Authors: | Hasegawa, Takashi, Kanazawa University; Finkelstein, David, Indiana University |
| Affiliation: | Indiana University |
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| Abstract URL: | http://cis.whoi.edu/science/GG/ccod/viewAbstracts.cfm?RefNumber=19725598 |
| Keywords: | carbon isotope, organic matter, atmospheric CO2 |
| Abstract: | Carbon isotopic research on Cretaceous organic matter has focused on three major facies: terrestrial woody, lacustrine algal/bacterial and marine algal. The least studied of the three being lacustrine systems. Detailed carbon-isotope stratigraphies have been published for marine organic in pelagic marine sections from many continental and oceanic localities. Deviating trends in isotopic values for carbonate compared to woody or marine organic matter at critical intervals in coeval sections can be interpreted in terms of elevated concentration of atmospheric CO2 with a volcanic source and an isotopic composition of about -7 per mil. Stratigraphic uncoupling of these isotopic records results from concentration-dependent photosynthetic fractionation for organic matter compared to concentration-independent precipitation fractionation for most carbonates. Deviating trends in isotopic values for woody compared to marine algal organic matter are expected under terrestrial climatic conditions that amplify the anatomical differences between leaves in high plant leaves and cells, filaments or blades in algae. Cretaceous lacustrine strata have been largely ignored from the perspective of carbon isotope stratigraphy and systematics. Research currently in progress on Cretaceous lakes and wetlands from the southwestern margin of the U.S. Western Interior seaway suggests wildfires and bacterial blooms as important factors in the carbon-isotopic stratigraphy for lacustrine facies. |
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