| Title: | Cretaceous terrestrial paleoenvironments of northeastern Asia suggested from carbon isotope stratigraphy: increased atmospheric pCO2-induced climate |
| Author: | Takashi Hasegawa |
| Date Submitted: | 04/28/2002 |
| Address: | Dept. Earth Science, Fac. Science, Kanazawa Univ.
Kakuma-machi
Kanazawa
Ishikawa
Japan
920-1192
|
| Phone: | +81-76-264-5636 |
| Email: | jh7ujr@kenroku.kanazawa-u.ac.jp |
| Co-Authors: | |
| Affiliation: | Dept. Earth Science, Faculty of Science, Kanazawa |
| | |
| Abstract URL: | http://cis.whoi.edu/science/GG/ccod/viewAbstracts.cfm?RefNumber=19725502 |
| Keywords: | terrestrial, paleoenvironment, pCO2, carbon, isotope, Asia |
| Abstract: | Terrestrial organic carbon from Cenomanian - Turonian sequences
in Hokkaido Island, Japan has retained an isotopic record of the
response of terrestrial higher plants to the paleoenvironment,
superimposed on carbon isotope ratio fluctuation of atmospheric
CO2. The stratigraphic record of organic carbon
isotopic compositions from the Hokkaido sections has been
correlated to the carbonate carbon isotope record from Europe and
North America; however, considerable discrepancy in the long-
term, time-stratigraphic pattern of these isotope ratio curves
exists through the Middle-Upper Cenomanian and Lower Turonian.
Contrary to the marine carbonate profiles from Europe and North
America which show consistent, positive migration through the
Upper Cenomanian, terrestrial organic carbon isotope values
display a negative shift through the Upper Cenomanian followed by
positive recovery in the Lower Turonian. Environmental pressures
that only affected carbon isotope values of terrestrial organic
carbon but not those of carbonate carbon are causal factors for
this discrepancy. Variations in atmospheric temperature and
humidity, and related conditions of carbon cycling in forests, may
have acted as factors to shift isotope values of terrestrial organic
carbon negatively. This causal relationship between climate and
carbon isotope ratio fractionation is best explained when an
increasing atmosperic pCO2, which is suggested from a
decoupling between isotope ratio curves of marine organic carbon
and carbonate, is understood as a driving force for a climatic
optimum during the Middle Cenomanian through Early Turonian. |
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