Details
| Original language | English |
|---|---|
| Pages (from-to) | 303-318 |
| Number of pages | 16 |
| Journal | Earth and Planetary Science Letters |
| Volume | 223 |
| Issue number | 3-4 |
| Publication status | Published - 15 Jul 2004 |
| Externally published | Yes |
Abstract
The deposition of organic-rich sediments during the late Early Aptian Oceanic Anoxic Event (OAE) 1a has been interpreted to result in a major decrease of palaeoatmospheric CO2 concentrations, accompanied by significant changes in the terrestrial flora. In order to test this hypothesis, the OAE 1a interval in the Vocontian Basin (SE France) has been studied with a combined approach including stable carbon isotopes, organic geochemistry and palynology. To estimate changes in palaeoatmospheric CO2 levels across the OAE 1a, the δ 13C composition of presumed algal biomarkers (low molecular weight n -alkanes, steranes) and of bulk carbonate carbon are used. Our results yield estimated Early Aptian carbon dioxide partial pressure (pCO2) values three to four times the preindustrial level and only a moderate drop across the black shale event. This moderate drop in pCO2 is supported by palynological results. The frequency patterns of climate-sensitive sporomorphs (incl. pteridophyte spores, bisaccate pollen and Classopollis spp.) display only minor fluctuations throughout the studied section and indicate relatively stable patterns of terrestrial vegetation during and after formation of the OAE 1a black shale. The occurrence of a characteristic Early Aptian carbon isotope pattern across the OAE 1a interval permits accurate chemostratigraphic correlation with the well-studied Livello Selli interval of the Cismon record (N Italy). The contemporaneous formation of individual black shale layers at both sites indicates that transient episodes of dysoxic-anoxic bottom waters prevailed over large areas in the W Tethys Ocean independent of depositional setting. Comparison of the palynological data from the two locations displays significant differences in the frequency patterns of bisaccate pollen. The contrasting pollen spectra are interpreted to reflect prominent changes in the palaeoceanographic current patterns and/or selective sorting due to sea-level rise rather than latitudinal shifts of the major floral belts.
Keywords
- Aptian, Black shale, Carbon isotope, Early Cretaceous, OAE, Organic geochemistry, Palaeoatmosphere, Palynology
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Geophysics
- Earth and Planetary Sciences(all)
- Geochemistry and Petrology
- Earth and Planetary Sciences(all)
- Earth and Planetary Sciences (miscellaneous)
- Earth and Planetary Sciences(all)
- Space and Planetary Science
Sustainable Development Goals
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In: Earth and Planetary Science Letters, Vol. 223, No. 3-4, 15.07.2004, p. 303-318.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Absence of major vegetation and palaeoatmospheric pCO2 changes associated with oceanic anoxic event 1a (Early Aptian, SE France)
AU - Heimhofer, Ulrich
AU - Hochuli, Peter A.
AU - Herrle, Jens O.
AU - Andersen, Nils
AU - Weissert, Helmut
N1 - Funding Information: We thank Luc Zwank from the EAWAG for support with the irmGC-MS measurements and Christian Ostertag-Henning from the University of Münster for the help with the sterane identification. This manuscript was significantly improved thanks to the suggestions and reviews by R.V. Tyson and M. Pagani. Financial support from ETH-project TH-34./99-4 is greatfully acknowledged. [BARD]
PY - 2004/7/15
Y1 - 2004/7/15
N2 - The deposition of organic-rich sediments during the late Early Aptian Oceanic Anoxic Event (OAE) 1a has been interpreted to result in a major decrease of palaeoatmospheric CO2 concentrations, accompanied by significant changes in the terrestrial flora. In order to test this hypothesis, the OAE 1a interval in the Vocontian Basin (SE France) has been studied with a combined approach including stable carbon isotopes, organic geochemistry and palynology. To estimate changes in palaeoatmospheric CO2 levels across the OAE 1a, the δ 13C composition of presumed algal biomarkers (low molecular weight n -alkanes, steranes) and of bulk carbonate carbon are used. Our results yield estimated Early Aptian carbon dioxide partial pressure (pCO2) values three to four times the preindustrial level and only a moderate drop across the black shale event. This moderate drop in pCO2 is supported by palynological results. The frequency patterns of climate-sensitive sporomorphs (incl. pteridophyte spores, bisaccate pollen and Classopollis spp.) display only minor fluctuations throughout the studied section and indicate relatively stable patterns of terrestrial vegetation during and after formation of the OAE 1a black shale. The occurrence of a characteristic Early Aptian carbon isotope pattern across the OAE 1a interval permits accurate chemostratigraphic correlation with the well-studied Livello Selli interval of the Cismon record (N Italy). The contemporaneous formation of individual black shale layers at both sites indicates that transient episodes of dysoxic-anoxic bottom waters prevailed over large areas in the W Tethys Ocean independent of depositional setting. Comparison of the palynological data from the two locations displays significant differences in the frequency patterns of bisaccate pollen. The contrasting pollen spectra are interpreted to reflect prominent changes in the palaeoceanographic current patterns and/or selective sorting due to sea-level rise rather than latitudinal shifts of the major floral belts.
AB - The deposition of organic-rich sediments during the late Early Aptian Oceanic Anoxic Event (OAE) 1a has been interpreted to result in a major decrease of palaeoatmospheric CO2 concentrations, accompanied by significant changes in the terrestrial flora. In order to test this hypothesis, the OAE 1a interval in the Vocontian Basin (SE France) has been studied with a combined approach including stable carbon isotopes, organic geochemistry and palynology. To estimate changes in palaeoatmospheric CO2 levels across the OAE 1a, the δ 13C composition of presumed algal biomarkers (low molecular weight n -alkanes, steranes) and of bulk carbonate carbon are used. Our results yield estimated Early Aptian carbon dioxide partial pressure (pCO2) values three to four times the preindustrial level and only a moderate drop across the black shale event. This moderate drop in pCO2 is supported by palynological results. The frequency patterns of climate-sensitive sporomorphs (incl. pteridophyte spores, bisaccate pollen and Classopollis spp.) display only minor fluctuations throughout the studied section and indicate relatively stable patterns of terrestrial vegetation during and after formation of the OAE 1a black shale. The occurrence of a characteristic Early Aptian carbon isotope pattern across the OAE 1a interval permits accurate chemostratigraphic correlation with the well-studied Livello Selli interval of the Cismon record (N Italy). The contemporaneous formation of individual black shale layers at both sites indicates that transient episodes of dysoxic-anoxic bottom waters prevailed over large areas in the W Tethys Ocean independent of depositional setting. Comparison of the palynological data from the two locations displays significant differences in the frequency patterns of bisaccate pollen. The contrasting pollen spectra are interpreted to reflect prominent changes in the palaeoceanographic current patterns and/or selective sorting due to sea-level rise rather than latitudinal shifts of the major floral belts.
KW - Aptian
KW - Black shale
KW - Carbon isotope
KW - Early Cretaceous
KW - OAE
KW - Organic geochemistry
KW - Palaeoatmosphere
KW - Palynology
UR - http://www.scopus.com/inward/record.url?scp=3042771875&partnerID=8YFLogxK
U2 - 10.1016/j.epsl.2004.04.037
DO - 10.1016/j.epsl.2004.04.037
M3 - Article
AN - SCOPUS:3042771875
VL - 223
SP - 303
EP - 318
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
SN - 0012-821X
IS - 3-4
ER -