Latitudinal differences in the amplitude of the OAE-2 carbon isotopic excursion: pCO2 and paleoproductivity [Discussion paper]
- A complete, well-preserved record of the Cenomanian/Turonian (C/T) Oceanic Anoxic Event 2 (OAE-2) was recovered from Demerara Rise in the southern North Atlantic Ocean (ODP site 1260). Across this interval, we determined changes in the stable carbon isotopic composition of sulfur-bound phytane (δ13Cphytane, a biomarker for photosynthetic algae. The δ13Cphytane record shows a positive excursion at the onset of the OAE-2 interval, with an unusually large amplitude (~7 ‰) compared to existing C/T proto-North Atlantic δ13Cphytane records (3–6 ‰). Overall, the amplitude of the excursion of δ13Cphytane decreases with latitude. Using reconstructed sea surface temperature (SST) gradients for the proto-North Atlantic, we investigated environmental factors influencing the latitudinal δ13Cphytane gradient. The observed gradient is best explained by high productivity at DSDP Site 367 and Tarfaya basin before OAE-2, which changed in overall high productivity throughout the proto-North Atlantic during OAE-2. During OAE-2, productivity at site 1260 and 603B was thus more comparable to the mid-latitude sites. Using these constraints as well as the SST and δ13Cphytane-records from Site 1260, we subsequently reconstructed pCO2 levels across the OAE-2 interval. Accordingly, pCO2 decreased from ca. 1750 to 900 ppm during OAE-2, consistent with enhanced organic matter burial resulting in lowering pCO2. Whereas the onset of OAE-2 coincided with increased pCO2, in line with a volcanic trigger for this event, the observed cooling within OAE-2 probably resulted from CO2 sequestration in black shales outcompeting CO2 input into the atmosphere. Together these results show that the ice-free Cretaceous world was sensitive to changes in pCO2 related to perturbations of the global carbon cycle.
Author: | Elisabeth C. van Bentum, Gert-Jan Reichart, Astrid Forster, Jacobus S. Sinninghe DamstéORCiDGND |
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URN: | urn:nbn:de:hebis:30:3-234924 |
DOI: | https://doi.org/10.5194/bgd-8-6191-2011 |
ISSN: | 1810-6277 |
Parent Title (English): | Biogeosciences discussions |
Publisher: | European Geosciences Union |
Place of publication: | Katlenburg-Lindau |
Document Type: | Article |
Language: | English |
Date of Publication (online): | 2011/06/30 |
Date of first Publication: | 2011/06/30 |
Publishing Institution: | Universitätsbibliothek Johann Christian Senckenberg |
Release Date: | 2011/12/06 |
Volume: | 8 |
Page Number: | 18 |
First Page: | 6191 |
Last Page: | 6226 |
Note: | © Author(s) 2011. CC Attribution 3.0 License. |
HeBIS-PPN: | 286887207 |
Institutes: | Geowissenschaften / Geographie / Geowissenschaften |
Dewey Decimal Classification: | 5 Naturwissenschaften und Mathematik / 55 Geowissenschaften, Geologie / 550 Geowissenschaften |
Sammlungen: | Universitätspublikationen |
Licence (German): | Creative Commons - Namensnennung 3.0 |