TY  - JOUR
A1  - Bentum, Elisabeth C. van
A1  - Reichart, Gert-Jan
A1  - Forster, Astrid
A1  - Sinninghe Damsté, Jacobus S.
T1  - Latitudinal differences in the amplitude of the OAE-2 carbon isotopic excursion: pCO2 and paleoproductivity [Discussion paper]
T2  - Biogeosciences discussions
N2  - 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.
Y1  - 2011
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/23492
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-234924
SN  - 1810-6277
N1  - © Author(s) 2011. CC Attribution 3.0 License.
VL  - 8
SP  - 6191
EP  - 6226
PB  - European Geosciences Union
CY  - Katlenburg-Lindau
ER  -