التفاصيل البيبلوغرافية
| العنوان: |
Latitudinal differences in the amplitude of the OAE-2 carbon isotopic excursion: pCO2 and paleo productivity. |
| المؤلفون: |
van Bentum, E. C., Reichart, G.-J., Forster, A., Damsté, J. S. Sinninghe |
| المصدر: |
Biogeosciences; 2012, Vol. 9 Issue 2, p717-731, 15p, 1 Diagram, 1 Chart, 7 Graphs, 1 Map |
| مصطلحات موضوعية: |
CARBON isotopes, CARBON dioxide analysis, PHOTOSYNTHETIC bacteria, BIOMARKERS, OCEAN temperature |
| مصطلحات جغرافية: |
NORTH Atlantic Ocean |
| مستخلص: |
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. [ABSTRACT FROM AUTHOR] |
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| قاعدة البيانات: |
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