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| Titel |
An open ocean record of the Toarcian oceanic anoxic event |
| VerfasserIn |
D. R. Gröcke, R. S. Hori, J. Trabucho-Alexandre, D. B. Kemp, L. Schwark |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1869-9510
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| Digitales Dokument |
URL |
| Erschienen |
In: Solid Earth ; 2, no. 2 ; Nr. 2, no. 2 (2011-11-11), S.245-257 |
| Datensatznummer |
250000597
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| Publikation (Nr.) |
 copernicus.org/se-2-245-2011.pdf |
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| Zusammenfassung |
| Oceanic anoxic events were time intervals in the Mesozoic characterized by
widespread distribution of marine organic matter-rich sediments (black
shales) and significant perturbations in the global carbon cycle. These
perturbations are globally recorded in sediments as carbon isotope
excursions irrespective of lithology and depositional environment. During
the early Toarcian, black shales were deposited on the epi- and
pericontinental shelves of Pangaea, and these sedimentary rocks are
associated with a pronounced (ca. 7 ‰) negative (organic) carbon isotope
excursion (CIE) which is thought to be the result of a major perturbation in
the global carbon cycle. For this reason, the lower Toarcian is thought to
represent an oceanic anoxic event (the T-OAE). If the T-OAE was indeed a
global event, an isotopic expression of this event should be found beyond
the epi- and pericontinental Pangaean localities. To address this issue, the
carbon isotope composition of organic matter (δ13Corg of
lower Toarcian organic matter-rich cherts from Japan, deposited in the open
Panthalassa Ocean, was analysed. The results show the presence of a major
(>6 ‰) negative excursion in δ13Corg that, based on
radiolarian biostratigraphy, is a correlative of the lower Toarcian negative
CIE known from Pangaean epi- and pericontinental strata. A smaller negative
excursion in δ13Corg (ca. 2 ‰) is recognized lower in the
studied succession. This excursion may, within the current
biostratigraphic resolution, represent the excursion recorded in European
epicontinental successions close to the Pliensbachian/Toarcian boundary.
These results from the open ocean realm suggest, in conjunction with other
previously published datasets, that these Early Jurassic carbon cycle
perturbations affected the active global reservoirs of the exchangeable
carbon cycle (deep marine, shallow marine, atmospheric). |
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