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| Titel |
Freshwater discharge controlled deposition of Cenomanian–Turonian black shales on the NW European epicontinental shelf (Wunstorf, northern Germany) |
| VerfasserIn |
N. A. G. M. van Helmond, A. Sluijs, J. S. Sinninghe Damsté, G.-J. Reichart, S. Voigt, J. Erbacher, J. Pross, H. Brinkhuis |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 11, no. 3 ; Nr. 11, no. 3 (2015-03-18), S.495-508 |
| Datensatznummer |
250117211
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| Publikation (Nr.) |
 copernicus.org/cp-11-495-2015.pdf |
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| Zusammenfassung |
Global warming, changes in the hydrological cycle and enhanced marine primary
productivity all have been invoked as having contributed to the occurrence of
widespread ocean anoxia during the Cenomanian–Turonian oceanic anoxic event
(OAE2; ~94 Ma), but disentangling these factors on a regional scale
has remained problematic. In an attempt to separate these forcing factors, we
generated palynological and organic geochemical records using a core spanning
the OAE2 from Wunstorf, Lower Saxony Basin (LSB; northern Germany), which
exhibits cyclic black shale–marl alternations related to the orbital
precession cycle.
Despite the widely varying depositional conditions complicating the
interpretation of the obtained records, TEX86H indicates that
sea-surface temperature (SST) evolution in the LSB during OAE2 resembles that
of previously studied sites throughout the proto-North Atlantic. Cooling
during the so-called Plenus Cold Event interrupted black shale deposition
during the early stages of OAE2. However, TEX86 does not vary
significantly across black shale–marl alternations, suggesting that
temperature variations did not force the formation of the cyclic black shale
horizons. Relative (i.e., with respect to marine palynomorphs) and absolute
abundances of pollen and spores are elevated during phases of black shale
deposition, indicative of enhanced precipitation and run-off. High abundances
of cysts from inferred heterotrophic and euryhaline dinoflagellates supports
high run-off, which likely introduced additional nutrients to the
epicontinental shelf resulting in elevated marine primary productivity.
We conclude that orbitally forced enhanced precipitation and run-off, in
tandem with elevated marine primary productivity, were critical in cyclic
black shale formation on the northern European epicontinental shelf and
potentially for other OAE2 sections in the proto-Atlantic and Western
Interior Seaway at similar latitudes as well. |
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