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| Titel |
The Cenomanian-Turonian boundary event in the Tethys realm: insights from geochemical and calcareous nannofossil evidences |
| VerfasserIn |
Mihaela Melinte-Dobrinescu, Marcos A. Lamolda, Enrique Bernárdez, Kunio Kaiho |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250055352
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| Zusammenfassung |
| A significant biotic turnover accompanied the deposition of the Oceanic Anoxic Event 2 (OAE2), within the Cenomanian-Turonian boundary interval, mirrored in the diversity and composition of the marine planktonic faunas and floras, especially of foraminifers and calcareous nannofossils (Lamolda et al., 1994; Premoli-Silva et al., 1999; Erba, 2004; Hardas and Mutterlose, 2007). Our investigations focussed on sections from N Spain, a region where the OAE2 is very well expressed (Paul et al., 1994; Lamolda et al., 1997), aiming to extend the knowledge on the geochemical and biotic records of OAE2. The gathered data indicate that blooms of the nannofossil fertility indexes, such as Biscutum constans and Zeugrhabdotus erectus, took place well below the increasing in 13C values that marks the onset of OAE2. The blooms of the above-mentioned nannofossils reflect change in primary productivity of the surface waters, from a mesotrophic setting (prior OAE2) towards an eutrophic setting (at the debut of OAE2), preceding the instauration of an anoxic regime. The blooms of the calcareous dinoflagellate genus Thoracosphaera, observed in the study shallow marine sediments of N Spain, mirrored the establishment of stressful marine conditions (including probably changes in salinity, ph and surface water temperatures) together with high nutrient supply towards the debut of the OAE2.
The marine productivity collapses shortly after the OAE2 instauration (i.e., in the latest Cenomanian), event that is coeval with high values of 13C, and possibly an increasing of sea-surface temperatures. During the OAE2 (lithological expressed in the study area by black shale deposition), the nannofossil preservation is very poor, feature that is probably associated with a developing of oxygen minimum zone during the Cenomanian-Turonian boundary transgression. The nannofossil Eprolithus floralis shows peaks towards the end of OAE2, nannofloral event that could be linked to surface-water temperature decrease in the late phase of OAE2.
References
Hardas, P., Mutterlose, J., 2007. Calcareous nannofossil assemblages of Oceanic Anoxic Event 2 in the equatorial Atlantic: Evidence of an eutrophication event. Marine Micropaleontology 66, 52–69.
Lamolda, M.A., Gorostidi, A., Paul, C. R. C., 1994. Quantitative estimates of calcareous nannofossil changes across the Plenus Marls (latest Cenomanian) Dover, England: implication for the generation of the Cenomanian-Turonian Boundary Event. Cretaceous Research 14, 143-164.
Lamolda, M.A., Gorostidi, A., Martinez, R., Lopez, G., Peryt, D., 1997. Fossil occurrence in the Upper Cenomanian-Lower Turonian at Ganuza section, northern Spain: an approach to Cenomanian-Turonian boundary chronostratigraphy. Cretaceous Research 18, 334-353
Paul, C.R.C., Mitchell, S., Lamolda, M., Gorostidi A., 1994. The Cenomanian-Turonian Boundary Event in northern Spain. Geological Magazine 131, 6, 801-817.
Premoli Silva, I., Erba, E., Salvini, G., Locatelli, C., Verga, D., 1999. Biotic changes in Cretaceous oceanic anoxic events of the Tethys. Journal of Foraminiferal Research 29, 4, 352-370. |
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