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| Titel |
Cretaceous/Tertiary boundary in the Eastern Carpathians: evidence from stable isotopes, mineralogy and calcareous nannoplancton |
| VerfasserIn |
A.-V. Bojar, Mihaela C. Melinte-Dobrinescu, H.-P. Bojar |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250021029
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| Zusammenfassung |
| This study presents the first integrated analyses of stable isotopes, mineralogical, and calcareous nannofossil data from a continuous Upper Campanian to Maastrichtian red bed sequence, including the K/T boundary interval, situated in the bend area of the Romanian Carpathians. The semi-quantitative calcareous nannofossil investigations have focused on six taxonomic groups, such as Watznaueria barnesae, Micula spp., Boreal nannofossils, Tethyan nannofossils, Braarudosphaera bigelowii, and the calcareous dinoflagellate genus Thoracosphaera. The nannofosil investigations show that the sequence spans the Upper Campanian and the whole Maastrichtian stage, including the K/T boundary. Calcite is present in all samples and varies from values up to 70 % down to 2 %. Its concentration varies in opposite direction with the concentration of layer silicates (smectite, chlorite, illite). Quartz and feldspars are plotted together and their content varies between 20 and 40 % and show no systematic fluctuations or long term trends. The delta 13C and d18O values are constant in the Upper Campanian and lower Maastrichtian red marls of the Gura Beliei Formation. In the upper Maastrichtian, lithological, mineralogical and nannofossil changes, together with several negative delta 13C and delta 18O excursions suggest instability of the ecosystems related to climatic changes and/or late Cretaceous tectonic phase. At the Cretaceous/Tertiary boundary, both d13C and d18O values show a negative excursion. Above the Cretaceous nannofossil mass extinction, successive blooms of the dinoflagellate genus Thoracosphaera and of the nannofossil species Braarudosphaera bigelowii were identified. Each of these blooms is marked by successive increases in productivity and positive delta 13C excursions. |
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