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| Titel |
Integrated bio-chemostratigraphy of Late Cretaceous organic-rich marine sediments in Israel |
| VerfasserIn |
Nitzan Mizrahi, Yehudit Harlavan, Sigal Abramovich, Sarit Ashckenazi-Polivoda |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250145960
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| Publikation (Nr.) |
 EGU/EGU2017-9945.pdf |
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| Zusammenfassung |
| The Late Cretaceous was a time of great climatic and paleocanographic changes that had
major impact on the global marine ecosystems. The timing of these events must be accurately
determined based on a reliable chronostratigraphic framework that can be readily applied in
various environmental settings. The Late Cretaceous planktic foraminiferal biostratigraphic
zonation is mainly based on tropical-subtropical species that are typically found in normal
pelagic settings. However, during this time, unique conditions of high water column
productivity and oxygen deficiency prevailed throughout the Levant region, including Israel,
causing a partial to total exclusion of some of these species. Consequently, establishing age
framework based on biostratigraphic correlation of the Levant region is a challenging
task, emphasizing the need to apply additional method to advance the regional
chronostratigraphy. Among these, is chemostratigraphy based on the 87Sr/86Sr ratio in
of the carbonate tests of foraminifera, which is now widely used for stratigraphic
correlation.
The main objective of the present research was to improve the chronostratigraphic
resolution for the Upper Cretaceous organic-rich sequence in Israel. This was accomplished
by integrating detailed correlation of planktic and benthic foraminiferal bioevents, with
87Sr/86Sr ratio, correlated to the global 87Sr/86Sr ratio curve. This integration provides a new
and much improved chronostratigraphic framework of the Late Cretaceous strata of Israel and
the entire Levant region. It allows to integrate sections with poorly preserved or lack of the
common biomarkers, define for the biozone. In general this should yield the best age control
for economically valuable stratigraphic units (e.g., oil shale) deposited during this
time.
The biozonation of the studied sections, RE-2 and RE-6 from the Negev basins (southern
Israel), spans from the Late Santonian Dicarinella asymetrica Zone to the middle
Maastrichtian Abathomphalus mayaroensis Zone and from the middle Coniacian Dicarinella
concavata Zone to the early Maastrichtian Pseudoguembelina palpebra Zone, respectively.
The zonation subdivision, and the regional correlation to Aderet borehole from the Shefela
Basin, Central Israel, is based on 23 secondary and main planktic biomarkers and based on
the LOs of seven benthic species namely Anomalinoides praeacutus, Laevidentalina
gracilis, Loxostomum decurrens, Angulogavelinella abudurbensis, Siphogenerinoides
parva, Neoflabellina rugosa and Gaudryina rugosa and the acme event of Elhasaella
alanwoodi. Sr isotopes curves from the RE-2 and Aderet sections show a remarkable
correlation to the global Sr curve and with good agreement with the biostratigraphy
datum.
We took great measures to ensure that the analyzed 87Sr/86Sr ratio on ca. 200 tests per
sample will represent the tests themselves and not impurities. Overall, the results are with
agreement with the global 87Sr/86Sr ratio curve.
Ultimately, the results of this study assess the accuracy and applicability of the secondary
planktic and benthic foraminiferal datum to determine important age intervals and for
determining numerical ages based on the Sr isotope records. Our new chronostratigraphic
framework of the high productivity sequence in Israel is not only essential for regional
correlation of these economically important sediments but also valuable in a global context. |
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