Paleoceanographic reconstruction of the late Cretaceous oil shale of the Negev, Israel: Integration of geochemical, and stable isotope records of the organic matter

Aya Schneider-Mor, Heiko Alsenz, Sarit Ashckenazi-Polivoda, Peter Illner, Sigal Abramovich, Shimon Feinstein, Ahuva Almogi-Labin, Zsolt Berner, Wilhelm Püttmann

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33 Scopus citations

Abstract

The Levantine high productivity system was an extensive coastal upwelling that operated in the Late Cretaceous along the SE Tethyan margin. This study focuses on the top Phosphate Member of the Mishash Formation and the Oil Shale Member (OSM) of the Ghareb Formation (latest Campanian-early Maastrichtian), which represent the last phase of this high productivity system in the Negev, Israel. Bulk organic matter (TOC), δ 13C org, δ 15N org, C/N and pristane/phytane (Pr/Ph) ratios, were studied for reconstruction of seafloor and water column depositional environments. Our records indicate a gradual decrease with time in surface water productivity in the OSM and a marked weakening at the overlying Marl Member. High C/N ratio along with relatively low δ 15N org (4‰ to 6‰) and δ 13C org (-29‰ to -28‰) probably reflect significant diagenetic preferential loss of nitrogen-rich organic compounds enriched with 15N and 13C isotopes (e.g. proteins). This along with the low Pr/Ph values (0.11-0.7), indicate oxygen depleted bottom water (anoxia-dysoxia) during the deposition of the top Phosphate Member and the OSM. The moderate gradual upward increase in δ 15N org, and in Pr/Ph values and the decrease of TOC and C/N values from the top Phosphate Member through the OSM indicate transition from anoxic (Phosphate-lower OSM) to dysoxic (middle-upper OSM) conditions. This environmental trend is consistent with co-occurring foraminiferal assemblages in the studied succession and implies that the benthic species in the Negev sequence were adapted to persistent minimum oxygen conditions by performing complete denitrification as recently found in many modern benthic foraminifera.

Original languageEnglish
Pages (from-to)46-57
Number of pages12
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume319-320
DOIs
StatePublished - 15 Feb 2012
Externally publishedYes

Bibliographical note

Funding Information:
We wish to express our gratitude to S. Volin and Amir Eyal, from Rotem Amfert Negev Company for their cooperation, to M. Kitin from the Geological Survey of Israel for his assistance in the laboratory procedures, and to Dr. Thomas Gentzis from Core Laboratories, Houston for the organic petrology analysis. We thank Alon Amrani for his helpful comments on this manuscript. We greatly thank reviewers Mark R. Leckie and Philip A. Meyers for their significant contribution towards improvement of this paper. The research was supported by GIF — The German-Israeli Foundation for Scientific Research and Development — grant no. 956-38.8/2007 , the Israeli Ministry of National Infrastructure grant no. 27-17-005 and the Robin and Harold Vinegar contribution.

Keywords

  • C/N ratio
  • Late Cretaceous upwelling system
  • Negev Oil Shale Israel
  • Pr/Ph ratios
  • TOC
  • TON
  • δ C
  • δ N

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