Chronostratigraphy of the Upper Cretaceous high productivity sequence of the southern Tethys, Israel
Meilijson, Aaron × Ashckenazi-Polivoda, Sarit Ron-Yankovich, Libby Illner, Peter Alsenz, Heiko Speijer, Robert Almogi-Labin, Ahuva Feinstein, Shimon Berner, Zsolt Puettmann, Wilhelm Abramovich, Sigal #
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
CRETACEOUS RESEARCH vol:50 pages:187-213
The Levantine high productivity sequence is a product of an extensive upwelling system that operated in the Late Cretaceous along the SE Tethyan margin. This system resulted in the deposition of a unique sequence of carbonate, chert, porcellanite, phosphorite and organic-rich (oil shale) sediments in a series of basins located proximally and marginally to the upwelling center. This study presents a detailed and updated chronostratigraphic framework for the high productivity sequence in Israel based on eight sections covering a NeS cross section of w90 km. The Shefela Basin (central Israel) represents the thickest and the most complete penetrated stratigraphic interval of the oil shale deposits in Israel. The newly drilled Aderet borehole in the Shefela Basin provided a continuous core record coupled with high
quality geophysical well logs and was used in this study as a ‘type-section’ for the detailed chronostratigraphic
scheme of the high productivity sequence. A total of 23 datum levels were recognized using planktic and benthic foraminiferal biostratigraphy, lithostratigraphy and gamma ray well log markers. The varying lithostratigraphic units (containing chert, phosphate, porcellanite and organic-rich
carbonates) of the more proximal basins of southern Israel (Negev) were individually correlated to specific horizons within the monotonous organic-rich carbonates of the distal setting of the Shefela Basin.
The first occurrence of the Late Cretaceous organic-rich carbonates in Israel is documented in the Negev during the late Coniacian, within the upper Dicarinella concavata Zone, and corresponds chronologically to the upper part of the lower Menuha Formation. The regional unconformity around the Santonian/Campanian boundary was found to be less substantial at the distal localities in comparison to
the proximal ones. The distinct appearance of the ‘Mishash Tongue’ chert in the Shefela was correlated to the massive Chert Member (Mishash Formation) in the Negev, and assigned to the middle Campanian.
Deposition of the overlying phosphate series spans from the lower Contusotruncana plummerae to the base of the Pseudoguembelina palpebra Zones (78.3e71.7 Ma) and co-occurs in both proximal and deeper distal areas, although in a much lesser magnitude in the latter. The top of the phosphatic unit is marked by a regional unconformity. The oil shale deposits in southern Israel coincide with the 100 m richest TOC interval (average of 15.2 wt.% TOC) in the Shefela. The diminishing phase of organic-rich deposition occurred in a diachronous step-wise manner across Israel, from the top of the P. palpebra Zone to the upper part of the Abathomphalus mayaroensis Zone in southern and central Israel, respectively. This indicates that the full duration of the high productivity sequence in Israel spans approximately 19 myr.