Coupled geochemical and foraminiferal response to environmental changes during the deposition of Upper Cretaceous oil shale in the Negev, Israel

Peter Illner, Sarit Ashckenazi-Polivoda, Zsolt Berner, Sigal Abramovich, Ahuva Almogi-Labin, Shimon Feinstein

Research output: Contribution to conferencePaper

Abstract

The accumulation of a 40 m thick oil shale sequence during the latest Campanian marks a major change in the dynamics of the Late Cretaceous southern Tethys upwelling system. Based on the vertical distribution of foraminiferal taxa, Ashckenazi-Polivoda et al. [1] established a high resolution
paleoenvironmental scheme, defining five planktic (P-Type) and five benthic foraminifera (B-Type) assemblages which thrived under distinct bottom-water aeration and surface water productivity conditions. Principal component analysis of major and trace elements concentrations in the studied sequence allows distinguishing three factors. The first reflects the interplay between biogeniccarbonate (Ca, Sr) and terrigenous input (Al, Si, K, Ti, V, Fe, Ga, Nb, Ba, Pb, Th). The second mirrors the degree of bottom water oxygenation (Corg, S, Ni, Cu, Zn, As, Cd, Mo, U vs. Mn), while the third factor stands for conditions that promoted phosphorite deposition (P, Y, La, U). The comparison of these
chemostratigraphic features with the distribution of the foraminiferal assemblage types as defined in [1] points to a strong interdependence between these geochemical and micropaleontological environmental indicators. The
distribution of the planktic assemblages P-Types 1 and 4, and the benthic assemblage B-Type 4 parallels the variations in the degree of bottom water oxygenation and detrital input. P-Type 1 and 2 (high Heterohelix) assemblages coincide with a gradual decrease in biogenic carbonate production and a relative weak anoxic response to the increase in terrigenous input. In contrast, assemblages P-Type 4 (dominance of Globigerinelloides) and B-Type 4 (triserial buliminids and Gavelinella), limited to the base of the oil shale, are characterized by strong anoxia and high carbonate production, as reflected by scores of factors 1 and 2.
Original languageEnglish
StatePublished - 1 Jan 2011
EventGoldschmidt Conference 2011 -
Duration: 30 Jan 2011 → …

Conference

ConferenceGoldschmidt Conference 2011
Period30/01/11 → …

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