Oil shales from the K-Pg boundary interval of Jordan – Climate controlled archives of surface and bottom water conditions in a shelf setting

Abstract

We integrate previously published data from geochemistry, clay mineralogy, and benthic foraminifera with new findings from calcareous nannofossils and the sulfur content to reconstruct the variations of bottom and surface water conditions resulting from climate changes in the Jafr Sub-basin (Jordan). The fluctuation of the organic matter content recorded from Maastrichtian and Danian oil shales of a cored section, is seen as a response to nutrient fluxes, inducing changes in primary productivity. Bacterial workover and enrichment played a secondary role.The benthic foraminifera and calcareous nannofossils reflect oxygen depleted bottom waters and ecologically stressful surface waters. The preservation of organic matter and organic matter bound sulfur, which dominates almost throughout the entire Maastrichtian, is linked to warm-humid climatic conditions. A slight increase of the oxygen content of bottom and surface waters, which has been recorded for the latest Maastrichtian and Danian, is associated with warm-arid conditions. The biota response to these changes is documented by the extinction of most calcareous nannofossil species across the Cretaceous-Paleogene boundary, while benthic foraminifera were less affected. The short- and long-term climatic variations during the Maastrichtian-Danian interval suggest the following scenario. Riverine influx in combination with an upwelling system provided the nutrient input fueling the primary productivity of the southeastern Tethyan surface waters during the late phase of extended shelf flooding.