Paleosalinity and hydrothermal characteristics of the Upper Cretaceous Duwi black shales, Aswan Governorate, Egypt

Abstract

: The Upper Cretaceous Duwi black shales of Nile Valley district, Aswan Governorate, Egypt, were geochemically examined to determine their paleosalinity and hydrothermal characteristics present at the time of their deposition. Elemental ratios such as strontium/barium (Sr/Ba) and TOC/S were applied for paleosalinity reconstruction. The Duwi black shales show Sr/Ba >0.5 and TOC/S ˂5. The values of the elemental ratio show that the Duwi black shales were deposited in a marine environment. For hydrothermal activities ratio, Sc/Cr was used and Binary diagrams TOC vs P were constructed to discriminate between normal water, mixed and hydrothermal influence. The Sc/Cr ratio was ˂0.120 indicating that the black shales in the Nile Valley district were deposited in a hydrothermal water environment. The binary discriminant diagram of TOC vs P shows that all the shales were influenced by hydrothermal processes during the time of their deposition.