Upper Cretaceous (Coniacian -Campanian) siliciclastic/carbonate ramp depositional sequences and relative sea-level changes in Sinai, Egypt: Implications from facies analysis

摘要

Through the analysis of biostratigraphy, facies types and distribution, lithofacies associations, and bounding surfaces, we derived high-resolution sequence stratigraphy of the mixed siliciclastic-carbonate rocks for four sections in the Coniacian-Campanian succession in Sinai (Egypt). These stratigraphic sections provide a framework for studying the sedimentary-facies evolution, the paleogeography, and the role of eustatic and tectonic processes in Egypt and surrounding countries. Twenty-six foraminiferal species and four foraminiferal zones (the Dicarinella concavata Interval Zone in the upper Coniacian, Dicarinella asymetrica Total Zone in the Santonian, Globotruncanita elevata Partial Range Zone in the lower-middle Campanian, and Globotruncanita ventricosa Partial Range Zone in the middle Campanian) are noted. Twenty-three lithofacies and microfacies types into six facies associations ranging from progradational shoreface to outer ramp are detected and categorized. These facies associations exhibit lateral variation and deepening toward the north from siliciclastic-carbonate (Matulla Formation) to dominant carbonate (Themed Formation). Three sequences separated by four sequence boundaries have been determined in the field and/or from strong vertical facies changes associated with short time gaps representing the Turonian-Coniacian; the lower-middle and upper Coniacian; the upper Coniacian-Santonian; and the Santonian-Campanian stage boundaries. Comparisons of the examined sequence boundaries in Egypt and in some parts of Europe, within the Arabian Plate, and in global charts suggest that eustatic and tectonic effects were simultaneous.