Distribution of shallow-water benthics (rudists, calcareous algae, benthic foraminifers) in the Cenomanian-Turonian carbonate platform sequences of Senai, Egypt

Rudist bivalves, benthic foraminifers and calcareous algae are common in the Upper Cenomanian-Turonian Tethyan inner platform deposits of the Sinai peninsula. In this study, special emphasis is placed on the vertical distribution of these benthic organisms across the Cenomanian-Turonian transition, and on laterally varying occurrences along a N-S transect involving a sequence stratigraphic interpretation of Cenomanian and Turonian sediments. A significant disturbance of latest Cenomanian carbonate production was followed by flooding of the Upper Cenomanian inner platform during the Early Turonian and the establishment of a new carbonate platform during the Middle-Late Turonian. Diversities and frequencies of the studied fossils are distinctively different in Cenomanian and Turonian deposits. Rudists and benthic foraminifers are common in the Upper Cenomanian successions but occurrences decline drastically in the Lower Turonian and recover again in the Middle-Upper Turonian. In contrast, calcareous algae of Upper Cenomanian deposits are species-poor and flourished in the Lower and Upper Turonian. In addition to these large scale distribution trends, the occurrences of the studied benthics is closely related to regional facies belts, which prevail in individual systems tracts. Rudists occur mainly in HSTs, benthic foraminifers and calcareous algae mainly in TSTs and HSTs. The correlation of facies, systems tracts and biota distribution suggests a link between repeated reorganisation processes of the depositional system due to relative sea-level changes and the distribution of individual benthic groups.