Paleoenvironmental changes of the Cenomanian-Early Turonian shallow marine carbonate platform succession in west central Sinai, Egypt

The Cenomanian to Early Turonian succession in the study area is represented by the Raha Formation (Abu Had Member and Mellaha
Sand Member) and Abu Qada Formation. During the deposition of the Abu Had Member, the northward increase of the carbonate facies
refers to the northward deepening of the shallow marine platform. Also, the increase of calcareous facies upwards indicates a continuous
rising of the sea level. The occasional occurrence of laminated black shale, infaunal large benthic foraminifera with sporadic occurrence
of high-stressed planktonic foraminifera and high proportions of cytherellids mark intertidal restricted environment with dysoxic
conditions. The successive last appearance of most large benthic foraminifera upwards refers to successive bioevents. The sudden
disappearance of fossils within the overlying Mellaha Sand Member is attributed to shallow intertidal conditions (shallow inner ramp)
of a short term regressive phase with terrigenous influx. During the deposition of Abu Qada Formation, the increase of carbonate facies
represents a new transgressive phase following the regressive phase of clastic Mellaha Sand Member. The flourishing of various soritid
survivors associated with other large agglutinated forms and dasyclad algae in the base of Abu Qada Formation suggest inner to middle
ramp. Within the upper part of Abu Qada Formation, the dominance of opportunistic heterohelicids, surface dwellers whiteinellids,
calcisperulids and remnants of larval stage of bivalves reflect rising of the sea level in middle and outer ramp with increased primary
productivity and a long-term expansion of the oxygen minimum zone near the Cenomanian–Turonian boundary that coincides with the
Oceanic Anoxic Event 2.