Taphonomy and paleoecology of Cenomanian oysters from the Musabaa Salama area, southwestern Sinai, Egypt

摘要

This work is a taphonomic and paleoecologic study of Cenomanian oysters from the Musabaa Salama area, southwestern Sinai, Egypt. Disarticulation, fragmentation, encrustation and bioerosion are considered as the most predominant taphonomic features recorded in the studied oyster assemblages. Their distribution and frequency are greatly varied within the shells of the same species, as well as between shells of different species through the recorded oyster zones. Bioerosion structures include Tiers D, E, F, G and H. The multivariate statistical analyses document some characteristic ichnocoenoses. They include a sponge-dominated community (Entobia ichnocoenosis), a bivalve-dominated community (Gastrochaenolites ichnocoenosis), a serpulid-polychaete-dominated community (Maeandropolydora, Trypanites and/or Caulostrepsis ichnocoenosis), and an acrothoracican cirriped-dominated community (Rogerella ichnocoenosis). With rare exceptions, E. cretacea, G. torpedo and M. decipiens are common to abundant ichnospecies (> 43%). E. ovula, E. retiformis and R. pattei are frequent to common ichnospecies (> 5%). Other ichnospecies, including C. cretacea, G. orbicularis, T. solitarius, E. geometrica and C. taeniola are rare to frequent (< 3%). Careful investigation of the host shells and the preserved encrusters and/or bioerosion sculptures provided data concerning the substrate characteristics, time of encrustation and bioerosion, rate of sedimentation, nutrients availability, and the general bathymetry and the rate of transgression.