A Cretaceous dinoflagellate cyst palynozonation of northern Egypt

Abstract

ABSTRACTThe multiplicity of dinoflagellate cyst biozones in Cretaceous rocks limits their correlation applications, and the variations in the scientific bases of such zonations complicates age determinations and limits the validity of reliable inter-basinal correlations. The present work provides a useful summary of the dinoflagellate cyst occurrence data in Egypt and a proposed working Egyptian biozonation scheme for the area. The most diagnostic dinoflagellate cyst bioevents, in a definite time interval which occurs widely in most of the studied Egyptian, North African and Tethyan sections, are selected to be marker taxa for the erected zones. The eastern Canadian and northern European data consistently show much higher range tops for the dinoflagellate cysts at those high latitudes. The comparison and correlation of the contemporaneous dinoflagellate cyst range tops from Egypt and geographically neighbouring North African areas are vital for selecting widely distributed marker taxa and testing their validity and applicability to intercontinental correlations in the Tethyan Realm. Based on 29 wells located across Northern Egypt, this work provides a potentially useful scheme that unifies the different previously established dinoflagellate cyst palynozonation frameworks for Cretaceous rocks. The index palyno-events represented by the last occurrence datums (LODs) of the marker dinoflagellate cyst taxa are carefully picked from palynostratigraphies established earlier and methodically, consistently used to create a new regional palynostratigraphical scheme for all of the northern Egyptian territory. Ten dinoflagellate cyst interval zones were identified and described; these are, in descending stratigraphic order from youngest to oldest, Dinogymnium acuminatum (Maastrichtian–Campanian), Odontochitina operculata (Santonian–Coniacian), Cyclonephelium vannophorum (Turonian), Dinopterygium cladoides (late–middle Cenomanian), Coronifera oceanica (middle–early Cenomanian), Oligosphaeridium complex (late–middle Albian), Subtilisphaera perlucida (early Albian), Cribroperidinium orthoceras or C. edwardsii (Aptian–late Barremian), Muderongia simplex or Pesudoceratium anaphrissum (Barremian–late Hauterivian) and Systematophora silybum (Hauterivian–Berriasian).