Dinoflagellates from the Miocene Rudeis and Kareem formations borehole GS-78-1, Gulf of Suez, Egypt

Abstract

The Miocene Rudeis and the Kareem formations encountered in the Neogene part of the GS-78-1 borehole, Gulf of Suez produced diverse assemblages of dinoflagellate cysts, spores and pollen. The Early Miocene (Burdigalian) age assigned to the Rudeis Formation and the Early-?Middle Miocene (Langhian–Serravallian) age postulated for the Kareem formation is based on the presence of dinoflagellate cysts. These offer a good basis for biostratigraphic correlation of the Miocene deposits in the Gulf of Suez with those in the Nile Delta and Sinai in Egypt, and also with those present in key sections from the Mediterranean, the Canadian offshore sequences, Northwest Europe and from the North Atlantic. The terrestrial palynoflora (spores and pollen) affords no really precise, independent testimony as to the age of the samples, apart from being generally indicative of a Neogene age, in accord with the established gross age of the sediments, derived mainly from planktonic forams, calcareous nannoplankton and dinoflagellate cysts. The Rudeis Formation was deposited in a relatively deep water environment, based on the abundance fluctuations in miospores and dinoflagellates. However, the miospores recovered from the Rudeis Formation give an equivocal signal with respect to depositional environment. Such observed incursions of terrestrial elements in the Rudeis Formation could indicate that they might have been carried about within the basin of deposition by the waters of the Mediterranean Sea, or that they were displaced into a deep water setting. The overlying Kareem Formation was identified as an outer continental shelf deposit to upper bathyal (distal) environment because it contains a higher percentage of marine dinoflagellate cysts in most investigated samples, except in its uppermost part which shows the lowest percentage of marine forms. These include Spiniferites ramosus, S. pseudofurcatus, Operculodinium centrocarpum, Polysphaeridium zoharyi, Systematophora placacantha and Lingulodinium machaerophorum. The consistent presence of P. zoharyi in the Kareem Formation indicates that the Gulf of Suez was at times in the tropical to subtropical belt during the Early-?Middle Miocene age.