Palynostratigraphy and palaeoclimate of the Valanginian–Cenomanian subsurface succession in Hamza-1X well, Matruh Basin, Egypt

Abstract

Diverse palynomorph assemblages of spores, pollen grains and dinoflagellate cysts have been yielded from the palynological analyses of 115 ditch cutting samples covering the Valanginian– Cenomanian succession encountered in Hamza-1X well, Matruh Basin, north Egypt. The complex sit- uations in the north Western Desert requires more revisited palynozones for better understanding of the subsurface successions therein. Consequently, the first downhole palyno-events will be very helpful in solving some issues concerning the age determination and correlation. Seventy palynomorph species (47 spores and pollen grains; 23 dinoflagellate cyst species) were identified from all the productive samples which used to divide the studied succession into numerous sporomorph and dinoflagellate biozones based on the last occurrence datum for the recovered marker taxa. Four sporomorph inter- val biozones and six dinoflagellate cyst interval biozones were differentiated from the same studied stratigraphic succession. The four sporomorph biozones are presented, in ascending order as follows: Aequitriradites spinulosus and Impardecispora apiverrucata Interval Zone (late Valanginian– early Barremian), Pilosisporites trichopapillosus I. Z. (late Barremian), Murospora florida I. Z. (early Aptian–late Aptian), and Elaterosporites klaszii I. Z. (early Albian– early Cenomanian). The seven dinoflagellate cysts biozones are Muderongia simplex I. Z. (late Valanginian–early Barremian), Pseudoceratium anaphrissum I. Z. (late Barremian– early Aptian), Cribroperidinium edwardsii I. Z. (early Aptian), Subtilisphaera perlucida I. Z. (late Aptian), Oligosphaerdium complex I. Z. (early– late Albian), Dinopterygium cladoides and Coronifera oceanica Assemblage Zone (early Cenomanian). From the palaeoclimatic point of view, the studied interval could be differentiated into two climatic intervals; the lower arid interval that comprises the Alam El Bueib Formation and dominated by the arid xerophyte elements like Sphaeripollenites and Classopollis. The upper humid interval represents the Alamein, Dahab, Kharita and Bahariya formations that is dominated by the humid hygrophyte elements, such as Murospora, Crybeolsporites, Elaterosporites, Afropollis and Deltoidospora.