New palynological evidence for the age of the Beda Formation, Sirte Basin, Libya

The Beda Formation represents the subsurface sequence of interbedded limestone with subordinate dolomites, which are major hydrocarbon reservoirs in the western Sirte Basin of Libya. Middle Paleocene (Montian) age has been assigned to this formation based on foraminifera, but the list of those age diagnostic foraminifera could not be found in the published literature, thus the age of this formation is questionable. Thick Paleocene-Early to Middle Eocene limestones and calcareous claystones also occur in this basin. Palynological study of 32 core samples of the Beda Formation from four different wells was carried out; but only four samples of Core # 1 (6854'-6884') in the Well # X43 yielded low diversity yet workable assemblages of palynomorphs. The pollen grains and spores indicate a Paleogene age. However, the dinoflagellate cyst assemblages provide several stratigraphically significant forms that indicate an Early-Middle Eocene age. The results of the present study suggest that either the studied samples do not belong to the Beda Formation or the age of the Beda Formation ranges from Middle Palaeocene to Early-Middle Eocene. An extensive study of large numbers of core samples from several well sections is suggested to generate new micropaleontological and palynological data that could conclusively define age of the Beda Formation.