Palynostratigraphy and Age Determination of Bima Formation, Yola Basin, Northern Benue Trough, North East Nigeria

Abstract

Bima Sandstone which is known to be from Early Cretaceous is the oldest formation that has been identified in the Northern Benue  Trough. Bima Formation whose age has been studied by several authors is known to be Aptian – Albian and older but no specific age has  been pegged for the older sediments which has created a need for more work to be conducted on it. This study used cuttings from two  boreholes, to enable a thorough investigation of the palynological content of Bima Formation and its age. A palynostrtigraphic studies  was conducted on sediments of Bima Formation penetrated by of Tula 1 and Tula 2 boreholes. A total number of 64 spores, pollens and  dinoflagelates species were recovered from 150 borehole cutting samples. These species comprise of 33 spores, 25 pollen, and 6 dinoflagellates. In terms of age determination species like the Afropollis zonatus and Afropollis operculatus are significant marker  palynomorphs of Aptian age while Afropollis jardinus, and pollens like the Elaterosporites verrucatus and Elaterosporites klaszii indicates  an age not older than Albian. Concavissimisporites punctatus, Elaterosporites Klaszii, together with Oligosphaeridium complex support  an Aptian/Albian age. The presence of Appendicisporites spp., Cibotiumspora fuxingensis, Cicatricosisporites sinuosus,  Gnetaceapollenites barghornii, and Clavatipollenites hughesii which are guide stratigraphic markers of Barremian sediments confirm the  older Bima Formation sediments to be of Barremian age. Presence of Ephedripites is related to Barremian age, the abundance of  Ephedripites aegyptiaca and Gnetaceapollenites barghornii, is an indication that the sediments is not older than Barremian.