Palynology and stratigraphy of the Upper Miocene Chad Formation, Bornu Basin, northeastern Nigeria

One main palynological zone, i.e., the Echitricolporites spinosus assemblage zone, has been established. The base of the studied section at 385 m is characterized by the last up-hole occurrence of Grimsdalea magnaclavata suggestive of Eocene boundary while the overlying sediments are characterized by Late Miocene marker species such as E. spinosus, Elaeis guineensis, Anthocerus sp., Nymphaea lotus, and Retistephanocolpites gracilis. The Chad Formation is dated as Late Miocene age unconformably overlying the Eocene Kerri-Kerri Formation which indicated that the Chad Formation was probably deposited during an alternation of lacustrine and continental settings, due to climatic change.