Dinoflagellate Cyst Biozonation Of Upper Cretaceous Succession Of Mbeji-1 Well Central Chad Basin North East Nigeria

Abstract - The dinoflagellate cysts from the Upper Cretaceous succession penetrated by Mbeji-1 well in the Chad Basin Nigeria were investigated. The investigation yielded biostratigraphically significant dinoflagellate cyst species recovered from interval 1600m - 3720m of the well. Based on the stratigraphic distribution of these bioevents five informal dinoflagellate cyst assemblage zones from the Cenomanian to Maastrichtian are proposed. The zones in stratigraphically ascending order are as follows Subtilisphaera inaffecta Zone I Odontochitina operculata Zone II Coronifera oceanic Zone III Exochosphaeridium muelleri Zone IV and Hystrichodinium pulchrum Zone V. The ages of these zones based on stratigraphic positions and series of first occurrences of key species are Cenomanian-Turonian Zone I Coniacian-Santonian Zone II Santonian Zones III-IV and Campanian-Maastrichtian Zone V.