Biozonation and Sequences Stratigraphy of Maastrichtian to Danian Sedimentary Succession in Alo-1 Well, Anambra Basin
1Lucas, F. A., 2Osezele, E. I. & 3Ebahili, E. O.
1,3Department of Geology University of Benin, Benin City, Nigeria
2Geology and Geophysics Department, Skangix Development Limited, Lagos, Nigeria
Email: drfalucas@gmail.com, preshyose143@gmail.com, ebahili789@yahoo.com
ABSTRACT
A detailed palynological study of One hundred and five (105) ditch cutting samples recovered from depths ranging from 540ft to 8,600ft were recovered from Maastrichtian to Danian sedimentary succession penetrated by Alo-1 well in the Anambra Basin, Nigeria was carried out. It yielded biostratigraphically significant dinoflagellate cyst species. A total of 81 species of miospores and 19 dinocysts were identified, evaluated and appraised for their biostratigraphic utilities. Maastrichtian to Danian stage is assigned for the succession penetrated. The Cretaceous –Tertiary (K-T) boundary is delineated by both the FAD of a dinocyst species, Damassadinium californicum and LAD of a pollen species, Constructipollenites ineffectus at intervals 3,600ft and 4,360ft respectively. Palynomorph abundance pattern and the age of the succession penetrated were used to delineate stratal surfaces: two maximum flooding surfaces (MFS) and one sequence boundary (SB) were defined in the Danian, three maximum flooding surfaces (MFS) and two sequence boundaries (SB) were defined in the Maastrichtian. Based on the age established for the succession penetrated, the formations likely penetrated by the well were established to be the Imo (Danian) from 540ft-3600ft and Nsukka (3600ft-4570ft)-Ajali (4570ft-5170ft) and the Mamu (5170ft-8600ft) these have been dated Maastrichtian to Danian. The two maximum flooding surfaces were mainly delineated and defined on the basis of palynological signals while the sequence was identified on the basis of the high resolution lithofacies model generated for the well sedimentary succession.
Keywords: Maastrichtian; Danian; Dinocysts; Biozonation; Sequence stratigraphy.
