Palynostratigraphy and paleoenvironmental analysis of late Miocene- early Pliocene sediments from ML-1 well, Offshore Eastern Niger Delta, Nigeria

Detailed palynological and palynofacies studies of ditch cuttings samples from ML-1 well, Niger Delta, were carried out to construct a stratigraphic scheme. The palynofloral assemblage is quantitatively dominated by mangrove and brackish to freshwater swamp taxa with moderate abundance of Monoporites annulatus. Botryococcus braunii was common with few dinoflagellate cysts. The recorded palynomorph assemblages enabled the delineation of one major palynological zone, the Verrucatosporites usmensis pantropical zone. This zone can be correlated to zone P800 and revealed four subzones (P850, P860, P870 and P880). The age of the strata penetrated by ML-1 thus ranges from late Miocene to early Pliocene. Seven floral zones were recognised, which are associated with the dry and wet paleoclimatic phases. Palynological assemblages include relative abundances of terrestrial palynomorphs, small- to medium- sized palynomaceral types I and II (opaque phytoclast) with low occurrences of structureless organic matter, small- to medium- sized of palynomaceral types III and IV, and rare occurrence of marine palynomorphs. This indicates coastal- deltaic depositional environments in dysoxic- anoxic conditions. The palynofacies assemblage of ML-1 well are interpreted as type III kerogen, and the sediments are gas prone at greater depth. The integration of palynological and palynofacies analyses reflect two depositional sequences and comprise a sequence boundary (SB), a maximum flooding surface (mfs), and three parasequences. The findings of this study may aid in the refinement of sequence stratigraphic frameworks and in the reconstruction of the depositional environments of Niger Delta region.