Paleoclimatic cycles, sea level history and sequence stratigraphic elements in eocene–oligocene sediments of BIMOL-1 well northern Niger Delta Basin, Nigeria

Abstract

Lithofacies succession and palynomorph data trends in BIMOL-1 well in the north-western Niger Delta Basin have been investigated in order to unravel paleoclimatic influence on paleo-sealevel change and facies evolution. Eight lithologic cycles composed of sand and shale were identified. Miospore speciation revealed forty two miospore form species and ten dinoflagellate cyst species. Miospore and dinocyst trends revealed six climate driven sea level cycles that influenced sedimentation and facies distribution and characteristics. Miospore age determination of the succession revealed L-Eocene to L-Oligocene age range. Nine wet and eight dry climate driven transgressive and regressive events were identified, corresponding to sea level rise and to sea level fall correspondingly. Dry climate occasioned continental progradation that generated thick sand intervals, while wet climate triggered sea level rise, generating thinner sand bodies as transgressive sand reservoirs. Seven high stands (HSTs), eight transgressive (TSTs) and eight lowstand (LSTs) systems tracts, distributed within nine sequences were identified. Candidate MFSs, the 50.0 Ma, 48.9 Ma, 46.1 Ma, 43.2 Ma, 41.0 Ma, 34.0 Ma MFSs were identified. Candidate SBs identified include the 50.7 Ma, 48.4 Ma, 47.2 Ma, 44.4 Ma, 42.7 Ma, 40.1 Ma and 32.4 Ma SBs. Early Rupelian sequence boundaries were identified. Erosion/non-deposition of the Priabonian and parts of the Bartonian stage were revealed that inferred erosion/non-deposition of about 7 Ma of sediments in the well area. A synthesis of results of the evaluated proxies revealed that Paleoclimate-driven sea level and paleovegetation trends acted as key facies generators in the well area.

Keywords: Paleoclimateic cycles, climate driven sea level, Niger Delta, climatic index