--> Biostratigraphy and Palaeoenvironmental Reconstruction of Limestones Exposed at Sagamu Quarry, Eastern Dahomey Basin, by Seun O. Oredein and Adewale Akinmosin; #90037 (2005)

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Biostratigraphy and Palaeoenvironmental Reconstruction of Limestones Exposed at Sagamu Quarry, Eastern Dahomey Basin

Seun O. Oredein and Adewale Akinmosin
Olabisi Onabanjo University, Ago-Iwoye, Nigeria

Twenty samples were collected from sediments exposed at the Lagos end of the Shagamu Quarry and were subjected to petrographic and micropalaeontological studies. This is to reconstruct the depositional environment, possible age and to correlate the sediments with other basins from some parts of the world. Petrographic analysis revealed three limestone facies namely: shelly biomicrite, intrasparite and bio-intrasparite from bottom to the top respectively. Eight foraminiferal species consisting of five benthonics (which includes; Quinqueloculina seminulum, Textularia sp., Quinqueloculina microcostata, Bolivina sp., and Lenticulina midwayensis) and three planktonics (Morozovella Aequa, Morozovella aragonensis, and Pseudohastigerina wilcoensis) and six ostracoda species were observed and described. The planktonics form indicate an age range of Palaeocene/Eocene boundary to lower Eocene. The benthonics and the Ostracoda indicate a lagoonal to inner neritic environment with little influence from middle neritic. This falls within the region of Oceanic upwelling with salinity range of 10-35%. The study area has been correlated with more established faunal zones of the world.