Calcareous Nannofossil Biostratigraphic Analysis of Well ‘K-2’, Deep Offshore Niger Delta, Nigeria

Abstract

A study on the calcareous nannofossil biostratigraphy has been carried out on sequences within the interval 1640m-1980m of well ‘K-2’ located in the deep offshore of Niger Delta, Nigeria. Lithologic description of the samples was done using a stereo-binocular microscope. Thirty-four slides of samples were prepared and studied for their calcareous nannofossil contents using Olympus Light Microscope in both plane-polarized and cross-polarized light. The lithostratigraphic descriptions on the samples showed the abundance of shale and mudstone/siltstone with minor amount of thin intercalated units of sand bed. Seventeen calcareous nannofossil species were identified and used to predict the biostratigraphic deductions such as zonation, dating and a tentative sequence stratigraphic framework. With the aid of a standard zonation schemes, two major nannofossil zones (NN 19 and NN 18) were identified. These zones belongs to Pleistocene and Pliocene ages respectively. Two major zones of Gephyrocapsa carribeanica and Gephyroca psaparallela were identified for the studied well on the basis of the index taxa and fossil assemblage recorded.  The insufficient amount of nannofossils in the lower part of the well precluded a definite zonation and made the zone to be indeterminable. One Condensed Section believed to be associated with 2.0Ma Maximum Flooding Surfaces was recognized.