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Biostratigraphy And Paleoenvironment Of The Coniacian Awgu Formation In Nzam-1 Well, Anambra Basin, Southeastern Nigeria.

2013; IJSTR; Volume: 2; Issue: 3 Linguagem: Inglês

2277-8616

Ola-Buraimo A. Olatunji,

Geological Studies and Exploration

Ditch cutting samples from an exploratory Nzam-1 well located in the northwestern part of Anambra Basin were subjected to lithological description and palynomorph enrichment and analysis through digestion with Hydrofluoric acid (HF) and floatation with Zinc Bromide (Zn2Br4). The study was intended to determine the relative geologic age and paleoenvironment of deposition of Awgu Formation through the application of palynologic tool. The lithostratigraphy of Awgu Shale is mainly shaley in nature and diagenized at different degrees within various stratigraphic levels. Palynological study revealed that the sequence is dominated by angiosperm pollen such as Monocolpites sp, Tricolpites sp and Retimonocolpites sp. Other diagnostic forms that characterize the formation include Zlivisporites blanensis, Peromonolites perireticulatus and Odontochitina sp. Thus, the Awgu Shale is dated Coniacian age. However, new forms of dinoflagellates appeared in the sediments that are suggestive of transitional environment of deposition. INTRODUCTIONstratigraphic study of the Anambra Basin continues to attract attention because it is imperative to understand the stratigraphic complexity of the basin. Though, one would have expected that it is only the eastern part of the basin (Abakaliki Syncline) that should contain Pre-Santanian sediments according to literature (Nwachukwu, 1972, Nwajide, 1990). However, the northwestern part of it in which the Nzam-1 well analyzed belongs; it is found to also contain Pre-Santonian facies. This observation been noted in the work of Ola-Buraimo and Akaegbobi, (2012a); Ola- Buraimo, (2013) for the same area of the basin. Thus, Awgu Shale which has been dated by other means is here investigated using palynological tool for the first time in order to determine relative geological age, compare palynomorph assemblages contained in it to other older formations based on the assemblage of forms that are distinctively different from the adjacent formations and finally to determine the paleoenvironment of deposition of sediments deposited within the formation.