Micropaleontology, Paleoecology and Paleoenvironment of Well-A Samples, Niger Delta, Nigeria
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Micropaleontology, paleoecology and paleoenvironmental study was carried out on ditch cuttings from "Well A" located onshore Niger Delta, Nigeria between 2740ft - 4540ft depth intervals. The analysis was carried out to characterize the microfossil assemblages into biozones and determine the age range of Formation penetrated, determine the paleoecology affinities of the microflora and reconstruct the paleoenvironment of deposition. The study samples were described in the laboratory following the standard sample description procedures and the result generated, indicated an intercalation of sandstone, sandy shale and shale of the Agbada Formation of the Niger Delta, Nigeria. The samples were prepared into micropaleontology slides for the analysis of microfauna and microflora. The micropaleontology analysis showed that majority of the sampled depths were rare to barren in microfauna occurrences indicating a more continental depositional setting. Few foraminifera recovered included mostly, benthonics with only one occurrence of planktonic foraminifera and few miscellaneous microfauna such as shell fragments, gastropoda and pelycepoda. The microflora analysis yielded very poor palynomorphs for 2740ft-3280ft but rich in palynomorphs for the rest of the intervals under study. The palynomorphs were dominated with mostly, land derived sporomorphs such as Zonocostites ramonae, Monoporites annulatus, Pachydermites diederixi, Psilatricolporites crassus, Retibrevitricolporites obodoensis, Ctenolophonidites costatus, Echiperiporites stelae, Retitricolporites irregularis, Laevigatosporites discordatus, Verrucatosporites sp, Crassoretitriletes vanraadshooveni, Acrostichum aureum and Polypodiaceiosporites retirugatus. The palynomorphs indicated paleoecology species ranging between montane/open forest through lowland rain forest to mangrove swamp forest but predominantly mangrove swamp based on the percentage count of Zonocostites ramonae and other mangrove forms. Abundant mangrove sporomorphs suggested deposition within the lower delta plain to delta front. The preponderance of shell fragments and associating Lenticulina inornata and Quinqueloculina valgaris indicated high energy depositional setting. The presence of mostly benthic foraminifera, freshwater algae Botryococcus braunii, foraminiferal test wall lining, dinocysts indeterminate and other miscellaneous microfauna such as gastropoda, pelycepoda and shell fragments within 3520ft – 4540ft indicated shallow marine incursion (delta front). Two subzones P850 and P860 was identified based on the probable quantitative base occurrence of Nympheapollis lotus observed at 3880ft and corresponded to the broad pan-tropical Echitricolporites spinosus zone of Germeraad et al. (1968) and the P800 – P900 zones of Evamy et al. (1978). The age of the formations penetrated corresponded to Early Pliocene – Late Miocene based on the occurrences of foraminifera species such as Ammobaculites strathearnensis, Eggerella scabra, Globorotalia pseudpoima, and Quinqueloculina valgaris and corresponded to quantitative base occurrence of Nympheapollis lotus..
Publication Info:
Author: Soronnadi-Ononiwu, G.C., Ukpabi, N. and Etuk, E.E.
Volume: 57
Issue: March
Published By: Journal of Mining and Geology, 2024-03-01