பூமி அறிவியல் & காலநிலை மாற்றம் இதழ்

சுருக்கம்

Neogene Deep Water Agglutinated Foraminiferal Biostratigraphy and Biozonation in Niger Delta, Nigeria

Ajayi EO, Agboneni OE

This study entails the biostratigraphy of benthic agglutinating foraminifera of four wells in the deep water of the Niger Delta. A total of 453 ditch cuttings were analysed for wells A, B, C and D. Eighty-five and 164 ditch cuttings from the intervals of 4900–9920 ft. and 4530–14600 ft. of wells A and well B respectively, while 92 and 112 cuttings from 5760–11400 ft. and 6000–12750 ft. were analysed in wells C and D respectively. These samples were processed and analysed at 60 feet intervals. . The analysed sections of the wells are composed of shale, mudstones and sand deposited in the upper to lower bathyal environments. The agglutinating foraminifera recovered were fairly well preserved. Total foraminifera percentages recovered from wells A, B, C and D wells are 31%, 34%, 24% and 27% respectively. Marker species were identified and used to erect biozones. The following six agglutinated foraminiferal zones beginning from the oldest have been proposed, Eggerella scrabra Taxon Range Zone, and Ammobaculites strathearnensis–Eggerella scabra, Haplophragmoides narivaensis - Eggerella scabra, Cyclammina cancellata–Ammobaculites strathearnensis, Cyclammina complanata–Glomospira gordiales, Cyclammina cf. minima–Ammobaculites strathearnensis Interval Range Zones. The agglutinated foraminifera assemblages were calibrated to the geologic timeframe by means of planktic foraminifera and calcareous nannofossils. The studied wells penetrated a sedimentary succession of Late Miocene to Early Pliocene age. Taxonomic notes on some of the observed species have also been provided.