Palynological Studies of Sediments from North Chioma-3 Well, Niger Delta and its Palaeoenvironmental Interpretations

Abstract

Problem statement: The Niger Delta Nigeria stands among the world's best-studies delta complexes but its superficial deposits are among the poorest known publicity. In spite of continuous oil prospecting production in the area, there is still a paucity of published information and data on the palynology of the Niger Delta. This study aimed at reconstructing the palaeoenvironments of the Niger Delta from a detailed palynological framework. Approach: Twenty ditch cutting samples from 1271-2131 m from North Chioma-3 well, Niger Delta, Nigeria, were studied and analyzed for their lithological and palynological contents. This essentially comprised of the lithological and textural characteristics survey and laboratory processing using the method of pollen analysis. Results: Seven lithological units were delineated for the well sediments made up sandy shale, shaly sand and shale typical of the Benin and Agbada Formations of the Niger Delta, Nigeria. The sediments of the investigated intervals are fairly rich in microflora which documents diverse, fairly well-preserved palynomorphs. A total of 46 pollen and spore species were recovered and identified from the well. The dominant pollen grains are those of Rhizophora spp., Poaceae and spores of pteridophytes and fungi. Palaeoecological interpretation of the interval suggests a mangrove swamp environment for the sediments and the high percentage occurrence of Rhizophora spp. indicates the abundance of mangrove swamp vegetation in the environment. Four pollen zones (I-IV) were recognized from the pollen diagram which reflects vegetational and climatic fluctuations during the period the studied sediments were deposited. Conclusion: There was a prevailence of savanna vegetation during the period covered by zone I, typified by the consistent occurrence of Poaceae pollen indicating cool and dry climate. An establishment of both wet and warm climate as well as mangrove forest vegetation was indicated for the periods covered by zones II, III and IV, with the largest extension of mangrove vegetation occurring in zone III.