Potent Tools in Reconstruction of Palaeoclimatic Condition of Sedimentary Facies in Zuma Coal Mine, Ankpa, Anambra Basin, North Central Nigeria

Abstract

 The formation of sedimentary rocks, especially those associated with coal seams, depends on several factors, including climatic conditions. This is a strong factor that is responsible for the sea level changes and is indirectly responsible for weathering, sediment transportation, deposition and vegetation. Therefore, reconstruction of the palaeoclimatic conditions of Zuma sedimentary facies was carried out by integrating eustatic change in sea levels through the application of sequence stratigraphy with change in vegetation patterns through the application of various palynomorphs such as pollen, spores, dinoflagellate, algae and fungal spores. The lithofacies samples studied indicate intercalation of coal seams bounded by claystone/shale facies at intervals which tend to vary with vegetation pattern and sea level changes. The basal part of the sequence consists of marginal marine claystone deposits characterized by a quantitative abundance of palynomorphs. This suggests the presence of a TST system tract belonging to a wet climatic condition due to an increase in sea level. The middle part of the sequence consists of coal deposits with a substantial amount of palynomorph abundance and diversity, marking the onset of the rising sea level (TST), of which the coastline migrated landward as a result of a shift in climatic conditions from dry climate to wet climatic period. Above the middle part of the sequence indicates a climatic change from a wet to a dry climatic condition, which is characterized by low palynomorph abundance and paucity in palynomorph diversity, having a low-stand systems tract of a fall in sea level. As a result of the dry climatic conditions in this interval, there is low organic matter content at this interval compared to the basal part of the sequence, which has abundant organic matter content and potential for hydrocarbon generation in the area.