Palynomorphs Distribution, Biostratigraphy and Paleoecology Study of the Superficial Sediments in Parts of Gombe Formation, Upper Benue Trough, Nigeria

摘要

Paleoecological conditions of part of Gombe formation of Upper Benue Trough were studied using outcrop samples from 22 sites of 1.5 m deep each. The samples were crushed, standard maceration method employed for analysis and slides prepared. The slides were examined for identification and counting using transmitted light microscope with times one hundred oil immersion objective lenses. The result showed a fairly rich assemblage of palynomorph which includes age diagnostic palynomorphs: Cingulatisporites ornatus, Proteacidites sigalli, Constructipollenites inflectus, Echitriporites trianguliformis, Longapertites microfoveilatus, Monocolpites sp. and Tricolpites sp. which effectively assigned the upper Maastritchtian age to the sequence. Also the abundance of woody and vegetal materials which are land derived in the shales, siltstones and kaolinite rich claystone at the upper part of the sequence studied suggest the prevalence of fresh water conditions. The presence of Ephedripites in some sections of the sequence studied reflects occasional dry conditions. The high abundance of Acrostichum aureum in sample BA-8 signifies flooding of the region in Maastrichtian times by the sea characterized by shallow water depth and restricted ecological circulation which also occurs in mangrove forest and other wetlands.