Palynofacies and sea level changes in the Upper Cretaceous of the Yola Basin, Northern Benue Trough, Northeastern Nigeria

Abstract

Upper Cretaceous sediments (Numanha and Lamja Formations) in the Yola basin of Northern Benue Trough have been investigated in order to characterize the particulate organic matter (POM) in the samples. The aim is to understand the rapid facies changes in both vertical and lateral direction of the formations and the relative abundance of the different organic components within the sections. The investigation involved 62 samples from four outcrop sections. The analysis involved series of laboratory procedure ranging from sample preparation, chemical treatment with HCl and HF, sieving, slide cover and completion then the counting of 300 particles per sample. The samples yielded sufficient organic residues for detailed palynofacies analysis. The organic constituents observed in the studied samples have been classified into phytoclast, palynomorp and amorphous organic matter groups. The phytoclast group predominates in almost all the sections followed by the palynomorp group with little amount of amorphous organic matter (AOM). The palynofacies parameters used for the study are the continental/ marine and opaque/translucent ratios which led to the construction of the sea-level variation pattern for the formations using Tilia 2.0.2 program.