Palynology and petrographical composition of Agbani sandstone and its environs

This study examined semi-unconsolidated surface outcrop samples from three different localities within the Agwu Formations of the Lower Benue Trough (SE Nigeria). This paper focuses on the palynology, petrographic composition and depositional conditions of the three areas by using Quartz, Feldspar and Lithics (QFL system) petrography, including quartz ratios, and palynology. The composition of the Agwu samples is similar to that of the Agbani samples. Lithologic description showed that some sections of the outcrops were ferruginized and calcareous. The sandstone samples from both locations are characterised by a high content of quartz group, ranging from 46 to 95%. The prevailing mineral from this group is calcite (31%–65%), which is indicative of a low degree of the litification of organic matter. Relatively low contents of feldspar are very minimal (not exceeding 9%) and rock fragments (not exceeding 8%) were also determined and palynomorphs were poor. The content of minerals is inferred from microscopic studies and is variable but generally high, varying from 35 to 75%, similar to that of other formations within the study area; it consists mostly of quartz, calcite and clay minerals. This input of mineral matter is probably related to periodic inundations of mangrove swamps which reflect the influence of oxidizing conditions during deposition. The age prediction of the palynomorphs was indeterminate.