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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.

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Estimation of the bottom (Curie) depths and SHF values on blocks (A, B, C, …, Y) of magnetic anomalies in the lower and part of the middle Benue trough and Anambra basin have been presented. A Map of the result shows a shallow Curie depth of about 11 km around the area of Abakaliki with the deepest Curie depth of about 27 km obtained around Utukpa region. The overriding bottom (Curie) depth of 18 km is calculated around Iku mbur, Arufu and Igumale regions. Heat flow has also been calculated from the Curie depth results. The SHF vary from 54 mWm–2 around Utukpa to the highest value of 132 mWm–2 around Abakaliki. The obtained high SHF value could be of sufficiently good prospects for the exploration of geothermal energy resources in the region.

A multi proxy investigation was carried out on three outcrop sections (NL4, NL8, NL10) in the Upper Cretaceous Numanha Formation in the Yola Arm of the Upper Benue Trough, northeastern Nigeria. The Numanha Formation is a predominantly shale sequence that preserves the Turonian-Coniacian depositional history of a rift basin influenced by both the Tethyan and Atlantic oceans. Thirty-eight samples from two sections (NL4 and NL10) were analyzed for palynofacies characterization of the sedimentary organic matter contents, while the total organic carbon (TOC) and carbon-to-nitrogen (C/N) ratios were analyzed in 44 samples from all three sections. Palynofacies data confirm an overall marginal marine (estuarine) depositional setting for the Numanha Formation which was strongly impacted by terrestrial and freshwater sources of sedimentary organic matter. This interpretation is based on the following observations: 1) near constant presence of marine dinoflagellate cysts and/or benthic planispiral microforaminiferal inner test linings; 2) abundant vascular plants fragments such as opaque, structured, and degraded phytoclasts with fluxes of cuticles at certain intervals; and 3) near constant presence of the freshwater alga Pediastrum which was also recorded in high proportions at certain intervals. TOC contents in the majority of the analyzed samples were generally low (<1%), indicating poor organic matter preservation potential probably due to high energy and well oxygenated conditions. C/N ratios were mostly below 20 in the samples from all sections, and confirm the inferred marginal marine depositional setting. There were, however, two exceptionally high C/N anomalies in all three sections. The anomalies were especially pronounced in the NL4 section, and were also associated with elevated TOC contents. It appears that these anomalies represent periods of increased terrestrial input, which were also associated with selective diagenetic consumption of nitrogen by microbial degradation.