Petroleum Source Rock Characterization of the Pindiga Formation Exposed at Pantami Stream, Gongola Sub-Basin, Northern Benue Trough, Nigeria

Abstract

The hydrocarbon potential of the Pindiga Formation exposed at the Pantami Stream section 
within the Gongola Sub-basin of the Northern Benue Trough, Nigeria, was evaluated through 
an integrated lithostratigraphic, organic geochemical, and carbonate petrographic approach 
in order to constrain source rock quality, organic matter characteristics, depositional 
environment, and thermal maturity. Detailed field-based lithostratigraphic logging revealed a 
stratigraphic succession dominated by shale, limestone, and minor gypsum interbeds, 
indicative of deposition within a predominantly marine depositional system influenced by 
relatively low-energy conditions and episodic evaporitic input. Six representative shale 
samples were subjected to Rock-Eval pyrolysis for the determination of Total Organic Carbon 
(TOC), kerogen type, generative potential, and thermal maturity parameters, while six 
limestone samples were analyzed petrographically to characterize microfacies and infer 
carbonate depositional conditions. The geochemical results show TOC values ranging from 1.2 
to 2.4 wt.%, reflecting moderate organic matter richness and suggesting a fair to good source 
rock potential. Hydrogen Index (HI) values ranging from 133 to 225 mg HC/g TOC indicate 
the predominance of mixed Type II/III kerogen, suggesting the presence of both oil-prone 
and gas-prone organic matter with mixed marine and terrestrial affinities. Tmax values 
between 421 and 430°C indicate immature to early mature thermal conditions, implying that 
the studied interval has not yet attained optimal thermal maturity for significant hydrocarbon 
generation. Carbonate petrographic analysis reveals predominantly micritic limestones 
classified as mudstone and wackestone, consistent with deposition in low-energy marine 
environments favorable for organic matter preservation. The association of fine-grained 
argillaceous facies, micritic carbonate microfacies, and moderate organic enrichment 
suggests conditions conducive to source rock development. Overall, the results demonstrate 
that the Pindiga Formation possesses fair to good hydrocarbon source rock potential; 
however, greater burial depth and enhanced thermal maturation would be required for 
optimum hydrocarbon generation and expulsion. These findings reinforce the petroleum 
prospectivity of the Pindiga Formation within the Northern Benue Trough and provide insights 
into its source rock evaluation framework.