Paleoclimates and Provenance of Yolde Formation along Pantami Stream of the Gongola Sub Basin Northern Benue Trough, North East Nigeria.

Abstract

The geochemical characterization of the Yolde Formation exposed along the Pantami 
stream section was undertaken to constrain provenance, paleoweathering intensity, 
depositional conditions, and tectonic setting. A total of eight (8) representative 
mudstone samples were systematically collected and subjected to whole-rock 
geochemical analysis. Major oxide ratios and selected trace element proxies were 
evaluated using established geochemical indices. The SiO₂/Al₂O₃ ratios range from 
3.12 to 4.91, reflecting a relatively low compositional maturity and suggesting limited 
sedimentary recycling and textural immaturity of the detrital fraction. The 
Al₂O₃/TiO₂ ratios (5.25–8.69) indicate a dominant contribution from felsic to 
intermediate source rocks, consistent with derivation from continental crustal 
materials within the adjoining basement complexes. Paleoclimatic conditions inferred 
from Sr/Cu ratios (3.45–9.70) suggest deposition under predominantly arid climatic 
regimes, which likely influenced both sediment supply and diagenetic evolution. The 
Chemical Index of Weathering (CIW) values range from 84.80% to 93.36% (average 
= 89.01%), indicating intense chemical weathering within the source area, possibly 
under prolonged subaerial exposure and effective leaching of mobile cations. Redox
sensitive trace element ratios further constrain depositional conditions; Ni/Co values 
ranging from 0.24 to 1.44 (average = 0.57) are indicative of oxic depositional 
environments, suggesting well-oxygenated bottom waters during sediment 
accumulation. Tectonic discrimination based on SiO₂ versus K₂O/Na₂O relationships 
places the Yolde Formation within a continental rift to passive margin transitional 
setting, consistent with the evolution of the Gongola Basin as part of the failed rift 
(aulacogen) system associated with the opening of the South Atlantic. Collectively, 
these geochemical signatures provide robust constraints on the provenance, 
paleoclimate, weathering intensity, and depositional framework of the Yolde 
Formation in the study area.