Lithostratigraphy of Sediments in Bashar and Environs, Northern Benue Trough, Northeastern Nigeria.

Abstract

This study investigates the siliciclastic sedimentary sequences in the Bashar area. 
located in the Northern Benue Trough, Nigeria. These sequences are critical to 
understanding the geological history of the region, particularly in terms of sediment 
provenance, depositional environments, and the diagenetic processes that have 
affected the rocks since deposition. Through a detailed analysis of lithofacies, this 
research aims to interpret the paleoenvironmental and geodynamic evolution of the 
Bashar Formation and correlate it with similar formations across the Benue Trough. 
The study utilizes fieldwork conducted across eight outcrop sections, covering the 
Bima Group, Yolde Formation, Pindiga Formation, and Gombe Formation. These 
sections were meticulously measured and described, with attention paid to 
lithological variations such as grain size, sediment composition, bedding structures, 
and the presence of sedimentary and biogenic structures. These characteristics 
were used to define distinct lithofacies assemblages and reconstruct the 
depositional environments in the study area, applying Walther’s Law of Facies 
Succession to understand the lateral and vertical facies changes over time. Key 
findings of the research include the identification of a pronounced angular 
unconformity between the Pindiga and Gombe Formations in the Bashar area, 
which is not typically observed elsewhere in the Northern Benue Trough. This 
unconformity suggests a significant tectonic event that uplifted and eroded parts of 
the basin before the deposition of the Gombe Formation. Furthermore, the study 
provides a detailed description of the Gombe Formation, which consists of two main 
lithofacies: a lower pebbly conglomerate sandstone indicative of high-energy 
braided river environments and an upper red sandstone facies deposited in more 
distal, oxygenated settings. The stratigraphic data, combined with geochemical and 
petrographic analyses offer a comprehensive picture of the sedimentary processes 
that shaped the Bashar area. The research highlights the importance of tectonics. 
sediment supply, and sea-level changes in controlling sediment deposition and basin 
evolution in the Northern Benue Trough. Moreover, the findings have broader 
implications for understanding the tectonic evolution of the West and Central 
African Rift systems and provide valuable insights into the Cretaceous 
paleogeography of northeastern Nigeria. This study contributes significantly to the 
lithostratigraphic understanding of the Northern Benue Trough, offering new 
interpretations of the depositional environments and tectonic history of the Bashar 
region. It underscores the complex interplay between rifting, subsidence, and 
sedimentation that has shaped the basin’s geological evolution since the Mesozoic 
era.