Pebble Morphometric studies of the Cretaceous Lokoja Formation exposed around Karara- Banda area, North Central Nigeria

Abstract

Field study, Pebble morphometry and X-ray diffraction analyses of the Cretaceous
Lokoja Formation have been carried out in the Karara-Banda region of Bida Basin.
These analyses aimed to understand the transportation distance, mineralogical
composition, sediment maturity and depositional environment of the formation.
The Basement complex is unconformably overlain by the Lokoja Formation
according to field observations. It is made up of sandstones that may be found in
the Lokoja area between Karara-Banda. Conglomerates are found near the base of
the lithology, followed by sequences of coarse-grained to fine-grained sandstones,
siltstones, and claystones. One hundred pebbly and pebbly sandstone samples were
collected from four outcrops in the study area. Pebble Morphometric analysis
indicate clear evidence of river transport sediment for the studies Lokoja Formation
based on mean sphericity of > 0.66 as well as MPSI and OPI values. The results show
that the sediments in the basin are deposited after short travel in an oxidizing
environment under fluvial system while the pebbles are products of neighbouring
basement rocks of western and northern Nigeria