SEDIMENTOLOGY OF SANDBAR DEPOSITS FROM THE OVWAIN RIVER

This study examines the sediment, minerals, and chemical makeup of sandbar deposits from the Ovwian River in Udu Local Government Area, Delta State. Three samples were collected from an active mid-channel sandbar and analysed using grain-size tests, X-ray diffraction (XRD), and X-ray fluorescence (XRF).The grain-size results show that the sediments have a bimodal pattern, meaning they contain two main grain-size groups. Most of the material is fine sand (2–3 φ), followed by medium sand (1–2 φ). Very coarse and very fine particles are very low, showing that the river’s flow is strong enough to wash away mud but not strong enough to carry gravel. Sorting values (0.45–0.66 φ) indicate moderately well-sorted sands, while negative skewness suggests occasional stronger water flow that brings in slightly coarser grains. The S-curves further confirm that the sediments were deposited by steady, traction-dominated river currents.The XRD results show that quartz (51–67%) is the main mineral, with noticeable amounts of feldspar and small quantities of muscovite/illite. This mixture points to sediment coming from both basement rocks and recycled older sediments. The XRF chemical analysis shows high silica, moderate alumina, and low heavy-mineral content. Weathering indices (CIA 49–60) reveal moderate chemical weathering. Overall, the study shows that the Ovwian sandbar was formed by moderate-energy river flow, steady sediment supply, and repeated reworking of sand-sized material. These findings provide important baseline information for future environmental and geological studies on the Ovwian River.