TITLE:
Granulometric and Environmental Characteristics of Surface Sediment Deposits in the Ouaka River (Central African Republic)
AUTHORS:
André Jules Ouambeti-Wickon, Gabriel Ngueutchoua, Doria Grace Takenne, Armand Sylvain Ludovic Wouatong, Prince Emilien Danguene
KEYWORDS:
Particle Size Analysis, River Deposition, Hydrodynamic Energy, Saltation Transport, Linear Discriminant Functions
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.13 No.12,
December
22,
2025
ABSTRACT: The sediments of the Ouaka River were analyzed on the basis of samples taken from the banks during the dry season. These sediments consist of gravel, sand and silt-clay. These sediments are being studied in a context where the sand from the Ouaka River is going to be used for major construction work on road infrastructure and administrative buildings. In this context, the granulometric analysis of these sediments revealed the dominance of medium sands, silt-clays and, secondarily, coarse sands. The grading curves for these sediments show a sigmoidal “S” shape, indicating that they were deposited in a river and in a depositional environment with relatively high hydrodynamic energy. These sediments, transported and deposited by various hydrodynamic energies, are linked to the massive arrival of materials from secondary watercourses tributary to the Ouaka River. Most of the gravel moves by rolling. Most sand moves by saltation. Silt-clays move essentially by suspension. The Passega diagram describes transport of these gravels by rolling over the bottom. The combined Friedman, Moiola and Weiser diagrams show sediments of fluvial origin and those influenced by sand dunes from the Chad Basin. Analysis of the linear discriminant functions reveals a turbulent fluvial environment with shallow marine beach inputs in turbulent waters. This marine influence is linked to the presence of limestone in the catchment, which is generally formed in a marine palaeoenvironmental context. As part of this study, the distribution of heavy minerals was highlighted in order to determine the origin of sediments from the Ouaka River. These sediments contain mainly tourmaline, rutile, sillimanites, opaque minerals and other heavy minerals. The majority of the sediments are mineralogically immature to sub-mature since the Zircon-Tourmaline-Rutile maturity index is less than 75%.