Variations and Quartz Grain Microtextures in Sediments from the Central Part of the Gulf of Guinea: Implications for Sedimentary Processes and Depositional Environment

Abstract

In order to identify the sedimentary processes, depositional environment, and provenance, the study used sieving and SEM-EDS to analyze the particle size and quartz grain microtextures from sediments in the central part of the Gulf of Guinea. Samples were collected from three locations (Yoyo, Mbiako, Mouanko) for grain size analysis and particle size parameters such as mean, sorting, skewness, and kurtosis were determined. In general, the sediments are dominated by medium-grained sands (81.14%). The descriptive statistics and bivariate relationship plots of different particle size parameters show that the sediments are medium to fine, moderately well classified, fine-to-very fine skewed towards fine with platykurtic. Most of the sands come from a river-type environment, as well as beaches, and transported by saltation. The transport mode of the fine sands is dominated by suspension transport. Rolling is the dominant mode of transport for coarse sands. Twenty-five features were known and clustered according to their types of origin. Among them, eighteen features characterize the mechanical origin, four belong to the chemical origin, and three represents mechanical/chemical origin. Quartz microtextures show that the mechanical, mechanical/chemical, and chemical are mostly associated with fluvial, littoral, and aeolian processes. The quartz grains in the sediments from the central part of the Gulf of Guinea are resulting mostly from crystalline source rocks. Furthermore, shapes (angular, subangular, sub-rounded) indicate that these sediments were transported by a medium to high-energy environment, short transport or quick deposition. Moreover, occurrence of sub-rounded grains militated for far-source materials.