Geochemical characterisation of mangrove sediments in Tiko (SW, Cameroon, West Africa): Implication for provenance, paleoweathering and sediment maturity

Abstract

Geochemistry was performed on clastic core sediments from the Tiko Mangroves estuary, South western region of Cameroon, to categorise the rock source composition, tectonic setting, past weathering intensity of the source area in relation to past climate and sediment maturity in relation to sedimentary cycle. Plots of La/Co, La/Sc, Cr/Th, discriminant function (DF1&2), TiO2vs Al2O3 and TiO2 vs Zr point to an acid (felsic) and mixed (intermediate) rock source composition for the Tiko sediments. The acid composition portrayed by the sediments is also confirmed by their LREE (Light rare earth elements) abundance, and a negative Europium anomaly on chondrite normalisation, while the intermediate (mix) composition reflects the multiple sources of the sediments (Douala Basin and basaltic debris from Mount Cameroon). Binary plots Discriminant function (A-P) M, and Discriminant function (A-P) MT signpost active tectonic domain for the studied sediments, that resulted from the tectonothermal of the Pan African orogenic history and eruptive activity of the mount Cameroon. The weathering indexes denoted as CIX (chemical index of weathering) and PIX (plagioclase index of weathering) for the Tiko sediments advocate an intense source area weathering in a humid hot climate. The PIX advocate a high-level plagioclase lixiviation. The low values of ICV (index compositional variation) less than 1 (<1) couple with correlation plots Zr/Sc vs Th/Sc, and Zr vs (La/Yb)N confirms that Tiko mangrove sediments are matured recycled sediments with compositional variations. This is the first comprehensive provenance study of mangrove ecosystem sediments in Cameroon.