Sediment geochemistry of coastal environments, southern Kerala, India: implication for provenance

Late Quaternary sediments representing the floodplain, estuary and offshore environments of southern Kerala were investigated to infer provenance. The grain size reveals the dominance of sand to silty clay, clay to clayey silt and clayey silt in the floodplain, estuary and offshore sediments, respectively. The chemical index of alteration (CIA) values and A-CN-K plot attributes to high, moderate and low weathering in floodplain, estuary and offshore regions, respectively. The SiO 2 /Al 2 O 3 values lesser than Post-Archean Australian Shale indicate low to moderate maturity for the estuarine and offshore sediments. The geochemical immaturity indicates its derivation from low to moderately weathered source rocks. The major and trace elemental ratios and discriminant function diagrams attribute that the sediments were derived from intermediate to felsic source rocks. The enrichment of Cr and Ni concentration in the sediments compared to the upper continental crust, related to the contribution of orthopyroxenes, weathered from charnockite and garnets from the granulite terrain, respectively

Provenance and tectonic setting of Miocene siliciclastic sediments, Sibuti formation, northwestern Borneo

Provenance and tectonic setting of sandstone and mudstone units of the Miocene Sibuti Formation from northwest Borneo have been studied based on the mineralogy, major and trace element geochemistry data. The X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) data revealed that the sandstones and mudstones were abundant in quartz, pyrite, clay, and heavy minerals such as zircon, rutile, and some detrital cassiterite. Geochemically, the sandstones and mudstones are classified into quartz arenite, litharenite, sublitharenite, arkose, and wacke. Quartz arenites are enriched with SiO2, Zr, and Th and depleted in Al2O3, CaO, and other elements compared to other sandstone types, indicating high maturity and intensive weathering. Chemical index of alteration (CIA: 77–90), plagioclase index of alteration (PIA: 86–100), and A-CN-K diagram suggest intense weathering in the source area. Elemental ratios such as La/Sc, Th/Sc, Cr/Th, La/Co, and Th/Co are similar to sediments derived from the felsic rocks. Also, the provenance discrimination diagrams suggest recycled continental nature of these clastic sediments which are mostly derived from metasedimentary source (Rajang Formation). Discriminant-function diagram for the tectonic discrimination of siliciclastic sediments revealed that the sediments of Sibuti Formation were derived from a collision zone, which is consistent with the geology of the study area