Clay Mineral and Textural Variations in the Sediments of Chandragiri River, Estuary and Shallow Marine Realms off Kasaragod, Kerala

X-Ray diffraction and textural studies were carried out on 25 surficial sediments collected from Chandragiri River, estuary and shallow marine areas off the river located in Kasaragod district, Kerala for understanding the provenance of the clay minerals. The riverine sediments are dominated by sandy silt to silty sand, whereas the estuarine sediments consist of clayey silt to silty sand and the shallow marine sediments are dominated by clayey silt. Kaolinite and gibbsite dominate the sediments with minor amounts of illite and smectite with the complete absence of chlorite in all depositional environments, supporting the intense chemical weathering occurring in the study area. Illite is relatively higher in the shallow marine sediments compared to the estuarine and riverine sediments, suggesting the influence of morphological characteristics of clay minerals and hydrodynamic conditions in their lateral distribution. Smectite is subtly and systematically higher in shallow marine environment, which is attributed to the fine size nature of this mineral. Although various processes may redistribute clay minerals within the aquatic systems, it is possible to identify the source rocks and weathering characteristics from the detrital clay mineral studies. The major source rocks contributing towards the clay mineral distribution in the study area are the Precambrian crystalline rocks, laterites and the Tertiary sedimentary formations exposed along the coastal belt.