Journal of the Geological Society of India
Vol: 67, No: 2, February 2006, pp: 189-196
Clay Mineral and Textural Variations in the Sediments of
Chandragiri River, Estuary and Shallow Marine
Realms off Kasaragod, Kerala
S. Diju1 and M. Thamban2
Department of Geology, Government College Kasaragod, Vidyanagar, Kasaragod - 671 123
2National Centre for Antarctic and Ocean Research, Department of Ocean Development, Headland
Sada,
Vasco-da-Gama - 403 804 Goa; Email: meloth@ncaor.org
1
Abstract: 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.
Keywords: Clay mineralogy, Texture, Estuarine sediment, Provenance, Chandragiri
river, Kasaragod, Kerala.