V. Santhosh^a*, Akash Padmalal^b, S. Vishnu Mohan^c, P.K. Abdul Nafih^a and A.R. Malavika^a

^aDepartment of PG Studies and Research in Geology, MES Ponnani College, Ponnani-679586, Keralam, India

^bDepartment of Geology and Environmental Science, Christ College, Irinjalakkuda, Thrissur-680125, Keralam, India

^cDepartment of Geology, Sree Narayana College, Varkala, Thiruvananthapuram-695145, Keralam, India

(*Corresponding Author, E-mail: santhoshviswapal@gmail.com)

Abstract

The coastal lowlands of Kerala in southwest India are endowed with deposits of fluvial and marine and aeolian mineral resources. Kerala’s beach placers are a major and strategic mineral source in the area. Apart from beach placers, the coastal area in and around Alappuzha district has vast amounts of silica sand that occur between the Vembanad Lake and the seashore, spanning for about 35 km from Cherthala to Arookutti. Although many studies have been carried out on Kerala’s beach placers, studies on silica-sand deposits of Alappuzha-Cherthala belt are very limited. Therefore, the present study addresses the textural and mineralogical characteristics of the Alappuzha-Cherthala belt. Fine sand comprises 11.2% to 57.3% in the surface sediments, while in the subsurface samples fine sand varies from 25.66% to 66.5%. Both the surface and subsurface sands are moderately to well sorted. These sands are in general coarsely skewed and leptokurtic. The mineralogical analysis reveals that opaques, sillimanite, and zircon dominate in the heavy mineral assemblage. The CM pattern revealed that the sands were generally transported by rolling and suspension. High sillimanite concentrations in the samples suggest a sialic metamorphic origin for silica sands. Long beach currents carried sillimanite and quartzose sands from the coastal extents of the Trivandrum Block in the south (south of Achankovil lineament) towards the Alappuzha-Cherthala coast, which is later modified into the silica sand deposits during the aridity event in the beginning of Late Holocene.

Keywords: Silica Sands, Alappuzha-Cherthala belt, Heavy minerals, Granulometric analysis, CM pattern