A.V. Udayanapillai^1*, V. Perumal¹, J. S. Armstrong-Altrin² and M. Satyanarayanan³

¹Department of Geology, V.O.Chidambaram College, Tuticorin – 628008, India

²Unidad de Process Oceanicos y Costeros, Instituto de Ciencias del Mar y Limnologia,

Universidad Nacional Autonoma de Mexico, Circuito Exterior s/n, 04510 Mexico D.F., Mexico

³CSIR-National Geophysical and Research Institute, Uppal Road, Hyderabad- 500007, India

*E-mail: avupillai@gmail.com; geo6perumal@gmail.com

Abstract

Calcrete has been formed as a widespread deposits having sub aerial exposures with thick profile in the regolith part of Sathankulam region (Latitude 08º 23′: 08º 30′ N and Longitude 77º 51′: 77º 59′ E), Tuticorin district of Tamilnadu, India. The spatial collection of calcrete samples from various outcrops reveals that the calcrete occurs as gravel, nodular, hardpan, oolitic, massive or laminated and chalky forms. The micromorphological study reveals that carbonate precipitation was in the form of micritic and sparitic calcite, which show colloform, peloidal, lensoidal, veining and void lining/rimming with unaltered clasts of quartz, feldspar, hornblende, biotite and hypersthene, sesquioxide impregnation with calcified algal mats and calcified fungal hypae preservation. The analytical results of major element of calcrete indicates that CaO, MgO, SiO2, Al2O3, Fe2O3 andtotal carbonate content (TCO3) have elevated concentration of >1% than the other oxides such as MnO, TiO2, Na2O, K2O and P2O5. The GIS based thematic iso-elemental contour maps gives the spatial analysis of major element distribution in the study area. The depositional environment of the study area is worked out from the geochemical characteristics of calcrete deposit.

Keywords: Micromorphology, Regolith, Sathankulam, Clasts, Spatial analysis, GIS