Post Tsunami Heavy Mineral Distribution Between Cuddalore to Kanyakumari Along the Tamil Nadu Coast, India – A Review

Abstract

Placer deposits are formed as a result of the selective concentration of valuable minerals from the disintegration and redeposit ion of the rock fragments. Beach sands contain the most economically important minerals accumulations; wave action deposits sand on the beach and the heavy minerals are concentrated when backwash carries some of the lighter minerals such as quartz back into the sea. Onshore winds which preferentially blow lighter grains inland can lead to higher concentrations of heavy minerals at the front of coastal dunes. Old 'fossil' shorelines known as strandlines can now be found some distance inland. Minerals with following inherent characteristics can be accumulated as placers such as high specific gravity and, chemical strength to resist the denudating action of transporting agent. Placer deposits can be broadly classified on the basis of mode of origin and transportation into eluvial, deluvial, proluvial, alluvial (sub divided into bar, channel fill, valley delta and bench or terrace placers) lateral (subdivided into lacustrine, beach, marine beach, and offshore placers) glacial (subdivided into marine and fluvioglacial) and Aeolian placers (Smirnov, 1976). Rajamanickam (1993) has classified (l) marine placers including raised beaches (2) offshore placers including (i) ongoing and (ii) palaeo/fossil placers of both buried and exposed types. Many works are concentrated on beach placers (Angusamy and Rajamanikcam, 2000, Cherien, 2003, Mohan, 2001) however, only limited work has been carried out for tsunami placer mineral studies. Worldwide tsunami impacts of the last century have been documented by many researchers (Heck, 1947; Iida et al., 1967; Nakata et al, 1993; Lander and Whiteside, 1997; NGDC, 2001 and Shi et al 1995, Maramai et.al., 2005; McMurtry et. al., 2004; Scheffers and Kelletat, 2003; Tappin et.al., 2001; Nanayama et. al., 2000; Clague et.al., 2000; Dominey-Howes et. al., 2000; Papadopoulos and Chalkis 1984; Monge and Mendoza, 1993; Morner, 1999). (Angusamy & Rajamanickam 2000) have studied