Along the east coast of India between Chennai and Pondicherry, 163 sediment
samples were collected from different sub-environments of the beach repres
enting low water mark (LWM), foreshore (FS), bt rm crest (BM), backshore (B
S), dune (DU), and beach ridge or strandline (SL), upto I tn depth, at fift
een stations, spaced at a distance of approximately 10 km interval. Out of
four size ranges (-420 to +350 mu, -210 to +177 mu, -105 to +88 mu and the
fraction consisting of the highest percentage in the sediment - first mode)
, the +88 mu size range shows rich concentration of heavies (8.26 to 96.6%)
. The heavy mineral content in the bulk sediment samples ranges from 0.55 t
o 21.95%. This concentration may be due to the winnowing by wave action and
selective sorting processes. Erosion exposes one of the stations in the be
nch ridge, up to 4 m depth from the surface and shows a higher concentratio
n of heavy minerals. This information, along with analytical results of the
stations from the surface upto one metre depth, indicating heavy mineral c
oncentration of 8%, suggests the possibility of buried pincer deposits at a
bout 2 to 4 m depth along the beach ridge. Based on this prognostication, a
random station was selected i.e. near Mahabalipuram and manual boreholes w
ere drilled. These boreholes have confirmed the existence of buried placer
deposits having concentration of 8 to 88% of heavy minerals around 1.5 to 4
m depth of beach ridge. R mode and Q mode factor analyses indicate the pos
sible environmental parameters prevailing at the time of deposition as well
as under the present conditions in the stations.