Characterization of the Beach Rock, Underlying Placer Mineral-Sand Deposit, Visakhapatnam Coast, Andhra Pradesh

The so-called beach rock along the Visakhapatnam coast is exposed where the overlying placer deposit (sand dunes and red sediments) is eroded or removed. The morphology of samples reveals a well preserved density stratification, layering, grain size variation and alternate layering of light and heavy mineral fractions Textural characteristics confirm their derivation from beach environment. The mineral composition is similar to the present day beach sands and includes quartz, sillimanite, ilmenite and other opaques, monazite and zircon, with conspicuous absence of garnet X-ray diffraction analysis of the cementing matenal revealed the presence of siderite and himonite Study of polished beach rock specimens under the reflected light revealed exsolution features in ilmenite grains, similar to present day ilmenite Carbonate cementing matenal is replaced by secondary iron oxide. The associated flat pebbles are of quartzite and khondalite. The in situ occurrence of the beach rock along this part of the coast forms the physical evidence supportmg the coastal submergence during the Holocene transgression. The formation of beach rock is resultant of a combined marine and groundwater activity m the intertidal zone.