GEOCHEMICAL AND SEDIMENTOLOGICAL INVESTIGATION OF UNUSUAL HEAVY MINERAL LAMINATION IN TIDAL FLAT OF CHANDIPUR, ODISHA, INDIA: PROBABLE INFLUENCE OF ANTHROPOLOGICAL ACTIVITY

Concentration of heavy minerals in form of heavy mineral lamination are frequently observed in several depositional environments. In tidal flat area, heavy mineral lamination generally forms under prolonged aeolian reworking of sediments and hence directly correlate to degree of aeolian reworking with additional information about provenance, if they retain pristine composition.

A tidal flat (~4km wide) is seen in Chandipur, Odisha along East Coast of India. River Budhabalanga, source of sediments and heavy minerals in this area, is flowing roughly NW-SE to converge with the Bay of Bengal, developing prominent estuary and mouth bars. Adjacent to the estuary, the tidal flat developed. Behind the tidal flat, a small region developed as beach environment which is subaerially exposed. Trenches have been cut in foreshore and backshore region of the beach on 4 locations across the entire tidal flat. Near the estuarine end of tidal flat, an estuarine bar developed on NE end of the study area with prominent heavy mineral lamina on surface as well as in vertical sections. In the SW end, there are large scale aeolian dunes with heavy minerals concentrated along aeolian super-surfaces as well as in foreshore and backshore region. Heavy mineral laminas are also noticed in trench sections in mouth bars near estuary. In contrast to the two extreme ends of tidal flat, there are no heavy mineral laminas in the trenches in the area in between where, behind the beach area, plantations of large trees have been made artificially to form a forest.

EPMA result indicates the heavy minerals to be detrital Ilmenite. They are similar in their composition all across the tidal flat and they are probably derived from Singhbhum Craton by the river. River borne sediments are redistributed by tidal currents across the tidal flat and beach and later exposed to prolonged aeolian action to form heavy rich lamina.

Since artificial forest blocks wind action and hinders sediment reworking, heavy rich lamina couldn’t form in the area in between NE and SW end of tidal flat and heavies remained dispersed throughout the sediments. This is justified by absence of aeolian structures in the beach area in between. This is a evidence of anthropological activity influencing sedimentary processes.

Keywords: Chandipur – Detrital Ilmenite – Provenance – Heavy mineral– Tidal flat