Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

Ranadhir Mukhopadhyay ¹, N. H. Khadge ¹

Affiliations
1 National Institute of Oceanography, Dona Paula, Goa 403004, IN

Abstract

The Central Indian Ocean Basin (CIOB) was subjected to tectonic reacti, vation in geological past which is unusual for a basin occurring on an apparently , single tectonic plate. ENE-WSW trending latitude parallel zone of reactivation across the central part of the basin is reported. Distinct difference in characters of seamounts, . manganese nodules and bottom sediment are found in this deformed central part as . compared to those from northern and southern parts of th'is basin. Much lower ratio of height to basal width (h/Wb) of seamounts; and presence of several guyots in this' ; central part are reported. Abundance of smaller. spheroidal, smooth textured nodules and absence of index radiolarian zone I fossil, coupled with sediment erosion of to several centimeters indicate activity of west-bound Antarctic Bottom Water (ABW) , and other turbulent water masses that later passed through the reactivated central part. The cause of this deformation is attributed to wrench.faulting as part of large scale tectonic reactivation during late Miocene.

Keywords

Indian Ocean, Tectonic Reactivation, Manganese Nodules.

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J. N. Pattan ¹, G. Pratibhan ², C. Prakesh Babu ², N. H. Khadge ¹, A. L. Paropkari ², V. N. Kodagali ¹

Affiliations
1 National Institute of Oceanography, Dona Paula-403004, Goa, IN
2 National Institute of Oceanography, Dona Paula -403004, Goa, IN

Abstract

A closely spaced 75 surface sediments drawn from "Gas Hydrate" Project taken up by National Institute of Oceanography on a regional scale from the Krishna- Godavari Basin (Latitude 15°35' to 16°20' N; Longitude 81° 40' to 82°30E) are analysed for texture, major, and some trace and rare earth elements to understand their source and provenance. Water depth in the study area varies between 300 to 2000 m and there is a WNW-ESE trending sedimentary ridge in the southwestern part of basin. Sediments are mosdy silty clay in nature. Ti - bearing minerals such as titanite and pyrophanite are evident by the strong positive correlation between Ti and Ca (r = 0.89) and Ti and Mn (r =0.67) respectively. An independent behaviour of Zr suggests occurrence of zircon mineral. The strong positive correlation among Al, Fe, Mg and K (r = 0.68 to 0.90) suggests their association with clay. The average total REE (Σ2REE 176±13 ppm) abundance is similar to that of average shale with a flat shale- normalized REE pattern suggest a terrigenous source. High concentration of Fe (6.45±0.43% ), Ti (0.82+0.07%), V (192±23 ppm), Cr (128±13 ppm) and Zr (159±19 ppm) and presence of smectite as a major clay mineral suggest that Peninsular Godavari River has sediment influx from source rocks of Eastern India mainly Deccan Trap, Precambrian and Dharwar formation. Further, it confirms that the role of Ganges-Brahmaputra River sediments to the basin appears to be small compared to the Peninsular rivers.

Keywords

Surface sediments, Geochemistry, Silty clay, Smectite, Titanite, Pyrophanite, Zircon, Bathymetry, Krishna-Godavari Basin, East Coast of India.

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