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

M. G. Anantha Padmanabha Setty ¹

Affiliations
1 National Institute of Oceanography, Panjim, Goa, IN

Abstract

Twenty-two planktonic foraminifers were identified from a few samples collected by the author aboard INS KISTNA at 9°N and 76°E, at 89 metres depth from the bottom sediment-water interface. A few of the more characteristic features of each are described. Some of the species have a geologic range from Miocene to late Pleistocene and Recent also. Globigerina hexagon a and Globoquadrina conglomerata which disappeared from the Atlantic earlier (50,000 to one million years ago) are seen to be living today in the Indian Ocean. A few species are rare and restricted forms.

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C. Madusudhana Rao ¹, M. G. Anantha Padmanabha Setty ¹

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

Abstract

A study of the distribution of iron, manganese, cobalt and nickel in sediment cores from the shelf, slope and basin regions of Bornbay-Kathiawar coast of India shows that cobalt and nickel are derived from the overlying sea water as adsorbants of manganese and iron hydroxides, clay minerals, and organic matter present in the sediment. Since the cores represent differing environments, the inter-relationship and the factors governing adsorption and fixing them in the sediment vary considerably.

Mn/Fe ratio decreases uniformly with depth in the shelf sediments excepting in one core, whereas on the slope and the basin, it indicates a gain which is due to the enclosed slum and turbidite deposits. The manganese: iron ratios for (a) the shelf cores are 1 : 72; 3 : 205; and 6: 265; (b) for the slope it is 1 : 116; and (c) the basin 6: 170. The values are highest in one core. This suggests an enrichment of manganese in the shelf region and in the basin, but great mobility in the slope and parts of the shelf resulting in depletion.

Iron-cobalt and manganese-nickel are the covariants, and hence correlatable. Significantly, the organic matter in the slope sediment is inversely proportional to the amount of manganese present in the sediment. One core shows some unusuIIy high values (56 ppm cobalt and 75 ppm nickel) as against the average values of 13 and 55, respectively, for near-shore sediments (total sediment) of North Atlantic and North Pacific.

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Rajiv Nigam ¹, M. G. Anantha Padmanabha Setty ¹, N. V. Ambre ¹

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

Abstract

Sixty-Four benthonic foraminiferids are reported from Dabhol-Vengurla innershore neritic environmentand they are listed in orderof their relative abundance. Small microenvironments or milieus createdby the dominance of Trochammina inflata and Ammobaculites agglutinens on the one handand the miliolid fauna on yhe other are noted.

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M. G. Anantha Padmanabha Setty ¹

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

Abstract

Six species of ostracodes are recorded from two transects of terraces of Deep Lake, Vestfold Hills, Antarctica. Two species (Xesteleberis sp. and Bradleya dictyon) range from Cretaceous to Recent, Poseidonamicus aff. P. major ranges from Oligocene to Recent, while Krithe tunnida ranges from Pliocene to Pleistocene to Recent. Paradoxostoma antarcticum and Loxoreticulatum fallax are reported from Antarctica and range from Pleistocene to Recent. Bradleya and Krithe were typical deep water (psychrospheric) forms during Paleocene to Oligocene as today but they were found in shallow (-45 to -37 m) depths here. Ostracodes are extremely rare as compared to the associated foraminiferal assemblage. Dissolution effect, loss of ornamentation, thinning and fragmentation of the fauna are considered to be mainly due to gradational external stress, and large scale physical environmental shifts such as high salinity, low temperature and high dissolved carbon dioxide content of the Deep Lake waters. Disparity in abundance is attributed to wind erosion, differential deposition after ablation of ice from ice sheets, physiographic variation of the region and high rate of dissolution of calcareous forms including foraminifera.

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