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

G. Gaitan Vaz ¹

Affiliations
1 East Coast Operations 11, Marine Wing, Geological Survey of India, 41, Kirlampudi Layout, Visakhapatnam - 530 017, IN

Abstract

Green and brownish green grains associated with surficial sediments of outer continental shelf and subsurface sediments of upper slope off Chennai have been investigated for their distribution. The green and brownish grains account for 40% of the sediments in the outer continental shelf while in the upper slope the green grains account for 20-90% of the sediments. X-ray diffractograrns reveal that the grains from outer shelf are mainly composed of Phyllite V clay mineral of the verdine facies and a mixture of detrital clays. The grains from the upper slope constitute glauconitic slnectite and glauconitic mica of the glaucony facies. The ferric oxide and potassium oxide contents of the grains confirm their verdine and glaucony facies respectively. Their distribution pattern signifies the palaeobathymetric and palaeoenvironmental conditions of the area. Glaucony facies in upper continental slope apparently belong to the period of Last Glacial Maximum (LGM) and verdine facies in outer continental shelf to subsequent transgression.

Keywords

Marine Geology, Verdine, Glaucony, Continental Margin, Chennai, Tamil Nadu.

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G. Gaitan Vaz ¹, G. P. Mohapatra ¹, M. Hariprasad ¹

Affiliations
1 East Coast Operation II, Marine Wing, Geological Survey of India, 41, Kirlampudi Layout, Visakhapatnam - 530 017, IN

Abstract

Red sediments occur as three shore linear patches between Bavanapadi and Ichchapuram in north Andhra Pradesh coast. The unstructured red sediment lying over an antecedent topography is divisible into lower unit with calcretes and upper unit devoid of calcretes. The field observations, grain size parameters, heavy mineral assemblage and SEM studies of quartz grains signify an aeolian source, possibly formed by sand transport from the exposed continental shelf during the Quaternary regressive cycles. Formation of calcrete and red pigments are considered as post depositional phenomena. SEM studies of ilmenite, XRD and chemical studies of finer fractions reveal the in situ derivation of red haematite and goethite pigments from the alteration of ilmenite and precipitated interstitially to give rise to red colour.

Keywords

Palaeoenvironment, Red Sediments, Quaternary, Aeolian, Ilmenite Alteration, Andhra Pradesh.

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G. Gaitan Vaz ¹, V. Subba Rao ², V. Ravikumar ³

Affiliations
1 Operations East Coast-11, Marine Wing, Geological Survey of India, NH-5, Marripalem, Visakhapatnam-530 018, IN
2 Operations East Coast-II, Marine Wing, Geological Survey of India, NH-5, Marripalem, Visakhapatnam-530 018, IN
3 0perations Andhra Pradesh, Southern Region, Geological Survey of India, Hyderabad-500 068, IN

Abstract

Five thermal springs under artesian conditions are recorded around Manamelkudi in western areas of Palk Bay. These thermal springs are in association with E-W trending faults. The field data and coastal geomorphic signatures of the area suggest that the E-W trending faults are deep seated, extending to offshore area off Manamelkudi and neotectonically active location of seismographs in the region is recommended in view of the above.

Keywords

Thermal Springs, Active Fault, Seismicity, Palk Bay.

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G. Gaitan Vaz ¹, P. Vijaykumar ¹

Affiliations
1 East Coast Operations II, Marine Wing, Geological Survey of India, 41, Kirlampudi Layout, Visakhapatnam - 530 017, IN

Abstract

Seabed survey off the southern part of Cauvery basin revealed the exposure of well indurated ferruginous fossiliferous limestone in the upper continental slope ESE off Nagapattinam. The presence of benthic foraminifera] fossil viz. Miogypsina sp. assigns Upper Oligocene - Lower Miocene age to the ferruginous limestone. The limestone exposure in the upper continental slope suggests the northeasterly offshore extension of the sub-basin viz., Ramnad - Palk Strait Depression.

Keywords

Ferruginous limestone, Continental slope, Cauvery basin, Miogypsina sp., Upper Oligocene-Lower Miocene.

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G. Gaitan Vaz ¹

Affiliations
1 Geological Survey of India, East Coast II, Marine Wing, Visakhapatnam - 530 017, IN

Abstract

No Abstract.

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