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

Sanjeev S. Thakur ¹, R. T. Arasu ¹, V . S. R. Subhramanyam ¹, A. K. Srivastava ¹, A .V. S. Murthy ¹

Affiliations
1 Deepwater Exploration Group, EBG, Mumbai Regional Business Centre, ONGC, Mumbai, IN

Abstract

The sedimentary patch in Konkan deepwaters, located west of the Konkan continental shelf contains over 3 km thick sediments. Based upon the interpretation of over 11,000 line km of seismic data, gross basin configuration model has been worked out. The basin floor at the base of Tertiary is differentiated into a series of rift zones containing synrift sediments. These zones are superimposed by post-rift sediments deposited as a result of flexurally distributed thermal subsidence. Therefore, the sediments in the basin are divisible into three distinct mega-seismic packages denoting three major tectonic habitats of the evolution of the Konkan continental margin. Based upon the basinal configuration of each mega-seismic package in space and time, tectono-sedimentary evolution of the continental margin is brought out with an assessment of hydrocarbon prospects.

Keywords

Marine Geophysics, Seismic Data, Rift Tectonics, Hydrocarbon Prospects, Western Indian Continental Shelf.

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R. K. Kar ¹, A. K. Srivastava ¹, N. C. Mehrotra ², S. N. Swamy ², R. S. Rawat ²

Affiliations
1 Birbal Sahni Institute of Palaeobotany, 53 University Road, Lucknow - 226 007, IN
2 Keshab Dev Malviya Institute of Petroleum Exploration, Oil and Natural Gas Corporation Limited, Kaulagarh Road, Dehra Dun - 248 195, IN

Abstract

No Abstract.

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A. K. Srivastava ¹, Deepa Agnihothri ¹

Affiliations
1 Birbal Sahni Institute of Palaeobotany, 53, University Road, Lucknow – 226 007, IN

Abstract

Plant fossils collected from the Bijori Formation of Satpura Gondwana Basin are described in detail from the type locality as well as from other exposures. The assemblage is dominated by glossopterid remains with few specimens of pteridophyte of Glossopteris flora viz. Santhalea bansloiensis, Neomariopteris sp., Trizygia speciosa and 20 species of Glossopteris viz., G. angustifolia, G. searsoliensis, G. tenuifolia, G. surangei, G. kamthiensis, G. utkalensis, G. syaldiensis, G. sp. cf G. zeilleri, G. stricta, G. bosei, G. intermittens, G. stenoneura, G. gopadensis, G. wilkinsonii, G. retifera, G. conspicua, G. mohudaensis, G. browniana, G. communis, G. indica, Vertebraria indica, dispersed seeds of Cordaicarpustype and equisetalean axes with or without nodes and internodes.

Bijori bed is correlated with the Raniganj Formation of Damodar Basin but present study indicates that floristically it is distinct. Plant fossils of Raniganj are represented by large size species of Glossopteris with fair representation of arthrophytes and ferns where as, Bijori Formation contains narrow shaped small sized species of Glossopteris and shows poor record of pteridophytes. It has been observed that the assemblage of Bijori is comparable with the plant fossil assemblages of non-coaliferous beds of Kamthi and Pachhwara Formations of Mahanadi, Wardha and Rajmahal Basins which are also considered younger than Raniganj Formation. The occurrence of different types of plant fossils beyond the limit of coal-bearing Raniganj Formation in Bijori, Kamthi and Pachhwara Formations signifies the closing chapter of Permian Glossopteris flora in Peninsular India with the continuation of some forms in the lower Triassic beds.

The non- existence of Dicroidium-pinnule in present assemblage rules out its faithful association with the Triassic flora.

Keywords

Plant Fossils, Bijori Formation, Satpura Basin, Madhya Pradesh.

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B. P. Singh ¹, A. K. Srivastava ¹

Affiliations
1 Department of Geology, Banaras Hindu University, Varanasi - 221 005, IN

Abstract

Late Paleocene-middle Eocene Subathu Formation represents the earliest deposits of the western Himalayan foreland basin. A large part of this formation is comprised of impure limestone and grey shale intercalations. The limestones contain sole marks, intraformational conglomerates, hummocky cross stratification and wave ripples. The occurrence of sole marks suggests that they are developed by the unidirectional currents at the initial phase of the storm that resulted erosion and subsequent deposition. The intra-formational limestone conglomerate also suggests erosion of the earlier deposited limestone hard grounds as a consequence of storm associated transgression. The hummocky cross stratification formed by the oscillatory flows during the long-shore littoral drift. The depth of formation of the hummocky cross stratified limestone facies was less than 40 m and most likely deposited between shore-face to backshore regions of the gulf similar to present day Persian Gulf. The identification of deeper facies (shelf facies) from Pakistan and coastal facies from India suggest that the gulf was open from the west and closed from the east.

Keywords

Hummocky Cross Stratification, Tempestites, Himalayan Foreland Basin, Subathu Formation, Northwest Himalaya.

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