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

Prabha Pandey ¹, R. S. Rawat ²

Affiliations
1 National Geophysical Research Institute, Hyderabad - 500007, IN
2 Wadia Institute of Himalayan Geology, Dehra Dun - 248001, IN

Abstract

Pre-Himalayan granites are important in the study of evolution of Himalaya. Amritpur Granite Series (AGS) in the Kumaun Lesser Himalaya is one such Pre-Himalayan, Precambrian granite and is of three types, viz. Porphyritic Amritpur Granite (PAG), Equigranular Amritpur Granite (EAG) and Amritpur Porphyry (AP). The field, mineralogical and geochemical characteristics of AGS are consistent with those of S-type granites. The AGS is peraluminous with A/CNK (>1.1) and high normative corundum. besides high (⁸⁷Sr/⁸⁶Sr) ratio of 0.7117+0.0044. Major and trace element geochemistry of AGS indicates a syn-collisional regime and anatexis associated with pre-Himalayan collision during Precambrian times. The melt produced by anatexis has intruded into the Precambrian Bhimtal-Bhowalj Formation.

Keywords

Geochemistry, Tectonic Setting, S-Type Granites, Kumaun Himalaya.

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N. C. Mehrotra ¹, S. N. Swamy ¹, R. S. Rawat ¹

Affiliations
1 KDM Institute of Petroleum Exploration, Oil and Natural Gas Corporation Limited, Dehra Dun -248 195, IN

Abstract

A reworked Carboniferous palynofossil assemblage from the subsurface sections of the Early Eocene basal clastics of Panna Formation, Bombay offshore basin has been discovered. This assemblage is recorded at various stratigraphic levels of the studied well sections along with the indigenous Early Eocene dinoflagellate cysts and sporepollen taxa. Initial studies have suggested more than one possibility of explaining the provenance of reworked sediments containing the Carboniferous palynofossils. One possibility is that these might have been derived from the erosion of Early Palaeozoic sediments present in the Deccan volcanic province. Alternatively, these sediments could result from long distance transport of reworked material from Saudi Arabia-Africa region in the west which were deposited in the Bombay offshore region during Early Eocene. Available evidences, for and against these two possibilities are discussed. Our studies show that the Carboniferous reworked assemblage is confined to the Heera-Bassein block. The reworking in the Panna Formation might have taken place by palaeorivulets cutting through the thin Deccan Trap flows, exposed in the faulted blocks. A model explaining the mechanism of reworking has been presented. Organic matter studies indicate the presence of mature sediments below the Deccan Trap, which suggest a possible hidden basin to be a new exploration target for hydrocarbon.

Keywords

Carboniferous, Palynofossils, Panna Formation, Bombay offshore basin, Hydrocarbon.

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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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