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

M. S. Srinivasan ¹, Alok Dave ²

Affiliations
1 Graduate School of Oceanography, University of Rhode Island, Kingston, R. I. 02881, US
2 Department of Geology, Banaras Hindu University, Varanasi, IN

Abstract

The paper briefly describes the sequence of Cenozoic marine sediments that occur on Long Island, Middle Andaman, northeastern Indian Ocean. The stratigraphic sequence recognized is based mainly on the study of smaller foraminifera from measured sections in the western, and eastern parts of the island. The occurrence of Neogene strata on Long Island has been known for some time but until now Paleogene rocks have not been reported from Long Island or any of the other islands east of the main Andaman ridge. The Paleogene strata represented by the Conglomerate and Grit Formation (Port Blair Series) occur only in the northern part of the island, forming the basement upon which the Neogene sediments were deposited. The Neogene strata of Long Island are represented by Inglis Formation (Early Miocene), Long Formation (Late Miocene) and Guitar Formation (Pliocene). The Long Formation yielded rich foraminiferal assemblages, while the recovery from the other two formations was poor.

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M. S. Srinivasan ¹, Gail Lombari ², Alok Dave ¹

Affiliations
1 Department of Geology, Banaras Hindu University, Varanasi 221005, IN
2 Graduate School of Oceanography, University of Rhode Island, Kingston, RI 02881, US

Abstract

This contribution is the first of the series of investigations on integrated radiolarian and planktonic foraminiferal biostratigraphy of the Andaman-Nicobar region. Fifty species of radiolaria and thirty-one species of planktonic foraminifera have been recorded from the Early Miocene sequence exposed at Piu Bay, Colebrook Island, Andaman Sea (Northern Indian Ocean). The planktonic foraminiferal assemblage is referable to the Upper Catapsydrax dissimilis Zone and Lower Catapsydrax stainforthi Zone representing the interval from the Upper Andamanian to Lower Jarawaian Stages (Lower Archipelago Series). The radiolarian assemblage is referable to the Stichocorys wolffii Zone which corresponds with Paleomagnetic Epoch 18 with an estimated age of 18.5 to 19.5 Ma. Comparison of radiolarian and planktonic foraminiferal assemblage in the Piu Bay section with Deep Sea Drilling Project data indicate an Early Miocene age of 18.5 to 19.5 Ma.

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D. S. N. Raju ¹, B. C. Jaiprakash ¹, Arun Kumar ¹, R. K. Saxena ¹, Alok Dave ¹, T. K. Chatterjee ¹, C. M. Mishra ¹

Affiliations
1 Geological Laboratories, KDM Institute of Petroleum Exploration, ONGC, Kaulagarh Road, Dehra Dun - 248195, IN

Abstract

The latest Paleontological data suggest that the duration of Deccan trap eruption in Krishna-Godavari basin varies from place to place and could be anywhere between <0.5 Ma and 6 Maacross KTB. Three groups of fossils viz., Planktic foraminifera, Nannoplanktics and Dinoflagellate cysts suggest that the initiation of volcanism was during latest Maastrichtian within the upper part of Abathomphalus mayaroensis Zone, Micula murus Zone and Triblastula utinensis Zone between 67 and 66.5 Ma. There are conflicting evidences in dating the upper age limit of the volcanics probably due to diverse methods employed in calibration of forarniniferal and nannoplanktic scales or selective retrieval of very small sized planktics of zones P0 and P1 in well cuttings.

Keywords

Micropalaeotogy, Deccan Volcanism, Age, Krishna-Godawari Basin.

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Alok Dave ¹, T. K. Chatterjee ¹

Affiliations
1 Paleontology Laboratory, KDMlPE, ONGC, Kaulagarh Road, Dehra Dun-248 195, IN

Abstract

In the Post-Vindhyan times, major marine transgressions covered the areas of Kutch and Rajasthan, including the Jaisalmer Basin during Jurassic, although minor Permian transgressions are also known. These events could be documented from the well known exposures of Kutch and Rajasthan which entombed classic Cephalopod fauna. The foraminiferal components of Kutch Mesozoic were catalogued by Pandey and Dave (1993), recognizing 13 benthic foraminiferal biozones, establishing 8 chronostratigraphic units (stages).

Within the outcropping marine Middle-Upper Jurassic succession of Jaisalmer, seven benthic foraminiferal zones have been recognized and correlation with Kutch Mesozoic established. However, the succession is interrupted by five hiatuses during - (1) Upper Bathonian, (2) Upper Callovian - Lower Oxfordian, (3) Upper Oxfordian - Lower Kimmeridgian, (4) Middle Kimmeridgian and (5) Upper Kimmeridgian - Lower Tithonian.

Trangressive events during Lower Bathonian, Lower Callovian, Middle - Upper Oxfordian and Lower Kimmeridgian with intervening regressive pulses are also recorded.

Badian, Charian, Dhosaian, Katrolian and Umiaian stages of Kutch ranging in age from Bathonian to Tithonian are recognized.

Keywords

Biostratigraphy, Micropaleontology, Foraminifera, Jurassic, Jaisalmer, Rajasthan.

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Alok Dave ¹

Affiliations
1 Palaeontology Laboratory, K.D. Malaviya Institute of Petroleum Exploration, ONGC, Dehradun - 248 195

Abstract

Neogene planktic foraminiferal events and biostratigraphy of four deep well sections viz. D1-A-1, SS-1, R-13-1 and D-4-1 in the Bombay Offshore Basin have been established. A pronounced and regiona lunconformity separates the post-Miogypsina (post Zone N10 or N12, Middle Miocene) clay/claystone succession from the underlying carbonates. In most of the studied wells the hiatus covers a time span of 6.5 Ma (or 9.7 Ma) involving part of Middle Miocene and entire Late Miocene except in well D-4-1 where its span is greatly reduced. Three planktic foraminiferal datums viz. LAD of Globigerina nepenthes (3.78 Ma), LAD of Dentoglobigerina altispira (2.6 Ma) and LAD of Globigerinoides fistulosus (1.6 Ma) have been demarcated in the Pliocene. A comparison of these biochronologic datums with those recorded from the DSDP sites in northern Indian Ocean is made. The delayed Last Occurrence of Globoquadrina dehiscens in Bombay Offshore is attributed to its reworking in Pliocene.

Keywords

Biostratigraphy, Neogene, Foraminifera, Bombay Offshore Basin.

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