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

M. S. Srinivasan ¹

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

Abstract

No Abstract.

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M. S. Srinivasan ¹, D. N. Singh ¹

Affiliations
1 Department of Geology, Banaras Hindu University, Varanasi 221005, IN

Abstract

The following five new species of benthic foraminifera are described and illustrated from the Neogene sequence of Little Andaman Island, Bay of Bengal: Bulimina andamanica* , Cibicides hochstetteri* , Pararotalia geei, Fursenkoina indica, Ehrenhergina schwageri. Observed stratigraphic ranges are given for each species. All the new species described occur associated with deepwater assemblages characteristic of lower to middle bathyal depths. Those marked with an asterisk have proved useful, as zonal markers in the Andaman Sea region.

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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, B. K. Chatterjee ¹

Affiliations
1 Department of Geology, Banaras Hindu University, Varanasi, IN

Abstract

Carbonate rocks are widespread on the Andaman-Nicobar Islands, northern Indian ocean, ranging in age from Early Miocene to Pleistocene. Lithologically they range from deep water to shallow watcr calcarenites.

Thin section analysis of the limestones has revealed the following major lithofacies: lithic foraminiferal-algal grainstone-packstone; lithic foraminiferal-algal wackstone-mudstone; volcanoclastic packstone-wackstone/radiolarian cherts; foraminiferal packstone; coralgal boundstone and coarse lithic foraminiferal-algal-molluscan packstone grainstone. They exhibit sequential changes in their fabrics, biogenic and clastic constituents. Depths of deposition ranged from high energy, shallow neritic (lithic foraminiferal- algal grainstone-packstone facies) at the begnining of Early Miocene to progressively lower bathyal marked successively by lithic foraminiferal-algal wackstone-mudstone, volcanoclastic packstone-wackstone and radiolarian chert facies. The sudden influx of glass shards and tephras in thc later Early Miocene suggests that progressive deepening of the basin occurred contemporaneously with explosive volcanism in neighboring areas. During this interval of basinal subsidence, the limestones received abundant argillaceous material from subaerial erosion of nearby volcanic terrain. Gradual reduction in the frequency of glass shards and pumice from Middle Miocene (Ongeian Stage) onwards indicates culmination of volcanic eruptions and basinal stability. Gradual shallowing to subtidal and patch reef (Coralgal facies) environments began to form from the Middle Miocene onwards at Little Andaman, Havelock, Nicholson and other islands. However, deep basinal conditions prevailed during the Late Miocene to Early Pliocene at Neill, Sir Hugh Rose and Car Nicobar Islands. These different conditions may be attributed to tectonism in the Andaman sea region which occurred during the close of Middle Miocene. Thereafter, younger limestone facies of Plio-Pleistocene age, reflect a shoaling upwards to probable intertidal conditions due to rapid infilling and vertical uplift of the basin floor.

No hydrocarbons have been observed in the limestone sequences. However, the regional stratigraphic and petrographic studies reveal the presence of potential reservoir rocks in the Ongeian-Havelockian limestones of Middle Miocene age on the Andaman-Nicobar Islands.

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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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M. S. Srinivasan ¹

Affiliations
1 Banaras Hindu University, Banaras, IN

Abstract

No Abstract.

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M. S. Srinivasan ¹

Affiliations
1 Banaras Hindu University, Varanasi, IN

Abstract

No Abstract.

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Anil K. Gupta ¹, M. S. Srinivasan ²

Affiliations
1 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur 721302, IN
2 Department of Geology, Banaras Hindu University, Varanasi 221005, IN

Abstract

Quantitative data of Late Miocene deep-sea benthic foraminifera from the tropical Indian Ocean DSDP Site 214 have been combined with oxygen and carbon isotope values to understand the history of deep thermohaline circutation in the Indian Ocean. The important faunal changes include a significant increase in Uvigerina proboscidea percentages at c. 8.S to 7.5 Ma and during 6.2 to 5.2 Mat reaching their maximum values at the Miocene/Pliocene boundary. The increase in U. proboscidea percentages are accompanied by decreasing abundances of Bulimina alazanensis. Obicides kullenbergi, and C. wuellerstorfi. and lower values of H (S) and E'. The δ ¹⁸0 values are, in general, higher during these intervals While δ¹³C values show a decreasing trend. The interval between 7.5 and 6.2 Ma is marked by a major increase in B. alazanensis which coincides with slightly higher δ^l3C and lower δ¹⁸0 values. C. kullenbergi and C. wuellerstorfi. interestingly, reveal significant variations with higher values before Chroo - 6 Carbon Shift at about 6.2 Ma and a prominent peak immediately preceding the shift, but remain low and less variable following the shift during the remainder of the Late Miocene as do the δ ¹³C va1ues. The well-known Late Miocene Chron - 6 negative carbon shift is marked by significantly higber U. proboscidea percentages, and lower C. ku/lenbergi, C. wuellerstorfi and B. alazanensis values. Out data support the hypothesis that the shift was caused by excess organic carbon input to the system. and higher rate of upwelling and ocean productivity. The Miocene/ Pliocene boundary marks a warming event and is typified by highest percentages of U. proboscidea and Osanguiaria culter, lighter δ¹⁸0 and lighterδ¹³C values, and lowest values of H(S) and E'. The sediment accumulation rates were remarkably higher at the Miocene/Pliocene boundary. These events reflect high rates of surface productivity intensified by strong upwelling.

Keywords

Foraminifera, Miocene, Indian Ocean.

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M. S. Srinivasan ¹

Affiliations
1 Department of Geology, Banaras Hindu Univusity, Varanasi-221005, IN

Abstract

No Abstract.

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A. D. Singh ¹, M. S. Srinivasan ²

Affiliations
1 Marine Geology Division, School of Marine Sciences, Cochin University of Science and Technology, Cochin 682016, IN
2 Departrnent of Geology, Banaras Hindu University, Varanasi 221005, IN

Abstract

Qualitative and quantitative planktic foraminif∼raal nalyses of the Central Indim Ocean DSDP Sites 237 and 238 provided 34 important events during the Neogene. A comparison of the chronoIogica1 succession of ihese planktic foraminiferal events, with the other tropical Indian Ocean and Southwest Pacific DSDP Sites reveals remarkable similarity. Therefore, these Neogene foraminiferai events [First Appearance (FA) and Last Appearance (LA)] are considered as synchronous within the tropical Indo-Pacific except Gq. dehiscens LAD, Gr. margaritae FAD, range of Gr. tumidaflexuosa, Gr. crassaformis FAD, Gr. truncatulinoides FAD, and Gs. obliquusLAD, which are diachronous reflecting their paleobiogeographic control. Stratigraphic ranges of planktic foraminifera enabled recognition of 20 zones from the late Early Miocene to Pleistocene.

Two hiatuses (NH3 at Site 238 and NH4 at Site 237) associated with severe carbonate dissolution were identified. These hiatuses havealsobeen recordedatabout the same stratigraphic intervals in several deep sea sections in the Pacific and represent an important oceanographic event, useful for inreroceanic correlation.

Keywords

Micropalaeonloiogy, Planktic Foraminifera, Central Indian Ocean, Neogene.

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V. Sharma ¹, M. S. Srinivasan ², A. K. Mahapatra ¹

Affiliations
1 Department of Geology, University of Delhi, Delhi 110 007, IN
2 Department of Geology, Banaras Hindu University, Varanasi 221 005, IN

Abstract

The Early Miocene sequences of North Passage Island iu the Andaman Sea have been studied for their siliceous and calcareous microfossil assemblages. 95 species of radiolaria and 27 species of planktonic foraminifera belonging to these two major groups of microfossils have been documented. An integrated radiolarian ancl planktonic foraminifera1 biostratigraphy is presented.

Keywords

Radiolaria, Planktonic Foraminifera, Biostratigraphy, Micropaleontology, Early Miocene, Andaman-Nicobar Islands.

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M. S. Srinivasan ¹, V. Sharma ¹

Affiliations
1 Department of Geology, Banaras Hindu University, Varanasi, IN

Abstract

The paper gives a complete stratigraphic sequence of Car Nicobar strata for the first time since the work of Schwager. The Sawai Bay formation (consisting of a mudstone member and a limestone member) and the Malacca limestone formation belonging to Archipelago Group are proposed with their type localities defined at Car Nicobar island. Based on the known stratigraphic ranges of planktonic foraminifera, the following three zones are distinguished in ascending order: (1) Globorotalia tumida flexuosa zone, (2) Globigerina nepenthes zone, and (3) Globorotalia multicamerata-Pulleniatina obliqueloculata (s.s.) zone. An Early to Middle Pliocene age is assigned to Schwager's Car Nicobar foraminifera based on planktonic foraminiferal evidence. A comparison of the zonation of Car Nicobar island with zones proposed by Banner and Blow shows that Banner and Blows' sequence is most applicable, and is used in the present work as a basis for comparison.

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M. S. Srinivasan ¹

Affiliations
1 Department of Geology, Banaras Hindu University, Varanasi - 221005, IN

Abstract

No Abstract.

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Ajai Kumar Rai ¹, M. S. Srinivasan ², Abhayanand Singh Maurya ¹

Affiliations
1 Department of Earth and Planetary Sciences, Nehru Science Centre, University of Allahabad, Allahabad 211 002, IN
2 Department of Geology, Banaras Hindu University, Varanasi - 221 005, IN

Abstract

This study quantitatively analyzes Pliocene-Pleistocene benthic foraminifera from DSDP Site 238 in the central Indian Ocean. A Q-mode factor analysis of 28 most abundant species defines three significant faunal assembiages reflecting different environmental characteristics. The Cibicides wuellerstorfi-Oridorsalis umbonatus assemblage (Factor I ) represents well oxygenatcd bottom watcrs with active currents and intermediate to low supply of organic matter. The Uvigerina proboscidea assemblage (Factor 2) indicates a continuously high flux of organic matters to the sea floor in response to increased surface water productivity. The Nuttallides umbonifera assemblage (Factor 3) is associated with Antarctic Bottom Water (AABW) and reflects cold, oligotrophic, increased carbonate corrosiveness and high oxygen concentration.

In most of the past 5 Ma (i.e. 5-4.2 Ma, 2.8-1.8 Ma and 1.2 Ma to Recent) the dominant occurrences of Cibicides wuellerstorfi-Oridorsalis umbonatus assemblage represent active bottom water currents with more ventilation and relatively low trophic levels reflecting the influence of NADW at abyssal depths in the central Indian Ocean. The early Late Pliocene (c. 3.6-2.8 Ma) and Early Pleistocene (c. 1.8-1.2 Ma) are two significant intervals of prominent faunal change, which indicate entirely different deep-sea conditions. The prominent occurrence of Nuttallides umbonifera assemblage during 3.6-2.8 Ma reflects cold, corrosive and well-oxygenated bottom waters possibly in response Lo increased flow of AABW towards the central Indian Ocean at abyssal depths. The Early Plcistocene (c. 1.8-1.2 Ma) is characterized by distinct occurrence of the Uvigerina proboscidea assemblage reflecting higher surface produc6vity. The widespread, intensified monsoon system during Early Pleistocene causes increased upwelling and higher surface productivity, which also enhanced the supply of organic carbon to the ocean floor.

Keywords

Benthic foraminiferal record, Antarctic Bottom Water, Monsoonal activity, DSDP Site 238, Central Indian Ocean.

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Ajai K. Rai ¹, M. S. Srinivasan ²

Affiliations
1 Department of Earth and Planetary Sciences, Nehru Science Center, Allahabad University, Allahabad - 211 002, IN
2 Department of Geology, Banaras Hindu University, Varanasi - 221 005, IN

Abstract

In the present study four distinctive species of the genus Favocassidulina are recorded from the Neogene deep sea sequences of seven DSDP Sites (Legs 22,23 and 24) in the Indian Ocean. Detailed systematic descriptions and stratigraphic ranges of these species in the Indian Ocean have been provided. In addition, on the basis of quantitative faunal analysis, an attempt has been made to assess the ecological significance of the genus Favocassidulina. Species of this genus are largely confined to lower bathyal and abyssal depths and exhibit restricted occurrences in Indian and, Pacific Oceans only. The intervals of higher relative abundances of genus Favocassidulina during Neogene possibly reflect low organic carbon input in the bottom waters.

Keywords

Neogene, Benthic Foraminifera, Favocassidulina, Palaeoccology, Indian Occan.

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S. Kanjilal ¹, M. S. Srinivasan ¹

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

Abstract

The presents paper reports large sized internal moulds of seven new and exotic bivalves from the Miocene rocks of Little Andaman Island in the Bay of Bengal. The fauna (comprising five taxa) include one new subfamily (Trapezicardiinae n. suhfam.), one new genus (Trapezicardiwn n. gen.) one new subgenus (Megalaevicardium n. subgen. under Laevicardium Swainson), and three new species [viz., Glycymeris (Glycymerita) gigantica n. sp., T. laiensis. n. gen. and n. sp., and L. (M.) hutbayensis n. subgen. and n. sp.].

Keywords

Bivalves, Miocene, Little Andaman Island, Bay of Bengal.

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