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

A. Nallapa Reddy ¹, B. C. Jaiprakash ¹, K. V. Bhaktavatsala ¹

Affiliations
1 Oil and Natural Gas Corporation Ltd., 3, First Lane, N.H. Road, Chennai - 600 034, IN

Abstract

Quantitative foraminiferal data in a temporal succession identifies a type 1 third order Miocene depositional sequence (Ravva Formation/Sequence) of sechron ∼6 Ma in Godavari shelf area. This sequence has developed as a shelf delta build-up. This sequence is divided into a transgressive systems tract (TST) and a highstand systems tract (HST) separated by a maximum flooding surface (MFS), based on faunal frequency trends. The TST plays host to all reservoir facies, suggesting that the sand depocentres have migrated landward, concurrent with progress of the transgressive phase. The Ravva Sequence is bounded below by a type 1 unconformity spanning ∼7 Ma across the Oligocene-Miocene boundary. This unconformity surface hosts reservoir facies in well GS-AE-D. The sequence is bounded above by a type 1 unconformity of ∼10 Ma across the Miocene-Pliocene boundary. This unconformity is a diachronous surface produced by a progradational highstand systems tract. This surface represents possibly the only period during the Neogene, where large quantities of middle to late Miocene sediments may have by- passed the shelf. These by-passed sediments, according to the proposed sequence depositional model, should occur as Iowstand systems tract deposits (shelf edge deltas and fan deposits).

Keywords

Sequence Stratigraphy, Sequence Boundary, Systems Tracts, Maximun Flooding Surface, Sechron, Miocene, Godavari Offshore.

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K. Satyanarayana ¹, A. Nallapa Reddy ¹, B. C. Jaiprakash ², L. Chidambaram ¹, Shekhar Srivastava ¹, D. K. Bharktya ¹

Affiliations
1 Regional Laboratory, ONGC, Cauvery Basin, Chennai, IN
2 ONGC, Forward Base, Cauvery Basin, Karaikal, IN

Abstract

Analysis of tsunami sediments collected along Karaikal to Nagapattinam beaches revealed that all the sediments are of silty/Clay lithology consisting of predominantly montomorillonite, chlorite with rare presence of glauconite. Well preserved foraminiferal tests including long spines of Asterorotalia trispinosa and Ammonia dentata indicate no grain to grain abrasion during transportation of sediments. The fine grained lithology and foraminiferal assemblage data strongly point that there was only transfer of energy through tidal waves and there was no reworking of oceanic sediments.

Keywords

Tsunami, Foraminifera, Clay Minerals, Beaches, Tamil Nadu Coast.

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A. Nallapa Reddy ¹, K. Satyanarayana ¹, K. V. Bhaktavatsala ¹, K. Narasimha ¹, M. Nagaraj ¹

Affiliations
1 Regional Laboratory, ONGC Ltd., N.H. Road, Chennai - 600 034, IN

Abstract

Detailed chronostratigraphic biodatums and lithofacies in combination with correlative seismic horizons recognized two 3^rd order depositional sequences designated as Sequence 1 and Sequence 2 in stratigraphic order within Miocene in KD field. The biostratigraphic correlation has brought out that the Sequence 1 in shelf well GS-AD is sandrich and bounded by unconformable sequence boundaries, whereas coeval sequence in slope wells KDA and KDB, bounded by correlative conformities are dominated by clay rich system deposited during highstand sea-levels in earlymiddle Miocene. The clays are planar bedded with glauconite and pyrite nuggets with abundant deepwater benthics in association with shelf derived foraminifera, inferring that these clays were derived into intraslope basins mainly as debris flow/slump process. The Sequence 2 in wells KDA and KDB is represented by multiple sands with mudstone alternations, deposited during lowstand Sea-Levels. Biofacies are mixed with dominantly shelf derived benthics and the tests are commonly broken, abraded and occasionally ferruginised, suggesting reworking into intraslope basins as a result of relative Sea-Level fall during middle and late Miocene. The occurrence of abundant Paleocene to early Miocene dinoflageIlate cyst assemblage are also suggesting reworking process into upper slope by network of active channel system and were redeposited by Gravity-Flow processes into intraslope basins. The present study indicates each intraslope basin acting as an independent petroleum system and matured organic rich Paleogene beds lying at the bottom are contributing hydrocarbons to middle Miocene reservoirs through active growth fault system.

Keywords

KD-Structure, Sequence Stratigraphy, Systems Tracts, Depositional Setting, Krishna-Godavari Basin.

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R. Nagendra ¹, R. Kannan ¹, R. Bhavani ¹, P. Shanmuga Johari ², A. Nallapa Reddy ³, B. C. Jaiprakash ⁴

Affiliations
1 Center for Geoscience and Engineering, Anna University, Chennai - 600 025, IN
2 Department of Earth Sciences, University of Windsor, Windsor, Ontario, CA
3 Regional Geology Laboratory, Oil and Natural Gas Corporation Ltd , Chennai - 600 034, IN
4 Forward basin, ONGC, Tnpura Project, Badarghat Complex, Agarthala - 799 014, IN

Abstract

Twenty-four Pleistocene-Holocene deepwater benthic foramimferal species were identified based upon taxonomic criteria from a 26 m core sample collected during Academik Aleksandr Sidorenko cruise. The quantitative data of benthic foraminifera) taxa is treated statistically using multi vanate (both factor and cluster) techniques to understand the relationship between species assemblages and environmental parameters. The temporal distribution of samples in cluster II closely coincides with the distribution of higher loading values of factor 1 Similar associations were identified for cluster III with factor 2 and cluster IV with factor 3. However the faunal relative abundances along with %. Total Organic Content (TOC) values broadly divides the core into two environmentally significant zones viz, Zone 1 (between 1322 6m and 1321 6 m) which is characterised by high abundance of Cassiduhna cannata followed by Pullenia bulloides and Hoeglundina elegans having positive relationship with low TOC values ranging from 0 12 to 1 14 and Zone 2 (between 1321 6m and 1320 1 m), which is characterised by high percentages of TOC values ranging from 1 32 to 2 52, whereas Buhmina aculeata shows maximum abundance followed by Bohvina robusta, Cibiadoides kullenbergi and Osangulana culter, suggesting that these species prefer high nutrient environment.

Keywords

Benthic Foraminifera, Pleistocene, Holocene, Tuticonn, Bay of Bengal.

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R. Nagendra ¹, R. Raja ¹, A. Nallapa Reddy ², B. C. JaiPrakash ³, R. Bhavani ¹

Affiliations
1 Centre for Geoscience and Engineering, Anna University, Chennai - 600 025, IN
2 Regional Geology Laboratory, Oil & Natural Gas Corporation Ltd., Chennai - 600 034, IN
3 Geology Division, ONGC, Tripura Project, Badarghat complex, Agartala - 799 014, IN

Abstract

No Abstract.

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R. Nagendra ¹, G. Nagendran ¹, K. Narasimha ², B. C. JaiPrakash ³, A. Nallapa Reddy ²

Affiliations
1 Centre for Geosciencc and Engineering, Anna University, Chennai - 600 025, IN
2 Regional Geology Laboratory, Oil & Natural Gas Corporation Ltd., Chennai - 600 034, IN
3 Geology Division, ONGC, Tripura project, Badarghat complex, Agartala - 799 014, IN

Abstract

A sequence stratigraphic framework is worked out for the first time for the Dalmiapuram Formation exposed in Kallakudi quarry near Kallakudi village in Tiruchirapalli District. Thc complete lithological succession of this formation is designated as 'Dalmiapuram Sequence' of latest Albian - Cenomanian age and consists of grey shale, coral/algal limestone and bedded biostromal limestone and marl in ascending order. Grey shale rests unconformably ovcr thc Archaean basement. This contact forms the lower sequencc boundary of Dalmiapuram Sequence. The middle lithounit, the coral algal limestone rests ovcr grey shale. This unit abruptly grades into bedded limestone/marl alternations. This abrupt termination of coral algal limestone may be due to relative sea level rise and possibly this surface represents 'drowning unconformity'. The upper lithounit, which has alternating bands of biostromal limcstonc and marl, might indicatc cyclic carbonate precipitation (?Milankovich cycles). This unit is unconformably overlain by Neogene Cuddalore sandstone. This unconformity surface represents the upper boundary of the sequencc. The entire Dalmiapuram Sequence appears to have been deposited as Transgressive Systems Tract (TST) dcposit and got exposed as a result of basinal rise.

Keywords

Sequence Stratigraphy, Dalmiapuram Sequence, Albian-Cenomanian, Kallakudi, Tamil Nadu.

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A. Nallapa Reddy ¹, K. Yadagiri ¹

Affiliations
1 Oil and Natural Gas Corporation Ltd., No.3, First lane, N.H. Road, Chennai-600 034, IN

Abstract

Two relatively uninterrupted sequences spanning the Cretaceous-Tertiary boundary (KTB) arc present at two sites, namely Ammapettai-A (AMT-A) in Thanjavur sub-basin and Anandathandavapuram-A (ATP-A) in Ariyalur- Pondicherry sub-basin in Southern India. A total of 28 benthic foraminiferal species were identified at the generic or specific level. The occurrence of Nuttallides truempyi, Gavelinella beccariiformis, Bulimina trinitatensis and agglutinated foraminifera across KTD suggests that the palcobathymetry was >500m, and that deep sea benthic foraminifera were not severely affected by the KTB event. However, changes in foraminiferal relative abundances and their morphotypes were noticed across KTB and were related to changes in supply of organic fluxes to the basin floor. The clay mineral assemblages across KTB at the two sites appear to be little different. The high abundance of kaolinite clay close to the KTB at site AMT-A, may be attributed to progradational or shifting of depositional pattern.

Keywords

Benthic Foraminifera, K-T Boundary, Clay Mineralogy, CauvEry Basin.

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P. K. Kathal ¹, R. Nagendra ², R. Raja ², A. Nallapa Reddy ³, B. C. Jayaprakash ⁴, R. Bhavani ²

Affiliations
1 Centre of Advanced Study in Geology, Dr. H.S.G. University, Sagar - 470 003, IN
2 Centre for Geoscience and Engineering, Anna University, Chennai - 600 025, IN
3 Regional Geology Laboratory, Oil and Natural Gas Corporation Ltd., Chennai - 600 034, IN
4 Geology Divsion, ONGC, Tripura Project, Badarghat Complex, Agartala - 799 014, IN

Abstract

No Abstract.

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