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

S. Ramasamy ¹, J. Madhavaraju ¹, J. Armstrong Altrin Sam ¹

Affiliations
1 Sedimentology Lab, Department of Geology, School of Earth and Atmospheric Sciences, University of Madras, Guindy Campus, Chennai 600 025, IN

Abstract

Recent field study of Gondwana sediments in the Palar basin near Chennai brings to light the occurrence of assorted size of boulders of extraneous source in argillaceous siltstones. These boulders are regarded as glacial in origin. It is interpreted that icebergs carried such boulders into a pro-glacial lake. Melting of the icebergs resulted in dropping of boulders into the depositional environment. The present study discusses the depositional environment and paleoclimate that prevailed during the deposition of these exotic boulders.

Keywords

Depositional Environment, Paleoclimate, Dropstones, Gondwana Sediments, Icebergs, Pro-Glacial, Palar Basin, Tamil Nadu.

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J. Madhavaraju ¹, S. Ramasamy ¹

Affiliations
1 Sedimentology Lab, Department of Geology, School of Earth and Atmospheric Sciences, University of Madras, Guindy Campus, Chennai - 600 025, IN

Abstract

Studies on the quartz grains of the Campanian-Maastrichtian sediments of the Ariyalur Group of Tiruchirapalli Cretaceous, Tamil Nadu, using Scanning Electron Microscope (SEM) have brought out nineteen distinct microtextures. They have been grouped into features based on their mode of origin. Of these, thirteen are of mechanical and five mechanical and/or chemical origin while one distinctly chemical. The quartz grains of the Ariyalur Group sediments show a wide range of conchoidal fractures, straight steps and arcuate steps formed during the liberation from the metamorphic and igneous source rocks. The microtextures - v's, pits, straight and curved scratches are characteristic of the marine environment. The frequency of these features is higher in the grains from the Sillakkudi, Kallankurichchi and Ottakkovil Formations. Rarity of these features on quartz grains from the Kallamedu Formation is suggestive of variation in transport and depositional conditions. It has been inferred from the microtextures that the source for the quartz grains in the Ariyalur Group sediments has been the nearby Precambrian crystalline basement.

Keywords

Sedimentology, Quartz Grains, Ariyalur Group, Microtextures, Depositional Environments, Tamil Nadu.

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J. Madhavaraju ¹, S. Ramasamy ¹

Affiliations
1 Sedimentology Lab. Department of Geology, School of Earth and Atmospheric Sciences, University of Madras, Guindy Campus, Chennai 600 025, IN

Abstract

Studies on calcium carbonate (CaCO₃), trace elements and rare earth elements were carried out on the Kallankurichchi Formation in order to understand the elemental behaviour in marine limestones of the Tiruchirapalli Cretaceous. Variation in EREE content between Sandy Fossiliferous Limestone (SFL) and Fossiliferous Limestone (FL) can be explained as due to the varying amounts of terrigenous material present in the limestones. PAAS (Post Archaean Australian Shale) normalised REE patterns and La_N/Yb_N ((La_Sample/La_Shale)/(Yb_Sample/Yb_Shale)) ratios suggest that the terrestrial rocks are the major source for REE in these limestones. The SFL and FL show negative Ce anomalies, with slight variation between these limestones. The negative correlation between CaCO₃ and Ce/Ce* values indicates that the observed Ce anomalies are not related to the CaCO₃ content in SFL and FL, whereas Ce/Ce* values show positive correlation with detrital elements implying that the observed variations in the Ce anomalies resulted from the variation in the terrigenous material supplied by the continental area. SFL and FL show low U/Th ratio and U content. Low U contents suggest that the oxic condition prevailed in the bottom water and sediment column during the deposition of Kallankurichchi Formation.

Keywords

Geochemistry, REE, Cerium Anomaly, U and U/Th, Oxic Environment, Tiruchirapalli Cretaceous, Tamil Nadu.

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S. Ramasamy ¹, Thingujam Shantikumar Singh ¹, J. Madhavaraju ², Gladwin Gnana Asir ¹

Affiliations
1 Department of Geology, School of Earth and Atmospheric Sciences, University of Madras, Guindy Campus, Chennai - 600025, IN
2 Estacion Regional del Noroeste, Instituto de Geologia, Universidad Nacional Autonoma de Mexico, Apartado Postal 1039, Hermosillo, Sonora 83000, MX

Abstract

The Maruvattur quarry section (Dalmiapuram Formation) is located near the Archaean-sedimentary boundary at the western margin of the Ariyalur-Pondicherry sub-basin. The lithofacies observed in the quarry include boulder-algal limestone and clastic limestone alternating with siltstone and claystone. This amply reveals that the depositional conditions fluctuated between carbonate facies to fine clastic facies. The coarse clastic materials are not found in the litho-sequence suggesting that the source area reached a peneplanation stage. This stage released only fine clastic materials to develop silty clay and siltstone lithologies. The clastic deposition was fine grained, hence it is interpreted that the depositional basin experienced a calm environment. The limestone units are mostly bedded types pointing out that the older biohermal limestone underwent erosion and redeposited as clastic limestone to form biostromal limestone. The clastic limestone has a few impressions of trace fossils suggesting the slower rate of sedimentation in a comparatively deeper marginal basin.

The Anaipadi river traverse representing Garudamangalam Formation indicates a variable lithological association along the dip direction. The claystone is the bottom most unit of this traverse. The clastic deposition is followed by a muddy carbonate phase, which further indicates a calm neritic environment that existed for sometime before deposition of subarkosic-Arkosic lithofacies towards the top in the traverse. The varied distribution of clastics has been useful to synthesise information on tectonics and sedimentation.

The trilinear plots such as Q, F, L (quartz, feldspar and lithic fragments), and Qm, K, P (quartz monocrystalline, potash and plagioclase feldspars) derived through modal analysis suggest a granitoid source area. The petrographic study and modal analysis suggest that the bottom quartz rich sequence formed in a semi-humid type climate, which gradually became semi-Arid as evidenced by the subarkosic-Arkosic sands towards upper level along the Anaipadi river traverse.

Keywords

Petrography, Geochemistry, Palaeoclimate, Depositional and Diagenetic Environments, Dalmiapuram and Garudamangalam Formations, Perambalur, Tamil Nadu.

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R. Nagarajan ¹, J. S. Armstrong-Altrin ², R. Nagendra ³, J. Madhavaraju ⁴, J. Moutte ⁵

Affiliations
1 School of Civil Engineering, Sastra University, Thanjavur - 61 3 402,, IN
2 Centro de Investigaciones en Ciencias de la Tierra, Universdad Autonoma del Estado de Hidalgo, Crudad Universitaria, Carretera Pachuca-Tulancingo km 4 5, Pachuca, Hidalgo 42 1 84, MX
3 Department of Geology, Anna University, Chennai - 600 025, IN
4 Institute do Geologia, Estacion Regional del Noroeste, Universidad Nacional Autonoma de Mexico, Apart Postal 1039, Hermosillo, Sonora 83000, MX
5 Centre SpiNC, Ecole des Mines, 158 cours Fauriel, F 42023, Sant-Etienne, FR

Abstract

Petrographic, major, trace, and rare earth element compositions of quartz arenites, arkoses, and siltstones of Neoproterozoic Rabanpalli Forrnation of Bhima Basin have been investigated to understand the provenance. The quartz arenites, arkoses, and siltstones have large variations in major element concentrations. For example, quartz arenites and arkoses contain the hlgher Si0₂ (average with one standard deviation being 97±1,73±2,respectively) and lower Al₂O₃ (0 95±0 4, 9 6±O 9, respectlvely) concentrations than siltstones (SiO₂=64±4, A1₂0₃=14±1), which is mainly due to the presence of quartz and absence of other Al-bearing minerals in relation with rock types. This is also supported by our petrography, since quartz arenites and arkoses contain significant amount of quartz relative to feldspar and lithic fragments. The observed low CIA values and A-CN-K diagram suggest that the sedimentary rocks of Rabanpalli Formation have undergone K-metasomatism.

The Co, Ni, Cr, Ba, Zr, Hf, and Th values are higher in siltstones than quartz arenites and arkoses. The EU/EU^*, (La/LU)_en, La/Sc, Th/Sc, Th/Co, Th/Cr, Cr/Th ratios, and Cr, Ni, V, and Sc values strongly suggest that these sediments were mainly derived from the felsic source rocks. This interpretation is also supported by the Th/Sc versus Sc bivariate and La-Th-Sc triangular plots. The rare earth element (REE) patterns of these rocks also support their derivation from felsic source rocks. Further more, these rocks exhibit higher LREE/HREE ratio (8±4) and a significant negative Eu anomaly (0 77±0 16), which indicate the felsic igneous rocks as a possible source rocks.

Keywords

Geochemistry, Paleoweathering, Provenance, K-Metasomatism, Sandstone, Bhima Basin, Karnataka.

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N. Gladwin Gnana Asir ¹, S. Ramasamy ², J. S. Armstrong-Altrin ³, J. Madhavaraju ⁴, V. Stephen Pitchaimani ²

Affiliations
1 People's Action for Development, 2/29, Sebastian Kovil Street, Vembar - 628 906, IN
2 Sedimentology Lab, Department of Geology, University of Madras, Chennai - 600025, IN
3 Centre de Investigaciones en Ciencias de la Tierra, Universidad Autdnoma del Estado de Hidalgo, Ciiidad Universitana, Carretera Pachuca-Tulancingo km. 4.5, Pachuca, Hidalgo, 42184, MX
4 Universidad Nacional, Autonoma de Mexico, Institute de Geologia, Estacion Regional del Noroeste, Hermosillo, Sonora, MX

Abstract

An 8.8m of consolidated core obtained below 20m of unconsolidated marly sediments near the Tuticorin coast was subjected to detailed stratigraphic, petrographic and geochemical analyses. A lithological succession with eight minor Litho-Units in ascending order has been established: Shell limestone, lower sandy shell limestone, calcareous conglomerate, middle sandy shell limestone, algal limestone, upper sandy shell limestone, calcareous sandstone and calcrete. The petrographic types are mostly the variants of wackestone, boundstone, arenite and calcrete. CaO is high in shell limestone, algal limestone and sandy shell limestone and proportionately SiO₂ is low in these litho-units. Algal limestone is enriched in MgO content, The conversion of high Mg-calcite to low Mg-calcite, aragonite inversion as well as mixed zone diagenetic setting resulted in depletion of both δ¹³C and δ¹⁸O, The petrographic evidence and assemblage of the juvenile gastropods, pelecypods, bryozoans, algae and benthic foraminifers suggest a fluctuating inner neritic to a moderately high saline lagoonal depositional environment. The absence of sparry calcite indicates an early marine to mixed zone diagenetic settings and the shell limestone unit experiences a moderate burial diagenesis while the upper units experience a shallow burial diagenesis. A Late Tertiary age is assigned to the shell rich limestone unit.

Keywords

Depositional And Diagenetic Environments, Petrography, Stable Isotopes, Shallow Core, Tuticorin Coast, Tamil Nadu.

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J. Madhavaraju ¹, S. M. Hussain ², M. Guruvappan ², S. Ramaswamy ², S. P. Mohan ²

Affiliations
1 Estacion Regional del Noroeste, Institute de Geologia, Universidad Nacional Autonoma de Mexrco, Hermosillo, Sonora - 83000, MX
2 Department of Geology, School of Earth and Atmospheric Sciences, University of Madras, Guindy Campus, Chennai - 600 025, IN

Abstract

The lower Niriyur Formation of Cauvery Basin is well exposed in the Periyakurichi area. The lower Niriyur Formation exhibits three carbonate petrographic types viz wackestone, packstone and boundstone whereas clastic rocks are represented by arenite and wacke types. The clastic rocks of Niriyur Formation exhibit microgranular calcite cement and fossils namely algae, bryozoa and molluses which suggest that these sediments were deposited under shallow marine environment. The carbonate rocks of Niriyur Formation contain the rich fossil assemblages composing algae, forarmnifera, ostracodes and mollusks. An attempt has been made to study the carapace-valve ratio of ostracod fauna which suggests the slow rate of sedimentation in the basin. The occurrence of Sporolithon-Rich flora together with forarmnifera has been found to be characteristic of depth range 20-40 m. The outcrop sequence stratigraphic study of the lower Niriyur Formation shows two sequence boundaries, Transgressive Systems Tract (eight shallowing upward parasequences), Maximum Flooding Surface and Highstand Systems Tract. The lower Niriyur Formation of Ariyalur area is represented by mixed clastic and carbonate rocks showing shallowing upward metre scale parasequences, which represent the subtidal cycles.

Keywords

Petrography, Sequence Stratigraphy, Parasequences, Depositional Environments, Niriyur Formation, Cauvery Basin, Tamil Nadu.

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J. S. Armstrong-Altrin ¹, J. Madhavaraju ², S. Ramasamy ², N. Gladwin Gnana Asir ²

Affiliations
1 Centro de Investigaciones en Clencias de la Tierra, Universidad Autonoma del Estado de Hidalgo, Ciudad Universitaria, Carretera Pachuca-Tulancingo km 4 5, Pachuca, Hidalgo- 42184, MX
2 Department of Geology, School of Earth and Atmospheric Sciences, University of Madras, Guindy Campus, Chennai - 600 025, Tamil Nadu, IN

Abstract

Quartz grains from Kudankulam Formation were studied using Scanning Electron Microscope(SEM), which brought out eighteen microtextures. The quartz grams of Kudankulam Formation show different types of conchoidal fracture, arcuate steps, V-shaped patterns, pits and sub angular to Sub-Rounded outline. The presence of conchoidal fracture and arcuate steps suggest that these quartz grains were derived from the nearby crystalline source. The microtextures such as V-shaped patterns, pits, straight and curved scratches are characteristic of marine environment.

Keywords

Quartz Grains, Microtextures, Kudankulam Formation, Provenance, Depositional History, Tirunelveli District, Tamil Nadu.

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J. Madhavaraju ¹, S. Ramasamy ¹, S. P. Mohan ¹, S. M. Hussain ¹, N. Gladwin Gnana Asir ¹, V. Stephen Pitchaimani ¹

Affiliations
1 Department of Geology, School of Earth and Atmospheric Sciences, University of Madras, Guindy Campus, Chennai- 600 025, IN

Abstract

Petrography, fluid inclusions and surface texture studies have been carried out on the Nimar Sandstone, which have provided fruittful results on pravenance and depositional environment The detrital omposition of sandstones plotted in the Q-F-L diagram suggests cratonic orrgin The modal percentages of different types of quartz plotted in the diamond diagram Indicate that these sediments were derived from the low-grade metamorphic rocks Quartz grains show randomly distributed primary inclusions, small trails of pseudosecondary inclusions and needle-shaped solid phases also support that the source rocks are mainly low-grade metamorphc rocks The surface textures on quartz grains reveal the presence of twenty-two distinct surface textures Based on their origin, these textures are grouped into three types viz I) thirteen features that show mechanical origin, II) five features that exhibit mechanical and/or chemical origin and III) four features that reveal chemical (precipitational)origin The quartz grans exhibit conchoidal fractures, arcuate steps, and fractured plates/planes, which resulted during the liberation of these grains from the crystalline formations They also exhibipt petransportational features such as pedological overgrowths, silica globules, flower and pellicles, which are indicative of short transportation and rapid deposition of these sediments Vs, straight and curved scratches are more common on the quartz grains from the upper Nimar Sandstone (whtch are characteristic features of marine environment), whereas the lower frequency of these features on the quartz grains from the lower Nimar Sandstone suggest fluvia depositional environments.

Keywords

Petrography, Quartz grains, Fluid inclusion, Surface textures, Nimar Sandstone, Provenance, Depositional environment, Bagh Beds, Madhya Pradesh.

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J. Madhavaraju ¹, H. J. Hansen ², S. Ramasamy ¹, S. P. Mohan ¹

Affiliations
1 Department of Geology, School of Earth and Atmospheric sciences, University of Madras. Gundy Campus, Chennai 600025, IN
2 Geological lnstitute, University of Copenhagen, Oster Volgade 10, Copenhagen, DK

Abstract

The present study reports the magnetic susceptibility study of Late Maastrichtian sediments (Kallamedu Formation) of Anyalur Group The Nimyur section exhibits two types of susceptIbility pattern Ie C-zero and C4 The susceptibility pattern of this sectIon fits well with the patterns observed In the mterval of Upper Cretaceous part of the reversed interval (29R) The K/T boundary has been fixed above the C-zero peak 10 most of the studied sections around the world We suggest that the K/T boundary should be placed above the Nimyur section, based on the characteristicc magnetic susceptibility pattern.

Keywords

Magnetic susceptibility, Late Maastrichtian, Kallamedu Formation, Anyalur Group, Tamil Nadu.

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J. Madhavaraju ¹, S. Ramasamy ¹

Affiliations
1 Department of Geology, School of Earth and Atmospheric Sciences, University of Madras, Guindy Campus, Chennai 600 025, IN

Abstract

Petrographic and geochemical studies of the Late Maastrichtian-Early Palaeocene sediments of Kallamedu and Niniyur Formations of Tiruchirapalli have brought out significant results on palaeoweathering and source area characteristics. In the bivariate plot of SiO₂ vs Al₂0₃+K₂0+Na₂0₃ all the clastic samples fall in the arid field indicating that the arid climatic condition prevailed in the source region during the deposition of these sediments. In the Al₂0₃ vs Na₂0 plot, the clastic samples fall between low grade Archaean shale and post-Archaean shale suggesting that the detrital components have been derived from low to moderately weathered terrain. The Chemical Index or Alteration of clastic sediments range from 40 to 69 with lower values for sandstones (40 to 57) than for silty shale and shale (61 to 69) and this indicates that the source rocks have undergone low to moderate chemical weathering. In QFL diagram, most of the sandstones fall in the field of cratonic interior basin which indicate that these sediments were deposited in the stable craton. SiO₂/Al₂0₃ ratios are high observed for sandstone, silty shale and shale, with a range starting from 3.15 to 8.75. The higher ratios of SiO₂/Al₂O₃ in clastic sediments indicate a largely felsic rock provenance. Major element data indicate an overall taphrogeosynclinal continental rift-related depositional basin.

Keywords

Petrography, Geochemistry, Cretaceous Sediments, Palaeoweathering, Provenance, Tiruchirapalli, Tamil Nadu.

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J. Madhavaraju ¹, S. Ramasamy ¹

Affiliations
1 Sedimentology Lab, Department of Geology, School of Earth and Atmospheric Sciences University of Madras, Guindy Campus, Chennai 600 025, IN

Abstract

Illite and smectite are the major clay minerals, whereas kaolinite and chlorite are present in small amounts in the sedimentary rocks of Ariyalur Group. The samples belonging to Ariyalur Group exhibit LREE enriched and flat HREE patterns. These samples show high ratios of CLREEIZHREE (7.65 to 19.42) which indicate that these sediments were derived from the felsic source rocks. The persistence of uniform REE patterns for the clastic samples of four formations of Ariyalur Group distinctly implies a hoinogenous nature of the source rocks. The Sillakkudi and Kallankurichchi Formations (Campanian - early Maastrichtian) exhibit high content of illite which indicate that the sediments were derived from pre-existing rocks (granites and gneiss), subjected to physical weathering in a tempcrate climate. A sudden change in illite content was noticed in Ottakkovil Formation, which probably points out a change of climate from cold to warm during middle Maastrichtian. The abundance of pedogenic smectite in the Kallamedu Formation suggests warm climate with drylwet cycles.

Keywords

Clay Minerals, REE, Ariyalur Group, Campanian, Maastrichtian, Paleoclimate.

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John S. Armstrong-Altrin ¹, J. Madhavaraju ², Alcides N. Sial ³, Juan J. Kasper-Zubillaga ¹, R. Nagarajan ⁴, K. Flores-Castro ⁵, Janet Luna Rodriguez ⁵

Affiliations
1 Instituto de Ciencias del Mar y Limnologia, Unidad de Geologia Marina y Ambiental, Universidad Nacional Autonoma de Mexico, Circuito Exterior s/n, 04510, Mexico D.F., MX
2 Estacion Regional del Noroeste, Instituto de Geologia, Universidad Nacional Autonoma de Mexico, Hermosillo 83000, Sonora, MX
3 Nucleo de Estudos Geoquimicos e Laboratorio de Isotopos Estaveis (NEG - LABISE), Departmento de Geologia, Universidade Federal de Pernambuco, Caixa Posta 7852, 50670-000 Recife, BR
4 Department of Applied Geology, School of Engineering and Science, Curtin University of Technology, CDT 250, 98009, Miri, Sarawak, MY
5 Universidad Autonoma del Estado de Hidalgo, Centro de Investigaciones en Ciencias de la Tierra, Ciudad Universitaria, Carretera Pachuca-Tulancingo Km. 4.5, 42184 Pachuca, Hidalgo,, MX

Abstract

Petrography and stable isotopes (carbon and oxygen) geochemistry of limestones from the El Abra Formation, Actopan, were studied to identify their digenetic environments. The major petrographic types identified are mudstone, wackestone, grainstone, and boundstone. Most of the studied samples show positive δ¹³C values, except two samples (2 and 28), which are slightly negative values (-0.27‰ and -0.02‰). The organic remains identified in foraminiferal wackestone type can be responsible for the negative δ¹³C values. The δ¹⁸O values range from -12.41‰ to -4.02‰ and indicate meteoric diagenesis.

Keywords

Carbonate Rocks, Carbon and Oxygen Isotopes, Diagenesis, Hidalgo State, Mexico.

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J. Madhavaraju ¹, S. Ramasamy ¹, S. P. Mohan ¹, N. Gladwin Gnana Asir ¹

Affiliations
1 Department of Geology, School of Earth and Atmospheric Sciences, University of Madras, Guindy Campus, Chennai 600 025, IN

Abstract

An ooid-rich limestone band of Sillakkudi Formation is encountered in a well section near Ariyalur. The ooids are believed to be deposited in a marine regime. They contain berthierine as the major mineral and haematite, siderite and quartz as minor minerals. They exhibit alternate rings of berthierine and haematite which shows that these minerals were developed under changing physico-chemical conditions. In the present paper, the petrographical characters, mineralogy, origin and depositional environment of the ooids are discussed.

Keywords

Ooids, Berthierine, Sillakkudi Formation, Depositional Environment, Ariyalur, Tamil Nadu.

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