A B C D E F G H I J K L M N O P Q R S T U V W X Y Z All
Ramasamy, S.
- Dropstones in Talchir Sediments of Palar Basin, Tamil Nadu - Implications on Depositional Conditions and Paleoclimate
Authors
1 Sedimentology Lab, Department of Geology, School of Earth and Atmospheric Sciences, University of Madras, Guindy Campus, Chennai 600 025, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 56, No 1 (2000), Pagination: 47-52Abstract
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.- Microtextures on Quartz Grains of Campanian-Maastrichtian Sediments of Ariyalur Group of Tiruchirapalli Cretaceous, Tamil Nadu - Implication on Depositional Environments
Authors
1 Sedimentology Lab, Department of Geology, School of Earth and Atmospheric Sciences, University of Madras, Guindy Campus, Chennai - 600 025, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 54, No 6 (1999), Pagination: 647-658Abstract
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.- Depositional Environment of Cuddalore Sandstone Formation, Tamil Nadu
Authors
1 Department of Geology, University of Madras, A.C. College Campus, Madras 600 025, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 51, No 6 (1998), Pagination: 803-812Abstract
Cuddalore Sandstone (Mio-Pliocene) of Neyveli and Ariyalur areas has been studied to infer the depositional environment. Granulometrically, poorly to moderately sorted and fine to very finely skewed sandstones are petrographically identified as feldsarenite and litharenite. Source area for the Neyveli sediments included pyroxenite, amphibolite and granodiorite and the Ariyalur sediments were probably, derived from granite and monzonite. Major elemental data show the eugeosynclinal tectonic setting for Neyveli and taphrogeosynclinal setting for Ariyalur area. The overall study suggests a deltaic environment.Keywords
Sedimentology, Cuddalore Sandstone, Mio-Pliocene, Depositional Environment, Neyveli, Tamil Nadu.- Geology, Petrography and Systematic Stratigraphy of Pre-Ariyalur Sequence in Tiruchirapaui District, Tamil Nadu, India
Authors
1 Department of Geology, University of Madras, Madras 600025, IN
2 Department of Earth Sciences, Indian Institute of Technology, Bombay 400076, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 37, No 6 (1991), Pagination: 577-594Abstract
A new litho unit-Terani Formation is proposed. The lower part of the Uttatur Formation is found to be homotaxially equivalent to the Dalmiapuram Formation. A new geological map based on these units is presented.Keywords
Ariyalur Sequences, TiruchirapaJli Dist., Tamil Nadu, Petrography.- Rare Earth Element Geochemistry of a Sediment Core from the Lower Bengal Fan
Authors
1 Department of Geology, University of Madras, Guindy Campus, Madras - 600 025, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 50, No 4 (1997), Pagination: 399-406Abstract
The Post Archaean Australian Shale (PAAS) normalised Rare Earth Element (REE) distribution pattern of a 4m box core from the Lower Bengal Fan clearly exhibits different types of patterns according to the climatic fluctuations of Late Quaternary period. Based on the vertical profiles of REEs, ΣLight REE/ΣHeavy REE ratio, Ce^ and ΣREE the climatic boundaries were further confirmed. The influence of continental sediments with a rugher rate of sedimentation are reflected in higher concentration of ΣREE in glacial periods. The above observations suggest the Late Pleistocene - Holocene boundary at 45-50 cm depth, the Last Glacial Maximum at 50-120cm depth and Glacial (I) stage at 150-290cm depth in the core studied. Warmer periods of Interglacial stages (II) and (I) correspond to 120-150cm and 290-400cm depths.Keywords
Geochemistry, Rare Earth Elements, Quaternary, Bengal Fan.- Rare Earth Elements in Limestones of Kallankurichchi Formation of Ariyalur Group, Tiruchirapalli Cretaceous, Tamil Nadu
Authors
1 Sedimentology Lab. Department of Geology, School of Earth and Atmospheric Sciences, University of Madras, Guindy Campus, Chennai 600 025, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 54, No 3 (1999), Pagination: 291-301Abstract
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 LaN/YbN ((LaSample/LaShale)/(YbSample/YbShale)) 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.- Petrography and Geochemistry of Pre-Ariyalur Sequence in Perambalur District, Tamil Nadu-Implications on Depositional Environment and Palaeoclimate
Authors
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
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 69, No 1 (2007), Pagination: 121-132Abstract
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.- Depositional and Diagenetic Inferences of a Shallow Core near Tuticorin Coast, Tamil Nadu
Authors
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
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 70, No 6 (2007), Pagination: 1021-1032Abstract
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.- Provenance and Depositional History of Sandstones from the Upper Miocene Kudankulam Formation, Tamil Nadu
Authors
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
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 66, No 1 (2005), Pagination: 59-65Abstract
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.- Petrography and Surface Textures on Quartz Grains of Nimar Sandstone, Bagh-Begs, Madhya Pradesh - Implications for Provenance and Depositional Environment
Authors
1 Department of Geology, School of Earth and Atmospheric Sciences, University of Madras, Guindy Campus, Chennai- 600 025, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 64, No 6 (2004), Pagination: 747-762Abstract
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.- Magnetic Susceptibility Study of Late Maastrichtian Sediments of Ariyalur Group of Tiruchirapalli Cretaceous, Tamil Nadu
Authors
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
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 61, No 6 (2003), Pagination: 699-702Abstract
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.- Petrography and Major Element Geochemistry of Late Maastrichtian- Early Palaeocene Sediments of Tiruchirapalli, Tamil Nadu - Palaeoweathering and Provenance Implications
Authors
1 Department of Geology, School of Earth and Atmospheric Sciences, University of Madras, Guindy Campus, Chennai 600 025, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 59, No 2 (2002), Pagination: 133-142Abstract
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.- Stable Isotope Geochemistry and Evidence for Meteoric Diagenesis in Kudankulam Formation, Tamil Nadu
Authors
1 Sedimentology Laboratory, Department of Geology, University of Madras, Guindy Campus, Chennai - 600 025, IN
2 Institute of Geological Sciences, National Academy of Sciences of Belarus, Kuprevich Street 7, 220141 Minsk, BY
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 57, No 1 (2001), Pagination: 39-48Abstract
The results obtained from stable isotope study of Neogene carbonates of Kudankulam, Tamil Nadu show negative values for δ13C, which range from -2.6‰ to -9.7‰ PDB. The δ18O values range from -4.5‰ to -11.4‰ PDB. The depleted nature of the δ18O and δ13C values suggests the strong effect of meteoric diagenesis in the Kudankulam carbonates. Standard bivariate plots of δ18O versus δ13C for carbonate materials/rocks helped to identify their depositional and diagenetic environments. Petrographic study points out large-scale emplacement of ferroan sparry calcite cement into vugs and other leached cavities.Keywords
Limestones, Miocene, Petrography, Geochemistry, Stable Isotopes, Diagenesis, Tamil Nadu.- Clay Mineral Assemblages and Rare Earth Element Distribution in the Sediments of Ariyalur Group, Tiruchirapalli District, Tamil Nadu-Implication for Paleoclimate
Authors
1 Sedimentology Lab, Department of Geology, School of Earth and Atmospheric Sciences University of Madras, Guindy Campus, Chennai 600 025, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 58, No 1 (2001), Pagination: 69-77Abstract
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.- Inferences on Rhodoids from Neogene Carbonates of Kudankulam, Tamil Nadu
Authors
1 Sedimentology Laboratory, Department of Geology, University of Madras, Chennai - 600 025, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 52, No 3 (1998), Pagination: 341-344Abstract
Rhodoids are laminated algal nodules generally found in shallow marine environment. Algal crusts and nodules are poorly exposed between Kudankulam and Sattankulam in the coastal area near Cape Comorin. The thickness of the bed of algal limestone varies from 0.5 to 1.5 m. The occurrence of abraded rhodoids with lack of terrigenous material suggests moderate to high energy depositional condition. The present study of the rhodoids, points out that the Neogene tectonic activity has played a significant role for the development of algal limestone and rhodoids in the study area.Keywords
Palaeoenvironment, Rhodoids, Neogene Carbonates, Tamil Nadu.- Ooids in Sillakkudi Formation of Ariyalur Group of Tiruchirapalli Cretaceous, Tamil Nadu: Implications for Origin and Depositional Environment
Authors
1 Department of Geology, School of Earth and Atmospheric Sciences, University of Madras, Guindy Campus, Chennai 600 025, IN