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Sreenivas, B. L.
- Dharwar Conglomerates of Mysore - A Restudy
Authors
1 Department of Geology, Central College, Bangalore University, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 9, No 2 (1968), Pagination: 197-205Abstract
Compositional layering of pebbles has provided a positive structural criterion in distinguishing the tectogenic (autoclastic) conglomerates from the sedimentogenic ones in the Dharwars of Mysore. Making use of current bedding and graded bedding as markers of two different tectonic environments of arenite sedimentation, the stable areas of deposition in Dharwars of Shimoga, Chital drug and Bababudan schist belts are separated from the main geosynclinal regions. Stability in the depositional environment is found to be characteristic of the parageosynclinal stage; and the conglomerates deposited in stable regions are oligomictic as against the polymictic nature of the geosynclinal conglomerates.- Dharwar Stratigraphy
Authors
1 Department of Geology, Mysore University, Mysore, IN
2 Bangalore, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 13, No 1 (1972), Pagination: 75-85Abstract
Reconsideration of the stratigraphy of the Dharwars of Mysore State in the light of new data suggests that they are Paleoproterozoic and overlie Charnockites of Archean age. Classification of Dharwars based on tectonomagmatic and atmospheric evolution leads to a four fold divison. Pregeosynclinal shelf stage iS represented by two cycles of platformal sedimentation and magmatism; the earlier, under oxygen deficient conditions, on mafic platforms built by subaerial lavas, Is represented by Bababudan Series, and the latter under oxygenic conditions accompained by alkaline ultramafic intrusions gave rise to Dodguni Series. The geosynclinal Stage represented by pillow-Iava-greywacke-Iron ore deposition (third cycle of magmatism and sedimentation) constitutes the Grey trapRambennur Series. Early tectonic plagioclase granites-Champion gneisses syntectonic migmatites-Peninsular gneisses and late to post-tectonic alkali metasomatic granites Closepet granites (fourth, fifth and sixth magmatic cycles) developed during the folding and metamorphism of Dharwar geosynclinal pile. The inversion of geosyncline witnessed apogeosynclinal molasse red bed Sedimentation (fourth cycle of sedimentation) represented by G. R. Series. Paleoproterozoic epidiorites and post-Paleoproterozoic dolerites cratonised the area.- Geochemistry of Granite-Greenstone Terrain of South India
Authors
1 Geomysore Services, Bangalore
2 Geomysore Services, Bangalore, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 15, No 4 (1974), Pagination: 390-406Abstract
A critical evaluation of the available major and trace element data on rocks of the granite-greenstone belts or South India leads to the following inferences: Barrovian and Abukuma facies series of metamorphism are recognizable in the terrain. Rocks of peridotitic and basaltic komatiite affinities occur in the pre-Dharwar and early Dharwar ultramafic-mafic sequence. The bulk of the greenstones are island arc tholeiites with a strong calc-alkaline affinity. The presence of detrital pyrites in the oldest conglomerates, and the occurrence of red beds in the topmost Dharwar sequence, indicate that an oxygenic atmosphere evolved through the Dharwar times. The pre-Dharwar granitoids were probably tonalitic, and through time, alkali fractionation gave rise to the Champion gneisses, Peninsular gneisses and Closepet granites. The available data are inadequate to elucidate the fractionation pattern of the granitic crust of Peninsular India.
Pyrolite and eclogite mantle are invoked for tectonomagmatic events during the pre-Dharwar and Dharwar times, respectively. Convection, and eclogite sinkers, are proposed as alternative geodynamic models.
From the geochemical evolution, it is contended that the granite-greenstone belts of Peninsular India represent a more evolved crustal condition as compared to the Archaean granite greenstone belts of South Africa and Western Australia. Obviously, the granite-greenstone belts of all the shield areas, did not evolve simultaneously.
- Komatiite Dykes of Dodkanya, Mysore District, Karnataka State, India
Authors
1 Geomysore Services, 12, Palace Road, Bangalore 560 052, IN
2 Chitradurga Copper Co., Ali Asker Road, Bangalore 560052, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 16, No 4 (1975), Pagination: 508-512Abstract
No Abstract.- Some New Geological Features from the Landsat Imagery of Karnataka
Authors
1 Geomysore Services, 12, Palace Road, Bangalore 560052, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 18, No 11 (1977), Pagination: 589-597Abstract
A preliminary interpretation of black and white LANDSAT IMAGERY of a major part of Karnataka state on 1:1 million scale has been attempted to interpret structure, landforms, mineral and groundwater occurrence, and engineering and environmental conditions. Ground truth of the interpretations needs to be investigated.- Mode of Occurrence and Origin of Manganese Ores of Shimoga District, Karnataka
Authors
1 Mineralogical Institute, University of Mysore, Manasagangotri, Mysore 570 006, IN
2 INSA Project, Dept. of Mines and Geology, Race Course Road, Bangalore 560 001, IN
3 Mysore Minerals Ltd., 39, Mahatma Gandhi Road, Bangalore 560 001, IN
4 Geomysore Services, 12, Palace Road, Bangalore 560 052, DE
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 23, No 5 (1982), Pagination: 226-235Abstract
Four types of manganese ores are distinguished: 1. Reworked metasedimcntary ore in Precambrian banded manganese formation; 2. Sedimentary oolitic/pisolitic ore associated with claystone; 3. Cavity filling/replacement type ore in weathered Precambrian phyllitic schists and laterites; 4. Bouldery-pebbly float ore in soils and laterite. The reworked metasedimentary ore is low in silica (∼6%), high in Fe content (∼26%) and its Mn/Fe ratio varies between 0.75 and 1.2. The oolitic/pisolitic ore on the other hand is high in silica (∼14%), low in Fe ( ∼17%) and Mn/Fe ratio of 1.7 and 2.1. Supergene processes, during Tertiary-Quaternary (7) have contributed significant quantities of sedimentary oolitic/pisolitic ore and minor amount of cavity filling/replacement type ore. The surficial exposures of reworked metasedimentary and oolitic/pisolitic ores have been subjected to mechanical disintegration and detrital accumulation with repeated breaks leading to extensive development or float ore in both laterite and soil profile.- Evolution of Peninsular Gneiss Restraints, Reasons and Reflections
Authors
1 Geomysore Services, 12 Palace Road, Bangalore-560 052, IN
2 Geomysore Services, 12 Palace Road, Bangalore-560 052., IN