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I. V. Chernyshev ¹, Yu. G. Safonov ¹, B. P. Radhakrishna ², B. Krishna Rao ³, V. N. Vasudev ², M. Deb ⁴

Affiliations
1 Institute of Geology of Ore Deposits (IGEM) Academy of Sciences, 35, Staromonetnii Street, Moscow, USSR, RU
2 Chitradurga Copper Co., IN
3 Mineralogical Inst., University of Mysore, Manasa Gangotri, Mysore 6, IN
4 Dept. of Geology, University of Delhi, Delhi 7, IN

Abstract

The isotope composition of leads from ore deposits in general reflects the age of ore mineralisation and its genetical features. Two examples have been given to illustrate a direct connection of ore lead isotope composition with the source ore. Calculations of the model age from lead isotope data form the basis for genetic reconstructions of Precambrian deposits. Radical improvement in the accuracy of mass spectrometric isotope lead analysis has made possible the employment of two-stage and in some cases more complicated models for genetic reconstructions. The Penehanga Bay lead-zinc deposit and gold-silver deposits of South Dakota have been studied using high accuracy mass spectrometer. Both the deposits show that ore formation took place one to two billion years after craton formation, and lead present in ores originated at least from two different Sources.

Keeping this background of experience, fifteen galena samples from five sulphide and gold-sulphide deposits of the Indian Shield have been selected and determination of lead isotope composition has been carried out by the Soviet authors in the USSR using recently developed M.I.1320 Mass Spectrometer. The isotopic ratios of galena from Ingaldhal copper deposit are the most primitive among the analysed ores of the Indian Shield. The results of lead isotopic determination have been interpreted in terms of the general theory of 'plumbotectonics '.

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Yu. G. Safonov ¹, B. P. Radhakrishna ², B. Krishna Rao ³, V. N. Vasudev ⁴, K. Krishnam Raju ⁵, L. P. Nosik ¹, Y. N. Pashkov ¹

Affiliations
1 Institute of Geology of ore deposits (IGEM), Academy of Sciences, 35, Staromonetnii Street, Moscow, RU
2 Geological Society of India, Bangalore 560053, IN
3 Department of Geology, University of Mysore, Manasagangotri, Mysore 570005, IN
4 Department of Mines & Geology, Bangalore 560001, IN
5 Hutti Gold Mines, Raichur District, IN

Abstract

No Abstract.

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B. Krishna Rao ¹, R. Srinivasan ², B. L. Ramachandra ³, B. L. Sreenivas ⁴

Affiliations
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

Abstract

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.

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Yu. G. Safonov ¹, A. D. Genkin ¹, V. N. Vasudev ², B. Krishna Rao ³, G. V. Anantha Iyer ⁴

Affiliations
1 Institute of Geology of Ore Deposits, Academy of Science USSR, Moscow, RU
2 Department of Mines of Geology, Bangalore 560001, IN
3 Department of Geology, University of Mysore, Mysore 570005, IN
4 Indian Institute of Science, Bangalore 560012, IN

Abstract

Twenty-five ore minerals have been identified from a study of ore-bearing samples from different reefs of the Kolar Goldfields. The mineral association includes fifteen minerals being reported for the first time: altaite, hessite hedleyite, tzumoite, volynskyite gudmundite, ullmannite, brethauptite, tetrahedrite, hawleyite, cotunite, electrum and native bismuth. Besides, two new minerals, as yet unnamed, have been determined through electronprobe - Pb₃Te₉Cl₄S₂ and PbTeCI₂ They occur along with cotunite (PbCI₂) and altaite.

The study of time relations of different ore and vein mineral assemblages in the Kolar gold-quartz reefs has revealed six stages of mineralization: 1) Early quartz, 2) quartz-feldspar (Pegmatite), 3) scheelite, 4) early sulphides with gold, 5) sulphide-gold-tellurides (with quartz) and 6) quartz-carbonate. Fluid inclusions indicate that the mineral association of quartz-feldspar stage has developed under high TP-conditions of 250-300°C and 1.8 and 3.5 kb. Isotope composition of sulphur in the sulphides indicate the juvenile nature of sulphur. Available data suggest that the quartz of first stage is of metasomatic origin, derived possibly from host amphibolites; gold-sulphide and gold-telluride mineralization took place through hydrothermal processes.

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B. M. Ravindra ¹, B. Krishna Rao ²

Affiliations
1 Geology Division, Tungabhadra Project (CADA), Munirabad 583233, IN
2 Department of Geology, University of Mysore, Mysore 570006, IN

Abstract

A set of longitudinal and transverse faults have been recognised in the coastal tract of Dakshina Kannada district. The coastal faulting and the uplift of Western Ghats are attributed to sea-floor spreading centred on the Mid-Indian Ridge in the Arabian sea. St. Mary dacite eruption during Late Cretaceous must have heralded sea floor spreading in this part of the West Coast. Variations in the coastline and discrepencies in lithology of coastal Dakshina Kannada are explained by lateral movements along transverse faults. The unusual coast-parallel bends of west flowing rivers appear to be guided by longitudinal coastal faults.

Severe sea erosion in Dakshina Kannada was initiated by the increase of pore water pressure in the coast-parallel river bends and blind tributaries, resulting from massive fluvial discharge during monsoon period. The storm waves may have reactivated preexisting longitudinal faults and triggered slumping of the foreshore sea bed in preferential areas of pore water pressure accumulation and with this, destructive sea erosion commenced and it continued till the stumped area in the foreshore bed was filled up by sands brought back by backwash currents.

It is suggested that severe sea erosion in Dakshina Kannada can be controlled effectively by devising suitable canals to release the surplus stream discharge from the coast-parallel river segments and associated blind streams.

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B. Krishna Rao ¹, P. N. Satish ¹, M. S. Sethumadhav ¹

Affiliations
1 Department of Geology, University of Mysore, Manasa Gangolri, Mysore 570006, IN

Abstract

Bauxite-bearing laterite of Boknur-Navge plateau, Belgaum district, Karnataka, exhibits textural, mineralogical and geochemical features of both syngenetic and epigenetic origin. While the syngenetic features of the lateritic residuum developed during a major episode of residual weatheringof'the source rock (Deccan basalt), the epigenetic features originated during an episode of secondary alteration of the pre-existing lateritic material.

Residual weathering of basalt took place in three stages and culminated in the formation of a well-differentiated lateritic residuum consisting of vermicular laterite and massive (textureless and pisolitic) bauxite. Lateritic weathering, under the activity of slightly acidic meteoric waters, involved leaching of ∼90% SiO₂, ∼60% Fe₂O₃ and almost all the K, Na, Ca and Mg from the weathered zone leading to the relative enrichment of Al. Part of the dissolved Si, Fe and AI of the circulating waters were subjected to local migration and reprecipitation, resulting in the segregation of AI-rich (bauxite) and Fe-Si-rich (laterite) units within the laterite profile.

Secondary products derived from the alteration of the bauxite and laterite show zonat variation in their mode of occurrence, textures, mineralogy and chemical composition. During the secondary alteration, the bauxite and laterite of the ∼10 m thick bauxite-bearing laterite zone were subjected to 1) silication and ferrification at the upper horizon, 2) silication at the intermediate horizon, and 3) minordesilication at the lower horizon. Among the three types of alterations, silication is widespread. The 'late-or post-bauxite' episode of alteration of the lateritic residuum was probably brought about by the action of highly acidic meteoric waters charged with Si.

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B. Krishna Rao ¹, Mohamed Muzamil Ahmed ¹, M. R. Janardhana ¹

Affiliations
1 Department of Geology, University of Mysore, Mysore 570006, IN

Abstract

Palynological studies on the lateritoid manganese ore revealed the presence of angiosperm, bryophyta, pteridophyta, fungi and algae. Among these Polyporina sp., Polypodiaceaesporites haardti, Palmaepollenites communis, Sapotaceoidaepollenites africanus, Pediastrum simplex var. duodenarium, Pediastrum boryanum var. undulatum and Plumbaginacipites neyvelii have been identified. They indicate that the lateritic weathering of the Precambrian manganiferous formation of the area took place during Neogene.

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B. M. Ravindra ¹, B. Krishna Rao ², V. N. Vasudev ³

Affiliations
1 Geology Wing, Tungabhadra Project (CADA), Munirabad 583233, IN
2 Geology Department, University of Mysore, Mysore 570006, IN
3 Department of Mines and Geology, Mineral Wing, Bellary 583101, IN

Abstract

Low-grade copper sulphide mineralisation around Kalyadi is localised in an early Precambrian volcanosedimentary suite, characterised by cyclic sedimentational features. The rocks have been intruded by ultramafics, granite and dolerite. The supracrustals have been subjected to three phases of deformation and low-grade metamorphism.

The Fe-Cu sulphide mineralisation is stratiform and stratabound, represented by pyrite. chalcopyrite and pyrrhotite. The salient features of tbe mineralisation suggest that the sulphide ore material derived from volcanic exhalatives was deposited along with their volcanosedimentary host rocks syngenetically about 3.0 b.y. ago. The mineralisation is essentially a sulphide facies of iron-formation. Banded ferruginous quartzite also exists in the area, suggesting consanguineous sulphide-oxide facies relationship. The ore has been deformed and metamorphosed along with the host rocks resulting in mobilisation and moderate enrichment.

Keywords

Economic Geology, Metals, Ore Petrology, Copper, Hassan District, Karnataka.

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B. Chadwick ¹, V. N. Vasudev ², B. Krishna Rao ³, G. V. Hegde ²

Affiliations
1 Earth Resources Centre, University, Exeter EX44QE,, GB
2 Department of Mines and Geology, Government of Karnataka, 16/3-5 S.P. Complex, Lalbagh Road, Bangalore 560027, IN
3 Department of Geology, University of Mysore, Manasa Gangotri, Mysore 576 006, IN

Abstract

The Dharwar sedimentary and volcanic rocks adjacent to their basement granodiorites and gneisses in the Honnali dome can be interpreted in terms of three principal lithostratigraphic units. Each unit represents a distinct stage of basin development. The lowest unit is formed by the mainly shallow marine metabasite-orthoquartzite association of the Bababudan Group. It marks an early extensional phase of basin development. The group in the Honnali area has been subdivided into the Kudrekonda and Kalva Rangan Durga Formations. The second unit comprises mainly shallow marine sedimentary rocks, including polymict conglomerates and limestones, with intercalations of basic to acid volcanic rocks. The lithological association indicates unstable depositional and volcanic conditions with variable uplift and subsidence during the second stage of basin development. The unit is equivalent to the lower part of the Chitradurga Group and it has heen subdivided into the Musinhal, Adrihalli, Aleshpur, Medur and Daginkatte Formations. The acid volcanic rocks forming the Daginkatte Formation were formerly regarded as rhyolitic flows, but they are reinterpreted as ash flow deposits on the grounds of their textures. The third unit corresponds to the upper part of the Chitradurga Group. It begins with the thin, but persistent Basavapatna Formation of banded ferruginous cherts and interbedded carbonaceous phyllites. This formation is overlain by the re-defined Ranibennur Formation of greywackes and local volcanic intercalations. Whilst a marine setting with initial widespread quiescent conditions is indicated by the third unit, its significance is uncertain because of the lack of data from the large, but poorly exposed tract of greywackes.

The Dharwar rocks are dominated by ductile structures in the form of south or southwesterly verging inclined folds with superimposed, steep north-trending folds. In contrast, the basement rocks in the Honnali dome deformed cataclastically on myriad fractures and retrograde shear zones. The dome has a faulted southern boundary, whilst a steepened unconfonnity forms the remaining parts of the boundary. The contrasting structures in the cover and the basement may be modelled in terms of crustal shortening propagating from the north ornortheast on listric faults dipping northeast through the basement into a deep detachment. Later strike-slip displacements on steep NS faults and shear zones modified the south-verging structures. Alternatively, the structure may be interpreted in terms of jostling of basement blocks within a zone of transpression related to sub-horizontal displacements on NS faults and shear zones.

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B. Krishna Rao ¹, M. Hanuma Prasad ¹, V. N. Vasudev ², M. S. Sethumadhav ¹

Affiliations
1 Department of Geology, University of Mysore, Manasagangotri, Mysore-570006, IN
2 Department of Mines and Geology, 16, S.P.Complex, Lalbagh Raod, Bangalore-560027, IN

Abstract

Magnesite mineralization in the Copper Mountain areaofthe Sandurschist belt occurs scattered in a 5 km long and 50 to 200 m wide grunerite schist unit of Late Archaean age. Magnesite occurs mostly as less than a cm to about 50 cm thick parallel to subparallel veins. The veins are confined to gently dipping joints and tensional fractures transecting the steeply dipping bedding and schistosity of the host rock. Magnesite is cryptocrystalline and is associated with minor amounts of dolomite/magnesian calcite, calcite, cryptocrystalline silica and iron oxyhydroxides. Magnesite veins are essentially of cavity filling origin. Field setting, rock and mineral chemistry and stable isotope data indicate that magnesite was precipitated at ambienttemperatures from descending meteoric waters enriched in biogenic and atmospheric CO₂ and Mg²⁺, the latter derived from the upper weathered portion of the host grunerite schist.

Keywords

Magnesite, Economic Geology, Weathering, Sandur Schist Belt, Karnataka.

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B. Krishna Rao ¹, M. Hanuma Prasad ¹

Affiliations
1 Department of Geology, University of Mysore, Mysore 570006, IN

Abstract

Chemical composition of the phyllites of the Copper Mountain region of the late Archaean Sandur Schist belt in the eastern block of the Dharwar craton indicates that the fine-grained clastic sediments from which they were formed, were derived from a provenance comprising -60% felsic, - 30% mafic and 10% ultramafic rocks. High Zr/Nb and Zr/Y ratios and lack of strong -ve Eu anomalies suggest that the felsic component of the provenance was dominantly made up of tonalites-trondhjemites; granites and granodiorites were very subordinate constituents. The sediments appear to have accumulated in a continental island are environment. Rarity of granitic constituents in the pre-Dharwar provenance of Sandur basin contrasts with the abundance of such constituents in the provenance for the fine-grained clastic sediments of basins in the western block of the Dharwar craton. The continental crust of the eastern block was apparently less evolved during the pre-Dharwar time as compared to that in the western block of the Dharwar craton.

Keywords

Geochemistry, Phyllites, Copper Mountain, Sandur Schist Belt, Karnataka.

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A. P. Nutman ¹, Brian Chadwick ², B. Krishna Rao ³, V. N. Vasudev ⁴

Affiliations
1 Research School of Earth Sciences, Australian National University, A.C.T. 0200, AU
2 Earth Resources Centre, University of Exeter, Exeter EX4 4QE, GB
3 Department of Geology, University of Mysore, Mysore - 570 006, IN
4 120/45(A), III Block, Thyagarajanagar, Bangalore - 560 028, IN

Abstract

SHRIMP U/Pb dating of zircon grains from a schistose acid volcanic rock from the Daginkatte Formation in the Chitradurga Group of the Late Archaean Dhwar Supergroup in western Karnataka has yielded a precise concordant age of 2614 ± 8 Ma which indicates the time of melt crystallisation. In contrast, zircons from similar schistose acid volcanic rocks in the Vibhuti Gudda Formation of the Sandur Group in the Sandur schist belt of eastern Karnataka yielded less precise concordia intercept ages of 2658±14 and 2691±18 Ma.

Zircons from high-strain grey gneisses which appear to be the oldest recognisable component of the Late Archaean granite complex adjacent to the Sandur schist belt have an imprecise age of 2719 ± 40 Ma. Zircons from the youngest recognisable granite adjacent to the belt have also yielded an imprecise, but younger, age of 2570 ± 62 Ma. The ages show that granite emplacement and deformation adjacent to the Sandur schist belt took pIace in a period of c.150 Ma.

The imprecise ages of zircon in the acid volcanic rocks in the Sandur Group and the adjacent granites are related to Neoproterozoic loss of lead which may have been an effect of either weathering or a regional thermal event. We favour the latter in the light of the record of Pan-African thermal effects in the east and south of southern Peninsular India.

Keywords

Geochronology, Zircon, Acid Volcanics, Sandur Schist Belt, Karnataka.

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B. Krishna Rao ¹

Affiliations
1 Geology Department, Andhra University, Visakhapatnam - 530 003, IN

Abstract

No Abstract.

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M. Hanuma Prasad ¹, B. Krishna Rao ², V. N. Vasudev ¹, B. Basavalingu ¹

Affiliations
1 Department of studies in Geology, University of Mysore, Mysore 570 006, IN
2 Department of Mines and Geology, 16, S.P. Complex, Lalbagh Road, Bangalore 570 027, IN

Abstract

Compositions of co-existing mineral pairs, viz., (a) cordierite- gedrite- garnet- biotite, (b) staurolite-biotite-garnet-muscovite-chlorite and (c) andalusite-staurolite-biotite-gamet in metapelites, and (d) amphibole-plagioclase pair in metabasalts of the Sandur schist belt in the eastern block of the Dharwar craton, Southern India, yield metamorphic temperatures and pressures in the range of 550°-600° C and 4-5.2 kbar, respectively. Textural relationships of the minerals in the above mineral assemblages suggest the development of cordierite, gedrite, garnet, staurolite and biotite during the main-fabric forming event (regional metamorphism). Increase in the grade of metamorphism from greenschist to amphibolite facies associated with the main deformational event is observed from the central to the peripheral portions of the belt; this can be attributed to the steep thermal gradient produced by the syntectonic granitoids. Andalusite post-dates all the other metamorphic minerals and its development outlasts the main deformational episode in the belt. Andalu∼ite is a product of thermal metamorphism, superimposed on regional metamorphism and its growth coincides with the upliftment of the terrain during the emplacement of Iate- to post-kinematic granitoids, which, under comparatively low pressure regime (∼3.75 kbar), maintained earlier peak metamorphic temperatures.

Keywords

Metamorphic Petrology, Sandur Schist Belt, Kamataka.

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M. Hanuma Prasad ¹, B. Krishna Rao ¹, V. N. Vasudev ², R. Srinivasan ³, V. Balaram ³

Affiliations
1 Department of Geology, University of Mysore, Manasagangotri, Mysore - 570 006, IN
2 Mineral Resources Consultant, 120/45(A), 3^rdBlock, TR Nagar, Bangalore - 560 028, IN
3 National Geophysical Research Institute, Uppal Road, Hyderabad - 500 007, IN

Abstract

In the late Archaean Sandur supracrustal belt of the Dharwar craton, Southem India, bimodal (mafic-felsic) volcanic rocks are encountered in its eastern region (Copper Mountain region). The mafic volcanic rocks are represented by Al-depleted picritic basalt and tholeliitic basalt. Pieritic basalt has a HREE - depleted pattern. Tholeliitic basalt exhibits two types of REE patterns; (a) slightly depleted - to flat - LREE and unfractionated HREE patterns, and (b) LREE - enriched and HREEdepleted patterns. The felsic volcanic rocks are Na-Rhyolites, which show calc-alkaline affinity and LREE - enriched and HREE-depleted chondrite-normalised patterns. Geochemical signatures show that the picritic basalt owes its origin to melting of a mantle diapir at depths around 100 km. The LREE - depleted tholeiites are not genetically related to the picritic basalt. They were derived through high degree partial melting of a depleted shallow mantle source. The internal variations observed in the LREE - depleted tholeiitic suite are due to derivation of magma through different degrees of melting of the same mantle source. REE-based petrogenetic modelling shows that the LREE - depleted and LREE - enriched tholeiites are not related to a common parent magma. The LREE - enriched tholeiites were generated from a mantle source, which has been metasomatized by subduction related melt/fluid phase. REE chemistry shows that the mafic and felsic volcanic rocks, though spatially and temporally associated, are not genetically related. The HREE depleted rhyolites were derived by partial melting of a garnet - amphibole bearing source, possibly a subducting oceanic crust. Feild, geochemical and petrogenetic aspects suggest that the magmatic rocks of the study area evolved in an active plate margin environment.

Keywords

Geochemistry, Meauics, Late Archaean Sandur Belt, Kamataka.

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B. Krishna Rao ¹, M. S. Sethumadhav ¹, M. Hanuma Prasad ², T. D. Mahabaleshwar ¹, Ashok V. Rao ¹, H. Albert Gilg ³

Affiliations
1 Department of studies in Geology, University of Mysore, Manasagangotri, Mysore - 570 006, IN
2 Geological survey of India, Sanjivani Nagar, Garha Road, Jabalpur - 482 003, IN
3 Institute for Mineralogy and Geochemistry, Technical University of Munich, Lichtenberg str, D-85747, Garching, Munich, DE

Abstract

Vein-type magnesite deposit of Doddakanya area is situated in the southern part of the Archaean Dharwar craton. Magnesite is confined to a c.3.3 Ga old ultramafic body which constitutes a tectonically dismembered part of a layered ultramafic-mafic complex emplaced into supracrustal rocks of the Sargur Group. The magnesite-bearing ultramafic body is composed of dunite with minor harzburgite and exhibits varying degrees of serpentinization and weathering. About 50 vol.% of the ultramafic body is serpentinized and the intensity of serpentinization decreases with depth. The serpentine minerals are represented essentially by lizardite/chrysotile exhibiting pseudomorphic mesh-texture. Serpentinization of the ultramafic body took place within 6 km of the Earth's surface at low temperatures (<200°C) and essentially involved volume expansion (isochemical) process. During weathering, the relict olivine of the serpentinized ultramafic body was pseudomorphously replaced by a mixture of amorphous material (with variable amounts of Fe, Mg, Si and volatiles) and minor ferric oxyhydroxides and secondary silica. The Mg mobilized during weathering participated in the formation of magnesite in tensional fractures developed during the late- to post-serpentinization event. Oxygen isotope data  (δ¹⁸O = av. 30.6‰ SMOW) indicate the precipitation of magnesite at ambient temperatures and carbon isotope values (δ¹³C = av. -2.6‰ PDB) suggest the derivation of carbon from a biogenic soil source dominated by C4 plants. The latter constrains the timing of the magnesite formation to a period not older than 8 - 7 Ma.

Keywords

Economic Geology, Archaean Ultramafic Rocks, Vein-Type Magnesite, Serpentinization, C and O Isotopes, Supergene Origin, Doddakanya, Karnataka.

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M. Hanuma Prasad ¹, Asfar Hakim ¹, B. Krishna Rao ²

Affiliations
1 GSI Colony, Sanjivani Nagar, Jabalpur - 482 003, IN
2 Department of Geology, University of Mysore, Mysore - 570 006, IN

Abstract

The Bundelkhand Granitic Complex of central India contains inclusions of Archaean volcanic and sedimentary rocks and orthogneisses, some of which are 15 km by 6 km in size, Earlier workers considered that these inclusions belong to two distinct lithostratigraphic formations separated in time by a migmatization event. Our new data suggest that the migmatization event post-dated all of the volcanic and sedimentary rocks and hence the two-fold stratigraphic subdivision is not viable. Further, intrusion of orthogneisses resulted in an increase in grade of metamorphism in some volcanic and sedimentary rocks specifically near the contact.

Keywords

Structural Geology, Orthogneisses, Volcanic and Sedimentary Rocks, Bundelkhand Granitic Complex, Madhya Pradesh.

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B. Krishna Rao ¹, R. S. Kurothe ¹, P. K. Mishra ², Gopal Kumar ¹, V. C. Pande ¹

Affiliations
1 Central Soil and Water Conservation Research and Training Institute, Research Centre, Vasad 388 306, IN
2 Central Soil and Water Conservation Research and Training Institute, 218 Kaulagarh Road, Dehradun 248 195, IN

Abstract

A study was carried out to determine the effect of cli-mate change on design rainfall and its effect on design and costing of soil and water conservation structures in watersheds. For this study, the micro watershed located at Central Soil and Water Conservation Research and Training Institute, Research Centre, Research farm, Vasad was selected and rainfall data from 1957 to 2012 was used. The analysis showed that as a result of climate change, there is significant in-crease in number of extremely heavy rainfall days as well as rainfall amount. The design rainfall of various soil and water conservation structures has increased by 11%, 30% and 38% for design of staggered con-tour trenches, contour bunds and check dams respec-tively. The cost of construction of staggered contour trenches, contour bunds and check dams in water-sheds has increased by 26%, 28% and 12% respec-tively. This study reveals that, there is a need to account for design and costing of soil and water con-servation structures in the light of the climate change and a relook into the watershed programmes of the central Gujarat region of India.

Keywords

Climate Change, Design And Costing, Soil and Water Conservation Structures, Watersheds.

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R. Srinivasan ¹, B. L. Sreenivas ², B. Krishna Rao ²

Affiliations
1 Geomysore Services, 12 Palace Road, Bangalore-560 052, IN
2 Geomysore Services, 12 Palace Road, Bangalore-560 052., IN

Abstract

Peninsular Gneiss' is a product of syntectonic remobilization of some sialic basement (Fundamental gneiss?) with reference to Dharwar folding. The preservation or obliteration of the basement relation with respect to Dharwars is a function of varying degrees of remobilization characteristic of low pressure and high pressure metamorphic belt regions of Karnataka. By remobilization the basement highs within the schist belts were transformed to mantled gneiss domes, and tonalites were made over to granodiorites and adamellites. With a common source of heat, accompanying the remobilization, retrogression of high grade metamorphic rocks of older' Sargur Supergroup' and prograde metamorphism of volcanics and sediments of 'Dharwar Supergroup' were accomplished.

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