Dharwar super group

This presentation includes brief information about Dharwar Supergroup of Indian Stratigraphy. Dharwar is one of the major craton of India.

1. DHARWAR SUPER GROUP PresenteD by Haroon muhammed MIT- MAHE

2. INTRODUCTION Dharwar craton – one of 5 major cratons of Indian Shield Covers an area of 450,000 sqr.km Known for its greenstone/schist belts, grey gneisses, charnockites and younger granites. Dharwar craton divided in to: Western dharwar craton Eastern dharwar craton Divided by the chitradurga shear zone.

3. The craton is bounded by South – Pan African ‘ Pandyan Mobile Belt’ North – Deccan Flood Basalts East - Eastern Ghat Mobile belt West - extends westwards into offshore limit defined by cretaceous oceanic layer in Arabian sea.

4. Tectonic divisions of Indian Shield.

5. Dharwar Craton -

6. STRATIGRAPHY OF DHARWAR CRATON -

7. WESTERN DHARWAR CRATON(WDC) WDC is located in southwest India . Western Dharwar Craton (WDC) is occupied by three suites of north-south oriented metamorphic belts : oldest- surgur group, peninsular gneissic complex and youngest dharwar super group. Metamorphism is regional, effecting all parts of craton. The principle structural trend in WDC is NW – SE to north south Rocks have been deposited during 3400-2500 m.y .

8. EASTERN DHARWAR CRATON(EDC) The Craton is composed of the Dharwar Batholith , greenstone belts , intrusive volcanics , and middle Proterozoic to more recent sedimentary basins . The supracrustal belts of the EDC are smaller in size than those of the western blocks. O lder greenstone belts that are either older or equivalent to the Bababudan Group of the western block. Metabasalts from Kolar schist belt indicating that they are contemporaneous with the Chitradurga Group of the western block (WDC). The contact between WDC and EDC is separated by chitradurga shear zone. Greenstone belts are seen in kolar and ramagiri area.

9. DHARWAR SUPER GROUP The Dharwar supergroup is deposited unconformably over a sialic basement of tonalitic and granitic “Peninsular Gneiss ”. Dharwar supergroup is exposed as 2 major schist belts: 1.Bababudan- ­‐ Western Ghat - ­‐ Shimoga Schist belt. 2 . Chitradurga -­‐ Gadag Schist Belt. Younger schist belts belonging to dharwar supergroup are charecterised by metamorphism predominantly of greenstone facies . They contain abundance of clastic and quartzose sedimentary rocks -conglomerates containing clasts of underlying gneisses.

10. DHARWAR SUPER GROUP Typical rocks – arenite, shales, volcanic rocks varying from basalts to rhyolites, cherts , phyllites and carbonates. Well known examples are exposed in chitradurgah , shimoga , bababudan and kudremukh . Total thickness of these Dharwar schist belts is estimated to be 6 to 7 km . Age of the Dharwar SuperGroup -3.0-2.6 b.y .

11. BABABUDAN GROUP. The belt occupying an area of 300km long and 100km wide. Schistose rock occupy an area of 30000 sq. km, remaining 15000sq.km occupied by basement peninsular gneisses. This group is dominantly made up of Metabasalt with interbedded quartzite, capped by a prominent BIF Age is about 2700 – 2800my.

12. BABABUDAN GROUP BABABUDAN GROUP Bababudan Group of rocks are exposed mainly in Bababudan , Western Ghats, arm of Chitradurga schist belt . The bababudan group unconformbly lies over the gneissic basement. The Bababudan sediments and Volcanics suggest nearshore and subaerial to shallow marine environment respectively. The rocks of Bababudan Group are metamorphosed upto lower amphibolites facies (garnet isograd ) at the borders and green schist facies at the core portions.

13. BABABUDAN GROUP The bababudan group is sub-divided into kalsapura formation, Allembur formation, santaveri formation and Mulaingiri formation. The sequence of rocks in bababudan starts with oligomectic quartz pebble conglomerate which consist of gold. Succeeding quartzite exhibits ripple marks, indicating stable shelf conditions. The quartzites are interbedded with baslats .

14. BABABUDAN GROUP These rocks are overlain by a very thick layer of BIF’s. which is followed by schist , greywacke and Conglomerate.

15. CHITRADURGA GROUP The lower- bababudan group and upper chitradurgah group are separated b an unconformity. Commonly this belt is known as Chitradurga Schist Belt(CSB). Cover an area - 400KM long, 40km width at the centre and tepers towards 2km width towards south. The chitradurga group is sub- divided into Vanivilas , Ingaldhal and Hiriyur formation . CSB extends from gadag in the north to srirangapatanam in the south The southern part of schist belt consist of ultrmafic schist, amphibolites , silecious sedimentary rocks and marbles. The middle part of the belt consist of amphibolite, fuchsite quartzite, metabasalts , conglomerate, phyllite , iron and manganese formation.

16. CHITRADURGA GROUP

17. CHITRADURGA GROUP The northern part of the belt consist of conglomerate, phyllite , volcanics , BIF’s , Mn - formations, quartzite and chert . The varieties of volcanic rock ranges from spinifex textured komatiite, pillowed metabasalt , andesite and rhyolite. Eastern part of the belt is known as Javanahalli belt.(gneisses and amphibolites ).

18. ECONOMIC IMPORTANCE The Archean Group of rocks, of which dharwars forms a very important. These group are regarded as the most important economic mineral bearing Groups of India stratigraphy. Most of the economic minerals like those of iron, copper manganese, lead , zinc, and gold etc. have come from rocks which broadly belongs to Archean time. As regards mineralization, 1. The western block is characterized by copper, iron and manganese mineralization , whereas 2. The Eastern Block is known for gold, iron and manganese mineralization.

19. CONCLUSION Dharwar super group is exposed both in WDC mainly and EDC. Age is about 2600-3000MY . In WDC dharwar super group as divided into chitradurga and bababudan group. No fossils have yet been found from Dharwarian rocks. Structure: extensive folding and faulting and intense metamorphism.

20. R EFERENCES Precambrian basins of India by Geological society www.geosocindia.com www.shodhganga.com Interpretation of stratigraphy and structure of the Neoarchaean Dharwar Supergroup of rocks in Chitradurga area, Dharwar Craton by Abhinaba Roy, H M Ramachandra & Siladitya Sengupta .(scienceopen.com)