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

P. K. Saraswati ¹, N. Pandey ²

Affiliations
1 Indian Institute of Technology, Mumbai, IN
2 Nagaland University Medziphem, IN

Abstract

No Abstract.

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N. Pandey ¹, B. K. Chatterjee ¹

Affiliations
1 Department of Geology, Banaras Hindu University, Varanasi 221005, IN

Abstract

The Precambrian Banded Iron Formation of Gandhamardan hill, Keonjhar district, Orissa, belongs to Noamundi Group. It is restricted largely to oxide facies of Lake Superior type. The sulphide facies in association with black chert is present in small amount. It is almost unmetamorphosed and exhibits many depositional and penecontemporaneous deformation sedimentary structures. A preliminary field and petrographic examination reveals that iron formation was initially deposited at least in major part as hematite-magnetite-chert rock in a near-shore epicontinental environment partially restricted from free-circulation of sea water. Iron and silica were precipitated almost contemporaneously largely due to physico-chemical changes in sea water. The presence of siliceous stromatolitic laminations and alga-like spheroid Archaeospheroides barbertonis similar to that of Fig Tree cherts, however, suggests biogenic activity during the deposition of the Banded Iron Formation.

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S. K. Srivastava ¹, N. Pandey ²

Affiliations
1 Department of Geology, Nagaland University, Kohima - 797 002, IN
2 Department of Earth Science, Assam University, Silchar - 788 011, IN

Abstract

Provenance of the Oligocene Barail sandstones has been ascertained by means of petrographic and heavy mineral studies. Petrography reveals an abundance of angular to sub-rounded monocrystalline, non-undulatory quartz followed by lithic fragments. The overall composition of sandstones matches with those of sublith-arenites. The heavy mineral suite of Barail sandstones displays rounded to sub-rounded as well as euhedral/angular grains of iron oxide, zircon, tourmaline, rutile, kyanite, sillimanite and staurolite in decreasing order of abundance. Petrography coupled with heavy mineral suite suggests for a mixed provenance dominated by a sedimentary source of recycled orogenic provenance in a foreland basin setup.

Keywords

Petrography, Heavy Minerals, Provenance, Barail Group, Nagaland.

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