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

S. Mohanty ¹, K. Naha ²

Affiliations
1 Department of Applied Geology, Indian School of Mines, Dhanbad 826004, IN
2 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur 721302., IN

Abstract

Around Salumbar in the Udaipur district, Rajasthan, the Banded Gneissic Complex (BGC). the Aravalli metasedimentary rocks, the Dudar Gneiss and the Lakapa Granite Gneiss have been involved in the same style and sequence of muhiple deformation. The oldest rocks are the migmatites forming the BGC, which underlie the Aravalli metasediments with an unconformity marked by a conglomerate. Rare relict pre-Aravalli structures in the BGC, and the conglomerate containing gneissic pebbles provide incontrovertible evidence for a part of the BGC being the original basement. Identical structural style and sequence of the basement gneisses wilh those of the metasedimentary cover rocks, however, point to mobilization so that they could take part in the earliest deformation affecting the metasediments in a ductile manner. The Dudar Gneiss has formed by migmatization of the Aravalli rocks synkinematically with the first deformation, whereas the Lakapa Granite Gneiss has been emplaced as a syn-to late-tectonic intrusion.

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S. Mohanty ¹

Affiliations
1 Department of Applied Geology, Indian School of Mines, Dhanbad 826 004, IN

Abstract

In the Precambrian terrane of central India the question of the relation between different gneiss and schist belts has not been solved. Eventhough the Tirodi gneiss is generally considered to be the basement of the Sausar Group, unequivocal sedimentological criteria are not supplemented to confirm this view. A conglomerate which belongs to the Sausar Group has been mapped at the contact of a gneissic roc in the Mansar area of Nagpur district, Maharashtra, during the present investigation. Occurrence of gneiss pebbles in this conglomerate suggests that the gneissic unit was the source of the pebbles and acted as the basement to the Sausar Group.

Keywords

Basement, Unconformity, Sausar Group, Central India Maharashtra, Stratigraphy.

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A. K. Mohanty ¹, S. Mohanty ¹

Affiliations
1 Department of Applied Geology, Indian School of Mines, Dhanbad - 826 004, IN

Abstract

The Precambrian rocks of the Mansar area, Nagpur district, Maharashtra, belong to the Sausar Group and the Tirodi Gneiss. Both these lithological units show an unconformable relation in the area, marked by a conglomerate at the base of the Sausar Group. The metasediments of the Sausar Group bear imprints of polyphase deformation. The folds of the first generation (F₁) are isoclinal with high amplitude to wavelength ratios and pervasive axial planar cleavage (S₁). The structures of the second generation are represented by WNW-ESE trending upright isoclinal folds (F₂) and axial planar crenulation cleavage (S₂). Gentle upright folds with NE-SW striking axial planes represent structures of the third generation (F₃) Superposition of F₂ folds on F₁ folds is marked by mushroom shaped interference pattern in small-scale. Because of upright isoclinal nature of F₂ folds on WNW-ESE striking axial planes, the metasedimentary bands extend in E-W direction. Slight arcuate geometry of the metasedimentary bands is the result of superposition of F₃ folds on F₁/F₂ folds.

Keywords

Structural Geology, Sausar Group, Unconformity, Nagpur Dist., Maharashtra.

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S. Mohanty ¹

Affiliations
1 Department of Applied Geology, Indian School of Mines, Dhanbad-826004, IN

Abstract

No Abstract.

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S. Mohanty ¹

Affiliations
1 Department of Applied Geology, Indian School of Mines, Dhanbad - 826 004, IN

Abstract

Palaeoproterozoic rocks of the Sausar Group, central India, are exposed on the southern flank of the Satpura Mountain Belt. Mapping in different parts of this belt indicates complex evolutionary history. The presence of a volcanosedimentary unit in the basal part of the Sausar Group is reported here. The sedimentological characters of the overlying unit indicate its glaciogenic origin. Association of volcanogenic and glaciogenic rocks in the Sausar Group could be used as tectonostratigraphic tool for supercontinent assembly during Palaeoproterozoic.

Keywords

Palaeoproterozoic Glaciation, Volcanism, Sausar Group, Central India.

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S. Mohanty ¹

Affiliations
1 Department of Applied Geology, Indian School of Mines, Dhanbad - 826 004, IN

Abstract

Precambrian metasediments of Parseoni area belong to the Sausar Group. These comprise of quartzite, mica schist with manganese ore and marble. The metasediments of the area show evidence of three phases of folding. The early folds (F₁) are isoclinal with an axial planar cleavage (S₁). The second folds (F₂) are tight to isoclinal with axial planar crenulation cleavage (S₂). Thcse F₂ folds have EW striking vertical axial planes and congruous pucker axis lineations. The third folds (F₃) are open upright with NS striking axial planes. An antiformal F₂ fold plunging E is mapped in the area. In the absence of any primary top-and-bottom criteria the stratigraphic succession for the area suggested by earlier workers is debatable.

Keywords

Precambrian Geology, Stratigraphic Succession, Sausar Group, Superposed Folding, Manganese Ore, Maharashtra.

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