Superposed Folding in the Northern Part of the Gangpur Series, Orissa

Abstract

Abstract Precambrian metasediments in the northern part of the Gangpur Series, represented by mica schist, phyllite-slate, and schistose quartzite have been investigated over an area of 50 sq km around Lase (22°21' ; 84°45') of Sundargarh district, Orissa. Structural analysis reveals that the earliest folds in bedding (S1) were reclined in nature, but they have been blurred by the profuse development of axial plane schistosity (S2). S2, however, shows upright to slightly overturned folds plunging moderately to E to ESE. The most dominant attitude of S2 nearly normal to the regional fold axis points to the reclined geometry of the folds in S1. Non-penetrative fracture cleavage surfaces (S3) have developed parallel to the axial planes of S2-folds, generally displacing the folded segments. The S3-surfaces, however, show appreciable fanning.