Fold interference patterns in Meso-Proterozoic Champaner fold belt (CFB) Gujarat, western India

Abstract

This paper documents three phases of folding within the Meso-Proterozoic Champaner Fold Belt (CFB) located at the eastern part of Gujarat, western India. The first phase (F 1 ) displays WNW plunging F 1 fold of moderately inclined nature in the schists of the Khandia Formation. The second phase (F 2 ) refolded F 1 along a similar trend to produce folds of tight isoclinal nature in the Khandia and Narukot quartzites. Additionally, these F 1 folds depict second-order tight, and F 2 folds as first-order open type in the younger sequences of the CFB with varying amplitude vs. wavelength ratio. The ratio for F 1 folds ranges from 2:1 to 3:1, obtained along 3–4 m length across 3–6 m 2 area, whereas for F 2 folds the ratio ranges from 1:4 to 1:5 and is obtained along 1–2.5 km length across 0.5–1.5 km 2 area. The fold interference pattern developed on account of F 1 and F 2 folds has resulted into Type-III or hook-shaped geometry regionally. The last phase of folding is characterised by N–S trending F 3 folds of open type over kilometre long limbs of F 1 and F 2 folds. The superposition of F 1 - 3 folds developed map scale Type-I or Dome and Basin geometry over Type-III superposed folds. The overall compressional direction for F 1 and F 2 folds ranges from N–S to NNE–SSW and for F 3 ranges from E–W to ESE–WNW.