• Aditya U Joshi

      Articles written in Journal of Earth System Science

    • Rootless calc-silicate folds in granite: An implication towards syn- to post-plutonic emplacement

      Aditya U Joshi Manoj A Limaye

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      Deformation of the Champaner Group of rocks that form a part of Southern Aravalli Mountain Belt, western India, occurred during the Grenville orogeny (ca. 1400–935 Ma). Two phases of deformation are recorded: D1, persistent throughout the group and characterised by westerly plunging tight isoclinal foldsand D2, a localized phase of deformation associated with shortening of the earlier folds from the eastern margin. Both the phases of deformation are in association with the syn-tectonically emplaced Godhra granite. The present work records rootless calc-silicate folds in granite belonging to the older formation,located at the eastern fringe of the Champaner Group. Field evidences suggest superimposition of Type 2 interference pattern trending NE–SW over rootless Type 0 of varying trends from NW–SE to N–S. The superposed pattern obtained from the field study differs in terms of structural trends with the neighbouring Precambrian stratigraphic units. These stratigraphic units include the Champaner Group to which the study area belongs, the Kadana Formation of the Lunavada Group and Pre-Chamapaner Gneissic Complex. Rootless character of folds found within the study area imply syn-post plutonic emplacement of Godhra granite.

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

      Aditya U Joshi

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      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.

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