• SILADITYA SENGUPTA

      Articles written in Journal of Earth System Science

    • Interpretation of stratigraphy and structure of the Neoarchaean Dharwar Supergroup of rocks in Chitradurga area, Dharwar Craton

      ABHINABA ROY H M RAMACHANDRA SILADITYA SENGUPTA

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      The Neoarchaean Dharwar Supergroup of rocks in the Chitradurga area unconformably overlie the Mesoarchaean Peninsular Gneissic Complex in the west and are tectonically juxtaposed with Javagondanahalli Schist Belt in the east. The rocks of the supergroup have been divided into older Bababudan and younger Chitradurga Groups. We support the recent division of the Bababudan rocks into a lower conglomerate–sandstone facies association and an upper sandstone–mudstone facies association indicating tidal flat depositional environment. The Talya Conglomerate sequence at the base of the Chitradurga Group is inferred to represent a fault-controlled debris flow deposit. The basin opens out to the east where sedimentation and volcanism took place on an uneven basement surface. The Vanivilas and Ingaldhal Formations likely represent contemporaneous and overlapping sequences indicative of facies variation in space. The KM Kere Conglomerate at the base of the Hiriyur Formation represents a facies series comprising a sequence of volcanic–pyroclastic–volcaniclastic–epiclast association. We propose a four-fold stratigraphic classification with introduction of a new ‘Kantaramanahalli Formation’, placed above the Vanivilas and Ingaldhal Formations and below the Hiriyur Formation. The interpretation of multiple deformed nature of Dharwar Supergroup of rocks and the dominance of the second deformation ($D_{2}$) is supported. The initial irregularities on basement surface and the $F_{1}$ folds have significant role in fold superposition and outcrop patterns. The intra- and interformational ductile shear zones have dominant sinistral transcurrent component. Structural studies are conclusive of simple shear ($D_{2b}$ ) superposed on intense pure shear ($D_{2a}$) indicative of an overall transpressional type of horizontal tectonics.

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