• Shilpa Patil Pillai

      Articles written in Journal of Earth System Science

    • Implications of new ⁴⁰Ar / ³⁸Ar age of Mallapur Intrusives on the chronology and evolution of the Kaladgi Basin, Dharwar Craton, India

      Shilpa Patil Pillai Kanchan Pande Vivek S Kale

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      The Kaladgi Basin on the northern edge of the Dharwar craton has characters diverse from the other epicratonic Purana basins of Peninsular India. Sedimentological studies in the basin have established the presence of three cycles of flooding separated by an event of intra-basinal deformation accompaniedby low grade incipient metamorphism. The overall structural configuration of the basin indicates its development by supracrustal extension accompanied by shearing in a trans-tensional regime during the Mesoproterozoic. This was followed by sagging that yielded Neoproterozoic sedimentation in a successornested basin. ⁴⁰Ar / ³⁸Ar dating

      of an intrusive mafic dyke along the axial plane of a fold has yielded a plateau age of 1154±4Ma. This helps constraint the age of the various events during the evolution of this basin.

    • Geometry and age of a mafic dyke emplaced along the Bhetkheda–Mohana Lineament, Central Narmada valley, Deccan Volcanic Province


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      The Bhetkheda–Mohana Lineament is traced as a continuous lineament across nearly 100 km in the central Narmada valley across the Deccan Trap basalts and their basement of Proterozoic sediments. While a major length of this lineament is occupied by a basaltic dyke, there are segments where the dyke is completely absent, and the lineament is represented by a regional fracture/shear/fault zone. At its eastern extremity, this dyke is exposed intruding along the axis of a synclinorium of the Vindhyan Supergroup sediments, as a 4-km long string of hillocks of picturesque columnar jointed basalt. It has the presence of ignimbrites and a thin basaltic flow (resting on the sediments) surrounding it, suggesting the presence of an eruptive vent. This dyke intrudes the Mandleshwar Formation lava flows dated at 67–66 Ma and is associated with the Narmada dyke swarm. It has given $^{40}$Ar/$^{39}$Ar age of 66.6±0.5 Ma. Its chemical characters conform to those of the basaltic flows of the Malwa Traps, indicating a common source and emplacement history. This is a unique example of a dyke that was emplaced along a preexisting fracture zone cutting through the Proterozoic basement as well as the Deccan Trap lavas, with a distinct petrological identity with the host lava flows, indicating its feeder relation. It endorses the comparison of the Icelandic mode of fissure-fed flood basalts with the eruptive history of the Deccan Volcanic Province.

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