• M Venkateshwarlu

      Articles written in Journal of Earth System Science

    • Petrography and geochemistry of Jurassic sandstones from the Jhuran Formation of Jara dome, Kachchh basin, India: Implications for provenance and tectonic setting

      V Periasamy M Venkateshwarlu

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      Sandstones of Jhuran Formation from Jara dome, western Kachchh, Gujarat, India were studied for major, trace and rare earth element (REE) geochemistry to deduce their paleo-weathering, tectonic setting, source rock characteristics and provenance. Petrographic analysis shows that sandstones are having quartz grains with minor amount of K-feldspar and lithic fragments in the modal ratio of Q89:F7:L4. On the basis of geochemical results, sandstones are classified into arkose, sub-litharenite, wacke and quartz arenite. The corrected CIA values indicate that the weathering at source region was moderate to intense. The distribution of major and REE elements in the samples normalized to upper continental crust (UCC) and chondrite values indicate similar pattern of UCC. The tectonic discrimination diagram based on the elemental concentrations and elemental ratios of Fe2O3+MgO vs. TiO2, SiO2 vs. log(K2O/Na2O), Sc/Cr vs. La/Y, Th–Sc–Zr/10, La–Th–Sc plots Jhuran Formation samples in continental rift and collision settings. The plots of Ni against TiO2, La/Sc vs. Th/Co and V–Ni–Th∗10 reveals that the sediments of Jhuran Formation were derived from felsic rock sources. Additionally, the diagram of (Gd/Yb)N against Eu/Eu suggest the post-Archean provenance as source possibly Nagar Parkar complex for the studied samples.

    • New paleomagnetic results on ~2367 Ma Dharwar giant dyke swarm, Dharwar craton, southern India: implications for Paleoproterozoic continental reconstruction

      N Ramesh Babu M Venkateshwarlu Ravi Shankar E Nagaraju V Parashuramulu

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      Here we report new paleomagnetic results and precise paleopole position of the extensional study on ~ 2367 Ma mafic giant radiating dyke swarm in the Dharwar craton, southern India. We have sampled 29 sites on 12 dykes from NE–SW Karimnagar–Hyderabad dykes and Dhone–Gooty sector dykes, eastern Dharwar craton to provide unambiguous paleomagnetism evidence on the spectacular radiating dyke swarm and thereby strengthening the presence of single magmatic event at ~ 2367 Ma. A total of 158 samples were subjected to detailed alternating field and thermal demagnetization techniques and the results are presented here along with previously reported data on the same dyke swarm. The remanent magnetic directions are showing two components, viz., seven sites representing four dykes show component (A) with mean declination of 94◦ and mean inclination of −70◦ (k = 87, α95 = 10◦) and corresponding paleopole at 16◦N, 41◦E (dp = 15◦ and dm = 17◦) and 22 sites representing 8 dykes yielded a component (B) with mean declination of 41◦ and mean inclination of −21◦ (k = 41, α95 = 9◦) with a paleopole at 41◦N, 200◦E (dp = 5◦ and dm = 10◦). Component (A) results are similar to the previously reported directions from the ~ 2367 Ma dyke swarm, which have been confirmed fairly reliably to be of primary origin. The component (B) directions appear to be strongly overprinted by the 2080 Ma event. The grand mean for the primary component (A) combined with earlier reported studies gives mean declination of 97◦ and mean inclination of −79◦ (k = 55, α95 = 3◦) with a paleopole at 15◦N, 57◦E (dp = 5◦, dm = 6◦). Paleogeographical position for the Dharwar craton at ~ 2367 Ma suggests that there may be a chance to possible spatial link between Dharwar dykes of Dharwar craton (India), Widgemooltha and Erayinia dykes of Yilgarn craton (Australia), Sebanga Poort Dykes of Zimbabwe craton (Africa) and Karelian dykes of Kola-Karelia craton (Baltica Shield).

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