Tuesday, December 30, 2014

Evidence of Tidal Deposits From NeoArchean India

Late Archean tidalites from western margin of Chitradurga Greenstone Belt, southern India


Bhattacharya et al


Tidalites are preserved within a metavolcano-sedimentary succession of the Late Archean Bababudan Group (Dharwar Supergroup) along the western boundary of the NNW-SSE trending Chitradurga greenstone belt, West Dharwar Craton, southern India. These may represent the oldest record of tidal processes in peninsular India. Millimetre thick sand-mud alternations, bidirectional cross-strata, mudstone-draped sandy foresets, reactivation surfaces indicating time-velocity asymmetry, sigmoidal cross-strata and mudstone draped flaser/lenticular bedding are displayed by the sandstone mudstone heterolithic facies in the upper part of the Bababudan succession, together implying a tidal depositional system. Thick-thin pairs of rhythmic foreset bundles correspond to neap-spring tidal cycles within a semidiurnal tidal system. Development of the studied coastal sediments suggests formation of stable platform along the western margin of the late Archean Chitradurga greenstone belt.

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