|
Original Article |
Geological Studies Unit, Indian Statistical Institute, 203, B.T. Road, Kolkata 700 108, India (e-mail: chandan@isical.ac.in)
The coal-bearing Barakar succession of the Satpura basin is typical of the Gondwanan coal basins of peninsular India, in that it has previously been interpreted as continental in origin. The succession comprises three main facies associations, which are documented within this paper. Medium- to fine-grained muddy sandstone deposits of 5–75 m thickness are reinterpreted as tidally influenced delta deposits. Mudstone deposits of 3–20 m thickness with subordinate sandstones, coals and carbonaceous shales are reinterpreted as delta top deposits, and medium to coarse sandstones of 3–38 m thickness are interpreted as braided delta-top channels. The evidence for tidal influence arises from documentation of bidirectional cross-strata, tidal bundles, tidal rhythmites and periodic variation in foreset thickness. The recognition of tidal deposits indicates marine depositional conditions and significantly changes existing palaeogeographical models. This in turn has important implications for our understanding of the depositional setting and distribution of the Permian coals that occur across much of the southern supercontinent. Furthermore, to the best of the authors' knowledge, coal-bearing tidal-delta deposits have not previously been described from continental interior basins.
Keywords: Gondwana, coal, hummocky cross-stratification, deltaic sedimentation, intertidal sedimentation.
