Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

D. K. Bhatt ¹, Gopal Singh ², Sumant Gupta ², M. K. Soni ³, A. K. Moitra ⁴, D. P. Das ⁵, C. De ⁵

Affiliations
1 Geological Survey of India, Jaipur 320004, IN
2 Geological Survey of India, Lucknow 226024, IN
3 Geological Survey of India, Jabalpur 482003, IN
4 Geological Survey of India, Hyderabad 500068, IN
5 Geological Survey of India, Calcutta 700016, IN

Abstract

No Abstract.

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A. K. Moitra ¹

Affiliations
1 Geological Survey of India, Palaeontology Division, 15, Kyd street, Calcutta - 700 016, IN

Abstract

The Proterozoic Chhattisgarh basin, comprising 2000m thick sediments mainly limestonel/dolomite, sandstone and shale, shows prolific growth of stromatolites and presence of micro biota dominantly cyanobacteria. Added to these there are many sedimentary features and structures found in the rocks throughoutthe sequence. Depositional environment is thus well doculnented by physicochemical factors in general and biological features in particular.

Based on all these biogeological features, it has been deduced that the deposition is largely marine under tidal flat conditions, sources of sediments being both precipitation as well as terrigenous material. Sedimentation shows a distinct cyclic pattern commencing with arenaceous facies culminating into argillaceous facies with intervening calcareous facies. During the waning stage of sedimentary history of the Chhattisgarh basin, the cycles repeated rapidly, interpreted from the intercalatory sedimentation of the upper horizon, namely Raipur Limestone. Disposition of stromatolites ancLtheir morphologies reveal low as well as high-energy conditions of deposition, levels of deposition being both intertidal and subtidal ones. The sedimentological, mineralogical and petrological evidences point towards an alternating oxidising and reducing environments throughout the sequence irrespective of cycles or lithologies.

Overwhelming dominance of procaryotic algae and absence (7 or near absence) of eucaryotic algae have possibly the following implications, namely the temperature during deposition was raised above 40°C at least for major part during deposition and also the pH of the environment. was 7 or more.

Keywords

Sedimentology, Palaeontology, Stromatolites, Chhattisgarh Basin, Madhya Pradesh.

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T. T. Nath ¹, P. Yadagiri ¹, A. K. Moitra ¹

Affiliations
1 Geological Survey of India, Southern Region, Hyderabad - 500 068, IN

Abstract

For the first time, skeletal remains of an armoured dinosaur (Ornithischia: Ankylosauria) were found in the red clay bed of the Kota Formation, Pranhita-Godavari Valley, Andhra Pradesh. The bed occurs 2 m below the marker limestone unit of the Kota Formation. The collection includes parts of skull, 30 specimens of body armour, vertebrae and parts of girdle bones. The characteristics of armour plates, skull and teeth indicate that these fossils belong to ankylosauria. The ankylosaurs are less known from the Lower Jurassic period. The detailed studies of the present material are likely to throw light on the evolutionary history of these dinosaurs.

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