干旱区生态环境知识资源中心

A diverse glossopterid assemblage has been recovered for the first time from the Raniganj Formation (Lopingian) of the Jhingurdah colliery in the Singrauli Coalfield, Son-Mahanadi Basin, Central India. Occupying the northernmost boundary of the Son-Mahanadi master Basin and embodying the last deposits of the Gondwana sedimentation in the northern part of the Peninsular India, the Singrauli Coalfield has the distinction of having the thickest coal seam (Jhingurdah seam- 130m) in India. Complete assemblage consists of five genera with 26 species representing four orders viz., Equisetales (Paracalamites), Cordaitales (Euryphyllum), Cycadales (Macrvtaeniopteris) and Glossopteridales (Glossopteris and Vertebraria). The order Glossopteridales is highly diversified with 23 taxa and the genus Glossopteris with 22 species dominates the flora.

Most of the megafossils are found preserved in the grey shales and mudstones. A large number of vertically or diagonally preserved Vertebraria roots have also been recorded from the beds adjacent to the Glossopteris beds. Thus, the Raniganj beds of Jhingurdah Top Seam represent both allochthonous (horizontally preserved Glossopteris) as well as autochthonous (vertically preserved Vertebraria) preservation at the same place.

Relatively small sized leaves (as compared to the size of similar species reported from the Raniganj or Lower Kamthi formations of other basins/coalfields) of different Glossopteris species in the assemblage indicate semi-arid conditions prevailing in the area during Lopingian; that probably retarded the normal growth of these plants. Such non-congenial climatic conditions also did not allow the glossopterids to blossom as is evidenced by the fact that the entire flora is completely devoid of fructifications. The absence of the groups Lycopodiales, Sphenophyllales, Filicales, Gittkgoales and Coniferales in the assemblage indicates that this palaeogeographic region might not be suitably cool and humid to facilitate the growth of these shade loving under storied plants.