Abstract

The calcareous constituents of the Lower Limestone and the Upper Sandy Limestone of the Lameta Group of Central India are largely of algal origin. These rocks were deposited under intertidal to inner-neritic marine waters. Tidal recession at times exposed the intertidal mudflats to atmosphere and desiccation and is responsible for formation of oxidized limeclasts. The algal limestones overlying the continental fresh-water deposits of the Jabalpur Group (Gondwana Supergroup) indicate a persistence of the depositional interface and in turn suggest that pre-Lameta tectonism did not result in a great change of elevation of the area. Recrystallization of intraclasts has been demonstrated to be a penecontemporaneous phenomenon. Discretely recrystallized carbonate rock fragments in an unrecrystallized host is thus an untrustworthy criterion of their extraenvironmental origin. Occurrence of extraformational and yet intrabasinal limeclasts in these rocks confirms the desirability of the genetic distinction of extraformational and extrabasinal limeclasts. On the basis of independent evidence, it has been demonstrated that open-space structures are good shallow-water indicators and helpful in delineating ancient shorelines. These data substantiate some of the observations by Wolf (1965b).

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