Algal stromatolites from the krol formation of the Mussoorie syncline, Uttar Pradesh

Abstract

The results of the study of the Algal stromatolites associated with phosphorite occurring in the top most member of the Krol Formation, the Mussoorie Phosphorite Member, which overlies the light grey dolomitic limestones, known as the Upper Krol Limestones, near Mussoorie in the Dehra Dun District of Uttar Pradesh have been recorded in the paper. The types of stromatolites that have so far been recognized from these are: (i) spheroidal or nodular (Oncolithes), (ii) conical cup shaped, (iii) cylindrical columnar branching upwards, (iv) laterally connected columns, (v) cylindrical columnar with detached columns. Excepting the first one which is rounded and without any root, the rest of the structures appear to be varieties of Collenia. The significance of the association of these algal stromatolites on the genesis of the phosphorite and the environment of deposition is obvious as the presence of these stromatolites indicate shallow intertidal to subtidal marine condition.

The oncolites present in this horizon appear to have affinity with the Late Palaeozoic to early Mesozoic forms. The columnar forms have to be defined and named properly for distinguishing them from the Proterozoic ones. The type (iv) form compares very well with the form Malacostroma concentricum (Gurich) reported from the Mississippian of Belgium (Johnson, 1961).