Microflora of the Lower Cretaceous Mannville Group, East-Central Alberta

Three cored sections of the Lower Cretaceous Mannville Group from the subsurface of east-central Alberta were sampled for their microfloral content. The microflora recovered contains 53 genera and 120 species of microspores and pollen, 10 genera and 23 species of megaspores, 8 genera and 16 species of marine microplankton, and specimens described as seeds. Sixteen microspore and pollen species, 7 megaspore species, and a microplankton species are new. The spore and pollen species are attributed to a megaflora composed of bryophytes, ferns, pteridosperms, cycads, and conifers; no angiosperm microfloral elements are present.

The Mannville microflora shows a complete gradation in evolutionary succession. The flora of the lower, continental McMurray Formation contains elements of the Wealden Arcellites [Pyrobolospora] flora, which shows that the base of the Mannville Group in east-central Alberta is not older than late Barremian. The microflora of the basal Deville Member is dated as late Barremian, and that of the overlying Ellerslie Member as Aptian. The upper 'calcareous' member contains no diagnostic index species but is dated from its stratigraphic position as early to early middle Albian.

The microflora of the upper part of the Mannville Group, including the marine Clearwater and marine to continental Grand Rapids Formations, contains index species of Albian age, which support the middle Albian age assigned to these units on the basis of other fossil evidence.

The distribution of microplankton indicates a continental origin for the McMurray Formation.