Quartzose sandstones of the lower part of the Mannville Group in east-central Alberta are generally referred to as the Ellerslie Formation (Member). They are considered to be the deposits of a Lower Cretaceous fluvio-deltaic complex which overlies the "Pre-Cretaceous" unconformity in western Canada. In west-central Alberta, other quartzose sandstone units can be present beneath the Ellerslie. Some workers have included these units within the Mannville, others have attempted to map them separately. The result has been general confusion.

The trend and origin of different sandstone bodies can be compared in the Medicine River area. Here, two unconformity-bounded units--the UJ2 and UJ3 of Ter Berg (1966)--fill a deep valley cut into Lower Jurassic and Mississippian strata, and are overlain by the Ellerslie.

Ellerslie sediments blanket the area and are productive from quartzarenites in a number of isolated pools. Productive sandstone bodies encompass a variety of small estuarine, shoreline, and tidal ridge deposits, none of whose trends relate to the configuration of that old favorite, the eroded surface of underlying Mississippian strata.

Comparison of quartzose sandstone units in the Medicine River area with similar sandstone units elsewhere in Alberta, Saskatchewan, and Montana, indicates that the Ellerslie was deposited in a vast inland sea into which several large deltas prograded. UJ2 and UJ3 sandstones are similar to those of the Success and Morrison formations of Saskatchewan and Montana, respectively.

Similar sandstone deposits can be anticipated along the eastern margin of the Alberta trough, in south and central Alberta. Where quartzarenites are present, they will have resisted diagenetic porosity destruction, and will form attractive reservoirs.

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