Uppermost Cretaceous and lower Tertiary rocks in central Alberta include a sequence of largely non-marine sediments which crop out between the eastern provincial boundary and the Foothills belt. On the basis of subtle to obvious differences in lithology, stratigraphic relations, inferred environments of origin, economically important mineral deposits, and the order in which areas were mapped, the rocks were long ago subdivided into several formations, but relationships among units and between areas never were determined satisfactorily. Problems associated with the sequence are of stratigraphic, historical, structural, tectonic, and economic importance.

The marine Bearpaw Formation separates the Belly River Formation (below) from the Edmonton Formation (above) along and east of the Red Deer River and on the North Saskatchewan River. Westward, the Bearpaw thins, tonguing out in the subsurface a short distance west of Red Deer and Leduc. Where the Bearpaw is absent, the Edmonton lies directly upon the Belly River; the entire section, Belly River, Edmonton, and Paskapoo, is non-marine.

Following the lead of Ower (1958) and Elliot (1958), the authors have attempted to trace the Belly River-Edmonton and Edmonton-Paskapoo contacts into the subsurface by means of electric and sample logs. No usefully persistent stratigraphic units that might mark the contacts have been identified. Gross electrical characteristics that have been used for this purpose are not atisfactory.

Portions of the sequence (Brazeau and Paskapoo) that crop out in the Foothills belt include much more sandstone than units that crop out along and east of the Red Deer River. The sandier character of the western sequence is also evident in well logs. The change from more sandy in the west to less so in the east occurs through reduction in number of sandstone bodies, reduction in thickness of sandstone units, and reduction in sandiness of the total section. However, in the eastern part of the subsurface section, distinctly more sandy intervals alternate with distinctly more shaly intervals; the change in character of the sequence is not uniform throughout.

At this stage, it is not possible to establish satisfactory criteria which would enable precise correlation of the subsurface units with the eastern outcrop belt; but it is probable that sandier units crop out and shalier units occupy covered intervals along major river systems.

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