Abstract Examination of the trace fossil assemblages associated with the Albian Wabiskaw Member and the Clearwater Formation in the Marten Hill gas field in north-central Alberta, has proven valuable in reconstructing the depositional environment responsible for it's deposition. The diverse and well preserved suite of trace fossils record the initial marine transgression of the Boreal Sea.

Abstract Palynofloral assemblages associated with strata of the McMurray Formation, Wabiskaw Member, and Clearwater Formation can be placed into a classification scheme based primarily on dinocyst content. Although most of the palynofloral assemblages are dominated by terrestrially derived pollen and spores, the dinocysts can be used to characterize fresh water through a marine continuum in which to place these diverse paleoenvironments. Freshwater and slightly brackish paleoenvironments are most characteristic of the McMurray Formation, whereas stressed, shoreface, and nearshore paleoenvironments are most characteristic of the Wabiskaw Member and Clearwater Formation strata. Dinocyst assemblages from the McMurray Formation are characterized by the freshwater algae Hurlandsia rugara and rare Holmewoodinium sp., with varying abundances of Nyktericysta spp. group dinocysts. The relative abundance and diversity of these Nyktericysta spp. dinocysts can be correlated with increased brackish influence. Locally within the McMurray Formation, the presence of Vesperopsis spp. may indicate significant brackish influence.Within the overlying Wabiskaw Member and Clearwater Formation, dinocyst assemblages are indicative of the southward-transgressing Clearwater Sea. Assemblages may be dominated by species of Circulodinium (C. deflandrei and C. brevispinosum), Odontochitina operculata, Oligosphaeridium spp., Palaeoperidinium cretaceum plus a host of accessory taxa indicative of stressed paleoenvironments, including several new undescribed species. Significantly, the distribution and nature of the palynofloral assemblages do not validate the historic threefold division of the McMurray Formation into lower, middle, and uppermembers, nor do the palynofloral assemblages reflect a gradual upward increase in marine influence. Instead, the palynofloral assemblages indicate much more regionally diverse paleoenvironments, with brackish influence recognized throughout.

Abstract The Lower Cretaceous oil sands in the Primrose-Kirby area occur in two superimposed, and geologically very different, reservoir units. The lower reservoir unit is the McMurray Formation, with facies changing from a fully terrestrial, fluvial environment at the base to a marginally marine, deltaic environment with major channels near the top. The Wabiskaw Member of the Clearwater Formation forms the upper reservoir unit, with laterally continuous marine sheet sands. The contact between the McMurray Formation and the Wabiskaw Member marks the transgression of the area, generally from the north, by the boreal sea. The two reservoirs have very different characteristics, as was revealed by detailed sedimentological, mineralogical, biostratigraphical, and particle size analyses. The channel sands in the McMurray Formation form the most favorable reservoirs because the unconsolidated sands are relatively coarse-grained and well-sorted homogeneous quartzarenites to sublitharenites with no significant amounts of clay minerals or glauconite. The channels are 30-40 m (100-130 ft) thick and have an average bitumen content of 11. 2 wt %. The Wabiskaw sediments are finer grained and more poorly sorted heterogeneous litharenites containing significant amounts of fines. In addition, numerous carbonate-cemented, totally indurated zones, up to 1 m (3 ft) thick, occur. The average bitumen content is relatively low (9. 5 wt %), but the very continuous and predictable thickness of approximately 20 m (65 ft) makes the Wabiskaw a very attractive reservoir. Both McMurray channel sands and Wabiskaw marine sheet sands with a combined total of 700 million barrels of exploitable bitumen in place in the study area are being tested for performance. The promising preliminary results of both reservoir units indicate that the general Primrose area may provide a significant amount of Alberta’s future oil production.