The Lower Cretaceous Viking Formation in the Dodsland-Hoosier area of southwestern Saskatchewan is made up of a series of members which display an interesting depositional pattern. Each Viking member has a marked WSW-ENE linearity which is extremely continuous, some having been traced more than 70 mi (113 km). The most striking feature is the imbricate overlapping of the members, the younger members overlapping toward the south and revealing the small-scale diachronism of the Viking Formation in this area. Deposition of these Viking members from east-flowing tidal currents in a relatively far-from-shore marine environment accounts for their unusual WSW-ENE orientation, which is at a high angle to the more usual NW-SE orientation of the shore and offshore-bar Viking deposi s. It is suggested that the small-scale diachronism of the Viking Formation here is related to southward migration of the tidal currents, possibly because of the modification of the submarine topography by the older deposits.

Although the Viking "sand" in this area has the superficial appearance of a shaly "blanket" sandstone, with patchy development of better reservoir material, detailed well-to-well correlation over the fields shows that all the commercial oil and gas reservoirs are in three Viking members. The strongly developed depositional patterns of the Viking members seem to be unrelated to the present structural attitude of the Viking Formation, but the structure has an important effect on the distribution of oil and gas in the Viking reservoirs. It is suggested that the Viking structure is largely of postdepositional origin, resulting from a combination of compaction-drape structure produced by the weight of post-Viking sediment and solution-collapse features associated with certain Devonian evop rite beds.