Sedimentology and depositional history of Lower Cretaceous coarse-grained clastics, Southwest Alberta and Southeast British Columbia

The Lower Cretaceous Cadomin Formation has been traditionally subdivided into the Pocaterra Creek Member and overlying undifferentiated Cadomin. The Cadomin Formation in southwestern Alberta is a relatively thin, aerially extensive, sheet of conglomerate. In outcrop, a previously unrecognized sandstone unit overlying the Cadomin Formation is described and named the Dalhousie Formation, using nearby subsurface terminology. The Dalhousie Formation was previously considered to be a facies variation of the Cadomin Formation. Paleocurrent data from the Elk Formation, the Pocaterra Creek Member and Cadomin Formation consistently indicate northerly paleocurrents, subparallel to the rising cordillera. The Cadomin and Dalhousie formations were deposited as braided river deposits on a north-dipping paleoslope. A series of unconformities is associated with the Pocaterra Creek Member, Cadomin Formation and Dalhousie Formation. The units each become younger and more extensive laterally to the east and each unconformity becomes more regionally extensive. The unconformities merge eastwards and westwards into a composite surface that represents the basal Cretaceous unconformity.