STRATIGRAPHY, STRUCTURE AND SYNTECTONIC SEDIMENTATION OF THE CAMPANIAN BELLY RIVER CLASTIC WEDGE IN THE SOUTHERN CANADIAN CORDILLERA

The parautochthonous, subproximal segment of the 'Belly River' clastic wedge is subdivided into five new formations, listed here from oldest to youngest: Lees Lake, Burmis, Connelly Creek, Lundbreck and Drywood Creek. The Pakowki Formation divides the 'Belly River' clastic wedge into a lower succession consisting of predominantly marine sediments ( the Lees Lake and Burmis Formations) and an upper succession (the Conn elly Creek, Lundbreck and Drywood Creek Formations). The lower success ion including the Pakowki Formation belongs to the Alberta Group and t he upper succession represents the Belly River Group. The formations h ave been mapped in the Foreland Thrust and Fold Belt west of Lundbreck , Alberta, and correlated with the subsurface distal, autochthonous fo rmations of the Interior Platform. Early indications of Laramide tecto nic activity in the source area are recorded by the turbidites of the Lees Lake Formation. An increase in the supply of sand during depositi on of the Lees Lake Formation produced thick sandstone layers which we re syndepositionally deformed and partly eroded by sediment-laden dens ity currents. The contact between the Lees Lake Formation and the over lying Burmis Formation is unconformable because of submarine erosion. The Burmis Formation is recognized as a deltaic sequence containing a lateral transition from fluviatile through distributary channel-fill t o distributary mouth-bar facies. The next phase of the Laramide Orogen y is recorded by the upper delta plain facies of the Connelly Creek Fo rmation and the alluvial fan facies of the Lundbreck Formation. The fa n-shape geometry and sedimentological features of the Lundbreck Format ion, especially the ephemeral, high-energy channels, semi-arid paleoso ls and playa deposits indicate sedimentation on a semi-arid alluvial f an bordering the upper delta plain environment. Flash-flood deposition within the ephemeral channels and deep erosion of the alluvial plain during sedimentation of the Lundbreck Formation suggest significant sy ndepositional topography. The semi-arid alluvial fan environment sugge sted for the Lundbreck Formation implies an uplifted mountain front du ring its formation. Basinward progradation of the Connelly Creek/Lundb reck delta was caused by easterly propagation of the tectonic deformat ion that forced the Pakowki Sea to retreat from the Crowsnest Embaymen t.