Deposition of the upper Mannville interval (Lower Cretaceous) in the Little Bow-Turin area in southern Alberia occurred on the cratonic side of the Cordilleran foreland basin and evolved in response to changes in base level and sediment supply. Incised-valley fills adn interfluvial paleosols in two stratigraphic units of the upper Mannville interval, the Glauconitic Sandstone and the overlying division A of an upper lithic member, provide evidence for multiple cycles of fluvial incision and subaerial exposure followed by deposition in fluvial, estuarine and costal plain environments. These cycles, which are interpreted to have formed predominantly in response to fluctuations of base level, resulted in stacked, high-frequency, unconformity-bounded sequences. Incised valleys in the Glauconitic Sandstone are filled predominantly with inner to middle estuarine deposits, whereas those in division A are filled predominantly with fluvial deposits. The infills of division A valleys thus formed in a more proximal landward position than those of Glauconitic valleys. Geographic position on the coastal plain therefore had an important influence on the depositional style of the high-frequency sequences. A change in the ratio of sediment supply to creation of accommodation space (supply/space ratio) may also have played a significant role in producing the distinctive depositional differences between Glauconitic and division A sequences. The predominance of estuarine sediments in Glauconitic valleys suggest that facies shifted rapidly landward during valley filling due to a low supply/space ratio. The predominance of fluvial deposits and lesser amounts of estuarine deposits in division A valleys suggest that facies may have shifted more slowly landward during valley filling due to a higher supply/space ratio. An unconformity between the Glauconitic Sandstone and division A marks not only changes in depositional environment and supply/space ratio, but also a change in sand composition from quartzose to lithofeldspathic. These changes reflect tectonically induced changes in palaeogeography and provenance. At the time of deposition of the Glauconitic Sandstone in the study area, a low supply/space ratio allowed an embayment of the Boreal Sea to partly inundate the foredeep trough. The study area, located eastward of the embayment, was supplied predominantly with quartzose sand derived from the craton. At the time of deposition of division A, a higher supply/space ratio resulted in the northward retreat of the Boreal Sea embayment. In the study area, lithofeldspathic sand derived from the Cordillera then overwhelmed any supply of quartzose sand from the craton.