Abstract

The Late Maastrichtian to Early Paleocene fluvial strata of the Scollard, Coalspur, and Willow Creek formations in the Alberta foredeep contain complex and variably abundant authigenic clay mineral assemblages. The authigenic clay minerals in the Scollard sandstones consist mainly of kaolinite and smectite, whereas the Coalspur and the Willow Creek sandstones carry chlorite, chlorite-smectite, dickite, illite, and illite-smectite, with subordinate smectite and kaolinite. The diversity in the distribution of the authigenic clay minerals in the region is not random, but follows basin-scale trends that reflect the burial depth history of these strata. The general absence of dickite, coupled with limited conversion of smectite into illite in the Scollard sandstones, suggests crystallization at depth less than 1.5 km. In contrast, the occurrence of blocky dickite, fibrous illite and chlorite in the Coalspur and Willow Creek sandstones, coupled with albitized feldspars and quartz cement, suggests that sandstones underwent a maximum burial depth greater than 3 km.