Ichnology and Paleoecology of the Upper Cretaceous Cardium Formation at Seebe, Alberta

Abstract

<p>The Cardium at Seebe is definable in terms of five ichnofacies which correlate with the twelve sedimentological facies of Wright (1980). A revised species list of the ichnofauna has been constructed and is used along with sedimentological data to develop the paleoenvironment at Seebe. The five ichnofacies differ in grain size, sediment type and degree of bioturbation. Totally bioturbated sands and shales reflect long periods of environmental stability during which communities of varying diversity were established. Where traces are preserved best, namely on the upper surfaces of the previously defined cycles 2 and 3, community analyses were performed. These analyses indicate a general correlation between diversity and environmental stability following the storm deposition of sands. Conditions under which non-bioturbated sands were deposited are also discussed. This is the first analysis of the ichnofauna at Seebe and as such it includes a detailed study of the systematic ichnology of the area. Ichnologically, the Cardium at Seebe represents a mid-shelf environment populated largely by deposit feeders. The ichnocoenoses are within the Cruziana-Zoophycos assemblage which is characteristic of deeper water. These are best developed on the upper surfaces of the storm dominated sands. The paleoecological observations are concurrent with Wright's sedimentological observations in as much as they suggest an open marine rather than a nearshore environment.</p>