Foraminiferal response to Albian relative sea-level changes in northwestern and central Alberta, Canada

Albian foraminiferal assemblages from three wells in northwestern (Imperial Spirit River No. 1, 12-20-78-6W6), central (AngloHome C&E Fort Augustus No . 1, 7-29-55-21W4), and southern Alberta (Amoco B1 Youngstown, 6-34-30-8W4) provide the basis to track a fluctuating sea-level history in western Cana da. Two global second-order marine cycles (Kiowa - Skull Creek and Greenhor n) were punctuated by higher frequency relative sea-level cycles expressed during the time of the Moosebar-Clearwater, Hulcross, Joli Fou, and Mowry s eas. A total of 34 genera and 93 subgeneric taxa are recognized in these Al bian-age strata. Foraminiferal abundance and species diversity of the lates t Albian Mowry Sea were higher than in the early to middle Albian Moosebar- Clearwater and Hulcross seas. The two earliest paleo-seas were shallow emba yments of the Boreal Sea, and relative sea-level fluctuations caused variab le marine to brackish conditions expressed in a variety of faunal assemblag es. Towards the late Albian, relative sea level rose, deepening the basin a nd establishing increased marine conditions and more favourable habitats fo r foraminifera. In the deeper Joli Fou Seaway and Mowry Sea, however, reduc ed bottom water oxygen through stratification or stagnant circulation cause d times of diminished benthic faunas. The Bluesky Formation in northwestern Alberta contains the initial transgression of the early Albian Moosebar-Cl earwater Sea and is marked by a sudden faunal increase. In contrast, transg ression by the late late Albian Mowry Sea was associated with a gradual inc rease of foraminiferal faunas. Numerous agglutinated species range througho ut the entire Albian, absent only at times of basin shallowing. However, ea ch major marine incursion throughout the Albian introduced new taxa.