| The Lower Cretaceous Clearwater Formation in east-central Alberta contains the second largest oil sands deposit in Canada. In the Cold Lake area, 43 cored intervals were examined and classified based on physical and biogenic sedimentary structures. Core analysis and stratigraphic mapping determined that the Clearwater Formation consists predominantely of stacked tidally-dominated strata that prograde to the north into the Boreal Seaway. The trace fossil assemblages observed show evidence of somewhat stressed conditions, indicated by the more restricted and diminished ichnofauna. However, higher ichnodiversity, larger trace sizes and the predominance of more fully marine forms support sediment deposition in a deltaic system. The stratigraphic framework of the Clearwater Formation was redefined using allostratigraphy. Five allomembers were identified reflecting a series of transgressive-regressive cycles of relative sea-level rise and fall, retrogradation of the shoreline and progradation of tide-dominated deltaic sediments in the study area. |
