Print this pageABSTRACT: Stratigraphic Relationships of Meter-Thick Cycles (Parasequences) to "Third Order Cycles" within the Cambrian Pika, Arctomys and Waterfowl Formations of the Southern Canadian Rocky Mountains: A Case Study
DEMICCO, ROBERT V., S.U.N.Y. at Binghamton, Binghamton, NY, and RON J. SPENCER, University of Calgary, Calgary, Alberta, Canada
The Cambrian Pika, Arctomys, and Waterfowl formations of the southern Canadian Rocky Mountains comprise shallow subtidal, tidal flat, and marginal marine playa facies arranged in six transgressive-regressive sequences each up to 100 m thick and 105 to 106 years in duration. Subtidal facies in the cores of the transgressive-regressive sequences extend variable distances eastward onto the craton and a regional, relative sea level curve can be derived based on this differential backstepping. Sequence stratigraphic models make definite predictions as to how meter-thick cycles (a.k.a. parasequences) should be arranged within transgressive-regressive sequences which we can test against our field data.
We cannot identify meter-thick cycles within subtidal facies. Well-developed, shallowing-upward cycles up to 10 m thick comprise tidal flat facies. Some of these tidal flat cycles can apparently be correlated for up to 150 km across the platform. However, other tidal flat parasequences cannot be traced out across an outcrop and general correlation of cycles is not possible. In some measured sections, tidal flat cycles show decreasing thicknesses toward inferred sequence boundaries and increasing thicknesses away from sequence boundaries. But in other sections of the same interval this may not be the case. The marginal marine playa facies is also composed of meter-thick cycles that cannot be correlated with confidence nor are there any recognizable trends in the thicknesses of these cy les relative to position in a transgressive-regressive sequence. Stratigraphic relations of all meter-thick cycles within this interval are more complex than simple layer-cake predictions of composite eustatic models.
AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)