Conodont Biostratigraphy of the Beaverhill Lake Strata, Upper Middle to Lower Upper Devonian, South-Central Alberta

Tom T. Uyeno and Jack C. Wendte
Geological Survey of Canada, Calgary, AB

An integrated study of conodont biostratigraphy and physical stratigraphy/sedimentology has related genetic successions of the Beaverhill Lake strata of south-central Alberta. The study area spans from the eastern shelf through an intervening basin, to the western shelf. This paper reports on the conodont biostratigraphy of, in the central and western parts, basinal successions of the Waterways Formation and foreslope deposits of the Swan Hills Formation, and in the eastern parts, the interstratified shallow-marine and basinal successions of the Beaverhill Lake Formation. The strata, of late Givetian to early Frasnian age, range from 75 to 240 m thick. A total of 974 samples from cores in 49 wells were examined for conodonts, including 131 samples from the Blair Biltmore well (7-11-87-17W4). The biostratigraphy is placed within a T-R sequence-stratigraphic framework.

The Beaverhill Lake strata form most of one overall (first-order) T-R cycle of sedimentation. This overall T-R cycle consists of two major (second-order) T-R cycles, the lower of which extends from the Lower subterminus Fauna to upper MN (Montagne Noire) Zone 2. The upper second-order T-R cycle ranges from upper MN Zone 2 to MN Zone 4. The study suggests that there was continuous sedimentation through the Givetian-Frasnian (Middle-Late Devonian) boundary. The base of MN Zone 4 was determined by the first occurrence of a new species of Ancyrodella, that has been demonstrated to be restricted to that zone through graphic correlation (Klapper, pers. comm., 2000).

The correlations made independently from physical sequence stratigraphy and conodont biostratigraphy corroborate each other.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005