STRATIGRAPHIC ARCHITECTURE OF THE FRASNIAN SOUTH JASPER BASIN, NORTH-CENTRAL ALBERTA FRONT RANGES
John A.W. Weissenberger, Pak K. Wong, Murray G. Gilhooly, 2017. "STRATIGRAPHIC ARCHITECTURE OF THE FRASNIAN SOUTH JASPER BASIN, NORTH-CENTRAL ALBERTA FRONT RANGES", NEWADVANCES IN DEVONIAN CARBONATES: OUTCROP ANALOGS, RESERVOIRS AND CHRONOSTRATIGRAPHY, Ted E. Playton, Charles Kerans, John A.W. Weissenberger
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The South Jasper Basin was a major locus of carbonate deposition during the Frasnian, and its sedimentary record is extensively exposed in the Alberta Rocky Mountains. This study places many of its classic outcrops into a sequence stratigraphic framework for the first time. New descriptions of 18 outcrop sections, lateral tracing of stratigraphic geometries, and correlation to a regional sequence stratigraphic–biostratigraphic framework form the basis of the interpretations.
The sequence stratigraphic evolution of the study area consists of a second-order, transgressive–regressive depositional sequence, composed of eight composite (third-order) depositional sequences and their constituent high-frequency (fourth-order) sequences. One lowest Famennian third-order sequence is briefly described. The composite sequences are correlated from the northwestern margin of the Southesk Cairn carbonate complex at Toma Creek to time-equivalent strata exposed in the Nikanassin Range. Exposures in the Nikanassin Range include a carbonate shelf prograding southeast into the South Jasper Basin.
Stratigraphic architecture of the carbonate platforms was influenced by relative sea-level change within the second-order sequence and timing of basin fill in the Jasper Basin. Extensive euxinic shale deposition occurred in the mid-Frasnian, with its maximum extent coinciding with the second-order Maximum Flooding Surface (MFS), in the Woodbend 2.3 high-frequency sequence. Stratigraphic architecture generally follows the second-order trend, but significant deviations from that trend are observed at both the composite and high-frequency sequence scale. Basinally restricted wedges of shallow-water carbonate occur above third- and fourth-order sequence boundaries during the second-order transgression.
Slowing relative sea-level rise in the second-order highstand was reinforced by third- and fourth-order relative falls to produce complex stratigraphic architecture at the platform margins. Offlapping strata with basinally restricted shelf margin deposits and falling stage geometries are uniquely well exposed in the Nikanassin Range, allowing detailed reconstruction of sea-level fluctuations in the second-order highstand. Restricted marine circulation onto the carbonate platforms and basin filling in the late Frasnian coincided with extensive siliciclastic silt deposition in the study area. Silt was deposited during third- and fourth-order lowstands, bypassed into the basin and was reworked during intermittent inundation of the carbonate platforms.