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.
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NEWADVANCES IN DEVONIAN CARBONATES: OUTCROP ANALOGS, RESERVOIRS AND CHRONOSTRATIGRAPHY
The Devonian stratigraphic record contains a wealth of information that highlights the response of carbonate platforms to both global-scale and local phenomena that drive carbonate architecture and productivity. Signals embedded particularly in the Middle-Upper Devonian carbonate record related to biotic crises and stressed oceanic conditions, long-term accommodation trends, and peak greenhouse to transitional climatic changes are observed in multiple localities around the world and temporally constrained by biostratigraphy, highlighting distinct and impactful global controls. Devonian datasets also stress the importance of local or regional phenomena, such as bolide impacts, the effects of terrestrial input and paleogeography, syn-depositional tectonics, and high-frequency accommodation drivers, which add complexity to the carbonate stratigraphic record when superimposed on global trends. The unique occurrence of well-studied and pristinely preserved reefal carbonate outcrop and subsurface datasets, ranging across the globe from Australia to Canada, allows for a detailed examination of Devonian carbonate systems from a global perspective and the opportunity to develop well-constrained predictive relationships and conceptual models. Advances in the understanding of the Devonian carbonate system is advantageous considering, not only the classic conventional reservoirs such as the pinnacle reefs of the Alberta Basin, but also emerging conventional reservoirs in Eurasia, and many unconventional plays in North America. The papers in this volume provide updated stratigraphic frameworks for classic Devonian datasets using integrated correlation approaches; new or synthesized frameworks for less studied basins, reservoirs, or areas; and discussions on the complex interplay of extrinsic and intrinsic controls that drive carbonate architectures, productivity, and distribution. The 13 papers in this special publication include outcrop and subsurface studies of Middle to Upper Devonian carbonates of western Canada, the Lennard Shelf of the Canning Basin, Western Australia, and the western USA.