SEQUENCE STRATIGRAPHIC FRAMEWORK AND FACIES MODELS FOR THE LATE DEVONIAN TO EARLY MISSISSIPPIAN SAPPINGTON FORMATION (BAKKEN EQUIVALENT), SOUTHWEST MONTANA
Aaron P. Rodriguez, George W. Grader, John C. Hohman, P. Ted Doughty, John Guthrie, Peter E. Isaacson, 2017. "SEQUENCE STRATIGRAPHIC FRAMEWORK AND FACIES MODELS FOR THE LATE DEVONIAN TO EARLY MISSISSIPPIAN SAPPINGTON FORMATION (BAKKEN EQUIVALENT), SOUTHWEST MONTANA", NEWADVANCES IN DEVONIAN CARBONATES: OUTCROP ANALOGS, RESERVOIRS AND CHRONOSTRATIGRAPHY, Ted E. Playton, Charles Kerans, John A.W. Weissenberger
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The Sappington Formation is a Late Devonian to Early Mississippian age, primarily siliciclastic, formation that outcrops in southwestern Montana. The Sappington Formation has been presented in the past as broadly analogous in lithologic character and age to other formations in the region, the Bakken and Exshaw Formations. The Sappington Formation was the focus of several studies in the 1950s through 1970s that extensively analyzed the fauna and distribution of the formation and established a lithostratigraphic and biostratigraphic framework. This study provides a needed present day look at the Sappington Formation, by incorporating extensive previous work with present day field observations and modern geologic concepts. The methodology applied to this work includes literature review, outcrop observations, and interpretations on lithofacies, depositional environments, and sequence stratigraphy. Results from this work include a sequence stratigraphic model, depositional models, and a summary of the effects of allocylic processes on deposition. Three sequences were identified using previous biostratigraphy and correlated throughout the study area using lithostratigraphy. Recently, intracratonic Late Devonian and Early Mississippian age formations have become of economic importance as “unconventional” hydrocarbon plays, owing to success in the Bakken Formation.
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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.