Sauk Megasequence Supersequences, Southern Great Basin: Second-order Accommodation Events on the Southwestern Cordilleran Margin Platform
Martin Keller, Oliver Lehnert, John D. Cooper, 2012. "Sauk Megasequence Supersequences, Southern Great Basin: Second-order Accommodation Events on the Southwestern Cordilleran Margin Platform", Great American Carbonate Bank: The Geology and Economic Resources of the Cambrian—Ordovician Sauk Megasequence of Laurentia, James Derby, Richard Fritz, Susan Longacre, William Morgan, Charles Sternbach
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Compared to its type cratonal counterpart, the Sauk megasequence in the off-craton southern Great Basin is more fully developed and neatly packaged internally by regional unconformities. The Nopah Range in eastern California superbly and strategically exposes an exemplary and critical baseline Sauk section about 3000-m (∼9840-ft)-thick that provides an anchor for regional correlation. Beginning at the base of the Lower Cambrian middle member of the Wood Canyon Formation and terminating at the top of the upper Middle Or-dovician Eureka Quartzite, the Sauk megasequence can be subdivided physically into five supersequences based on sequence-stratigraphic criteria. Prominent platformwide emergence and erosion events, indicated by unconformities, and succeeding submergence and marine flooding events, recorded by overlying fine siliciclastic packages, coincide with contacts of the traditional lithostratigraphic framework. The five supersequences (Sauk-α, β, γ, δ, and ε) and their bounding unconformities reflect the major accommodation events across the platform of the southwestern Cordilleran margin and provide a chronostratigraphic framework guided by, but not dependent on, biostratigraphy. Within this framework, the Las Vegas branch of the great American carbonate bank system, which became established during a Middle Cambrian sea level highstand, rebounded impressively from platformwide interruptions by two supersequence boundary emergence and submergence events, only to meet its final fate from smothering by the voluminous Eureka quartz sand incursion.
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Great American Carbonate Bank: The Geology and Economic Resources of the Cambrian—Ordovician Sauk Megasequence of Laurentia
The Great American Carbonate Bank (GACB) comprises the carbonates (and related siliciclastics) of the Sauk megasequence, which were deposited on and around the Laurentian continent during Cambrian through earliest Middle Ordovician, forming one of the largest carbonate-dominated platforms of the Phanerozoic. The Sauk megasequence, which ranges upwards of several thousand meters thick along the Bank's margin, consists of distinctive Lithofacies and fauna that are widely recognized throughout Laurentia. A refined biostratigraphic zonation forms the chronostratigraphic framework for correlating disparate outcrops and subsurface data, providing the basis for interpreting depositional patterns and the evolution of the Bank. GACB hydrocarbon fields have produced 4 BBO and 21 TCFG, mostly from reservoirs near the Sauk-Tippecanoe unconformity. The GACB is also a source of economic minerals and construction material and, locally, serves as either an aquifer or repository for injection of waste material. This Memoir comprises works on biostratigraphy, ichnology, stratigraphy, depositional facies, diagenesis, and petroleum and mineral resources of the GACB. It is dedicated to James Lee Wilson who first conceived of this publication and who worked on many aspects of the GACB during his long and illustrious career.