The Sauk-Tippecanoe Megasequence Boundary in an Interior Structural Corridor (Ottawa Embayment) of the Great American Carbonate Bank
George R. Dix, 2012. "The Sauk-Tippecanoe Megasequence Boundary in an Interior Structural Corridor (Ottawa Embayment) of the Great American Carbonate Bank", 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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The Ottawa embayment forms an approximately 200-km (∼125-mi) structural indentation along the strike of the Precambrian Grenville province in central Canada. It follows the trace of a Neoproterozoic fault system that was reactivated episodically during the Phanerozoic. The Potsdam and Beekmantown Groups comprise the local Sauk megasequence. The former consists of a Neoproterozoic to Cambrian disconformable transition from immature feldspathic to very mature quartz arenites, culminating in restricted marine depositional conditions. The Beekmantown Group overlies the older succession with disconformity, and its lower and middle formations record a net onlap of increasingly deeper paleoenvironmental conditions; from peritidal (Theresa Formation) to shelfal (Beauharnois Formation) sandstone and dolostone facies, within a developing narrow seaway. The youngest formation, the Carillon Formation, consists of poorly fossiliferous seismite-bearing dolomudstone and abundant shale that abruptly onlap locally karstified and faulted Beauharnois strata. The Carillon Formation is early Middle Ordovician in age, post-Rangerian, but not younger than the Histiodella holodentata conodont Biozone. The formation contains abundant evidence of synsedimentary tectonisn that was coincident with far-field (>1000 km [>620 mi]) events along the St. Lawrence promontory, where uplift and deformation produced a prominent Sauk-Tippecanoe megasequence disconformity. Notable differences exist in the Middle Ordovician sea level record within the embayment compared with that along the Laurentian shelf margin, with deposition and synde-positional tectonism spanning formation of the outer-shelf Sauk-Tippecanoe megasequence boundary. A stratigraphic interval, the Carillon Formation, defines the Sauk-Tippecanoe transition within this interior structural corridor of the great American carbonate bank.
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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.