Sauk Megasequence Deposition in Northeastern Washington, Northern Idaho, and Western Montana
John H. Bush, Robert C. Thomas, Michael C. Pope, 2012. "Sauk Megasequence Deposition in Northeastern Washington, Northern Idaho, and Western Montana", 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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Lower Cambrian–Lower Ordovician passive-margin sediments were deposited across northeastern Washington, northern Idaho, and western Montana. Lower Cambrian strata record the initial transgression onto Laurentia in northeastern Washington. Middle Cambrian–Lower Ordovician units were deposited across a much broader area and record the establishment of a western ooid-algal shoal complex that restricted water circulation in an intrashelf basin that formed between the shoal and craton. Long-standing topographic highs in the region include Montania, which may have controlled the location of the ooid-algal shoal complex, and the Lemhi arch, which served as a western source area for siliciclastic sediment input. The Sauk megasequence sediments were deposited in multiple grand cycles that are regionally correlative. Each grand cycle consists of a shale and sandstone base deposited as sea level transgressed onto the craton. The basal siliciclastic units are gradationally overlain by carbonate, which was deposited as sea level continued to rise and an extensive carbonate platform developed. Some of the boundaries between the grand cycles are unconformities, recording rapid changes in sea level. Meter-scale shallowing-upward cycles are common within grand cycles, but they have not yet been regionally correlated.
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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.