The Sauk Megasequence from the Reelfoot Rift to Southwestern Missouri
Published:January 01, 2012
James Palmer, Thomas L. Thompson, Cheryl Seeger, James F. Miller, Jay M. Gregg, 2012. "The Sauk Megasequence from the Reelfoot Rift to Southwestern Missouri", 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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Middle Cambrian–Lower Ordovician (Sauk megasequence) rocks of southern Missouri have attracted interest because they host the large Mississippi Valley-type ore deposits of that region. A Proterozoic igneous and metamorphic complex nonconformably underlies this megasequence and Mississippian and Pennsylvanian strata unconformably overlay these units. Strata of the Sauk megasequence in southern Missouri include, in ascending order, the Cambrian Lamotte Sandstone, Bonneterre Dolomite, Davis Formation, Derby-Doerun Dolomite, Potosi Dolomite, and Eminence Dolomite, which are overlain by the Ordovician Gasconade Dolomite, Roubidoux Formation, Jefferson City Dolomite, and Cotter Dolomite.
Cambrian depositional facies in southern Missouri are small- to large-scale, unconformity-bounded, transgressive-regressive sequences, and are characterized by distinct facies in linear belts that developed on and adjacent to basement highs. These include intrashelf-basin facies distal from basement highs, platform-edge facies in narrow belts adjacent to highs, and back-reef facies proximal to and within the St. Francois Mountains. A distinct rift-graben facies is characteristic of deposition of these units in the Reelfoot rift. An epeiric sea that extended over the region controlled Lower Ordovician deposition. Lower Ordovician strata are com-posed of five third-order sequences, punctuatedbyregional and sub regional unconformities. The strata are characterized by facies that have regional lateral continuity.
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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.