"The Gasconade Formation (Lower Ordovician) has been studied in the surface and subsurface in the Ozarks of Missouri and northeastern Oklahoma. The formation is mostly dolomite with a sandstone member at the base (Gunter) and frequent occurrences of chert bodies of different shapes particularly in the middle part.
The dolomite crystals in the lower and upper parts are subhedral to euhedral of equicrystalline to two-size fabric and range in size from 300-600 microns, and subhedral to anhedral of variable fabric and smaller size in the middle part. A sequence of cloudy and clear areas, named zoning, characterizes the euhedral crystals. Three different types of zoning are recognized; type A, cloudy interior-clear rims; type B, clear interior-cloudy rims and type C, a combination of both or repetition of either, the latter being the most common. Pellets, oolites, intraclasts, fossils, and algal (cryptozoan) structures characterize the formation especially the middle part. The Gunter sandstone is bimodal to polymodal.
Post-dolomitization solution affected the dolomite and sandstone of the formation causing stylolites, rim and center corrosion, secondary mineral growth and pyrite replacement in dolomite and quartz.
Both the dolomite and chert in the Gasconade Formation have been formed by replacement. Dolomite replacement occurred in three phases, early, middle (main) and late. Over 90 percent of the original carbonate has been dolomitized during the main phase of dolomitization. Chert replacement occurred in two phases, early and late. The early phase of chertification either interrupted or occurred soon after the main phase of dolomitization.
The Gasconade Formation was deposited in the intertidal zone of a shallow sea. During the deposition of the middle part of the formation, the sea was shallower than during the deposition of either the lower or the upper parts.
The diagenesis of the formation follows the following sequence: early phase of dolomitization; middle (main) phase of dolomitization; early phase of chertification; late phase of chertification and late phase of dolomitization"--Abstract, pages ii-iii.
Spreng, Alfred C., 1923-2012
Beveridge, Thomas R. (Thomas Robinson), 1918-1978
Grant, S. Kerry
Wilson, Tommie C., 1939-
Geosciences and Geological and Petroleum Engineering
Ph. D. in Geology
V. H. McNutt Memorial Foundation
Cultural and Educational Bureau of the Arab Republic of Egypt in Washington
University of Missouri--Rolla
xii, 182 pages
© 1973 Abd El-Aziz Ei-Hady Ahmad Borahay, All rights reserved.
Dissertation - Open Access
Geology, Stratigraphic -- Ordovician
Geology -- Missouri
Petrology -- Missouri
Diagenesis -- Missouri
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Borahay, Abd El-Aziz El-Hady A., "Petrography, diagenesis and environment of deposition of the Gasconade Formation, Lower Ordovician, southern Missouri" (1973). Doctoral Dissertations. 228.