Episodic potassic diagenesis of Ordovician tuffs in the Mississippi Valley area

Research Article| August 01, 1988 Episodic potassic diagenesis of Ordovician tuffs in the Mississippi Valley area R.L. Hay; R.L. Hay 1Department of Geology, University of Illinois, 1301 West Green Street, Urbana, Illinois 61801 Search for other works by this author on: GSW Google Scholar Mingchou Lee; Mingchou Lee 2Department of Geological Sciences, Case Western Reserve University, Cleveland, Ohio 44106 Search for other works by this author on: GSW Google Scholar Dennis R. Kolata; Dennis R. Kolata 3Illinois State Geological Survey, 615 East Peabody Drive, Champaign, Illinois 61820 Search for other works by this author on: GSW Google Scholar J. C. Matthews; J. C. Matthews 1Department of Geology, University of Illinois, 1301 West Green Street, Urbana, Illinois 61801 Search for other works by this author on: GSW Google Scholar J. P. Morton J. P. Morton 2Department of Geological Sciences, Case Western Reserve University, Cleveland, Ohio 44106 Search for other works by this author on: GSW Google Scholar Geology (1988) 16 (8): 743–747. https://doi.org/10.1130/0091-7613(1988)016<0743:EPDOOT>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation R.L. Hay, Mingchou Lee, Dennis R. Kolata, J. C. Matthews, J. P. Morton; Episodic potassic diagenesis of Ordovician tuffs in the Mississippi Valley area. Geology 1988;; 16 (8): 743–747. doi: https://doi.org/10.1130/0091-7613(1988)016<0743:EPDOOT>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Cambrian-Ordovician strata of the Mississippi Valley have been extensively modified by potassic diagenesis. Ordovician vitric tuffs are altered to K-feldspar and illite-rich, mixed-layer illite-smectite (I/S), both of which have been dated by K/Ar. Rb/Sr dates for K-feldspar support its reliability as a K/Ar clock, despite a dislocation density of 109-1010 cm-2. Age data document three Paleozoic episodes of potassic diagenetis, which have mean ages of 396 Ma (Early Devonian) for K-feldspar of the upper Mississippi Valley (UMV), 362 Ma (Late Devonian) for I/S off the UMV, and 265 Ma (Permian) for I/S of Missouri.Devonian dates from the UMV correspond to times of wide-spread epeirogeny in the U.S. midcontinent, and diagenetic episodes are attributed to regional flow of basinal brines caused by ground water recharge on uplifted arches. Potassium for K-feldspar may have come from the Michigan basin, and K for illite may have come from the east-central Iowa basin. K-feldspar and I/S of the UMV are in oxygen-isotopic disequilibrium, indicating that the K-feldspar crystallized from fluid that was either warmer or had lower δ18O values than that of the I/S. Permian illitization apparently records northward movement of warm saline fluid as a result of the Ouachita orogeny. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.