Origin of a classic cratonic sheet sandstone: Stratigraphy across the Sauk II–Sauk III boundary in the Upper Mississippi Valley

Abstract

Research Article| February 01, 1998 Origin of a classic cratonic sheet sandstone: Stratigraphy across the Sauk II–Sauk III boundary in the Upper Mississippi Valley Anthony C. Runkel; Anthony C. Runkel 1Minnesota Geological Survey, 2642 University Avenue, St. Paul, Minnesota 55114-1057 Search for other works by this author on: GSW Google Scholar Robert M. McKay; Robert M. McKay 2Iowa Department of Natural Resources, Geological Survey Bureau, 109 Trowbridge Hall, Iowa City, Iowa 52242-1319 Search for other works by this author on: GSW Google Scholar Allison R. Palmer Allison R. Palmer 3Institute for Cambrian Studies, 445 North Cedarbrook Road, Boulder, Colorado 80304-0417 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1998) 110 (2): 188–210. https://doi.org/10.1130/0016-7606(1998)110<0188:OOACCS>2.3.CO;2 Article history first online: 01 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 Anthony C. Runkel, Robert M. McKay, Allison R. Palmer; Origin of a classic cratonic sheet sandstone: Stratigraphy across the Sauk II–Sauk III boundary in the Upper Mississippi Valley. GSA Bulletin 1998;; 110 (2): 188–210. doi: https://doi.org/10.1130/0016-7606(1998)110<0188:OOACCS>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 SocietyGSA Bulletin Search Advanced Search Abstract The origin of cratonic sheet sandstones of Proterozoic and early Paleozoic age has been a long-standing problem for sedimentologists. Lower Paleozoic strata in the Upper Mississippi Valley are best known for several such sandstone bodies, the regional depositional histories of which are poorly understood. We have combined outcrop and subsurface data from six states to place the Upper Cambrian Wonewoc (Ironton and Galesville) Sandstone in a well-constrained stratigraphic framework across thousands of square kilometers. This framework makes it possible for the first time to construct a regional-scale depositional model that explains the origin of this and other cratonic sheet sandstones.The Wonewoc Sandstone, although mapped as a single contiguous sheet, is a stratigraphically complex unit that was deposited during three distinct conditions of relative sea level that span parts of four trilobite zones. During a relative highstand of sea level in Crepicephalus Zone time, quartzose sandstone lithofacies aggraded more or less vertically in nearshore-marine and terrestrial environments across much of the present-day outcrop belt around the Wisconsin arch. At the same time, finer grained, feldspathic sandstone, siltstone, and shale aggraded in deeper water immediately seaward of the quartzose sand, and shale and carbonate sediment accumulated in the most distal areas. During Aphelaspis and Dunderbergia Zones time a relative fall in sea level led to the dispersal of quartzose sand into a basinward-tapering, sheet-like body across much of the Upper Mississippi Valley. During early Elvinia Zone time a major transgression led to deposition of a second sheet sandstone that is generally similar to the underlying regressive sheet.The results of this investigation also demonstrate how subtle sequence-bounding unconformities may be recognized in mature, cratonic siliciclastics. We place the Sauk II-Sauk III subsequence boundary at the base of the coarsest bed in the Wonewoc Sandstone, a lag developed through erosion that occurred during the regional regressive-transgressive event that spanned Aphelaspis to early Elvinia Zones time. Such sequence-bounding unconformities are difficult to recognize where they are contained within coarse siliciclastics of the Upper Mississippi Valley, because they separate strata that are texturally and mineralogically similar, and because erosion occurred on a loose, sandy substrate along a low, uniform gradient, and in a nonvegetated terrestrial environment. Furthermore, the ultramature mineral composition of the exposed substrate is resistant to the development of a recognizable weathering profile.The well-known sheet geometry of the Wonewoc and other units of lower Paleozoic sandstone of this area is not dependent on atypical terrestrial depositional conditions conducive to the widespread distribution of sand, as commonly believed. Sand was spread into a sheet dominantly within the marine realm in a manner similar to that inferred for many better-known sandstone bodies deposited in the North American Cretaceous Western Interior seaway and Tertiary Gulf of Mexico. The laterally extensive, thin character of the Upper Mississippi Valley sandstone bodies compared to these other sandstone bodies simply reflects deposition of a continuously abundant supply of sand on a relatively stable, nearly flat basin of slow, uniform subsidence during changes in sea level. The dearth of shale in this and other cratonic sandstones can be indirectly attributed to the same controls, which led to an uncommonly low preservation potential for fairweather deposits on the shoreface. 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.