Description: The expansive soils hazard map layer displays the location of geologic formations with known or suspected occurrences of shrink-swell clays, which may lead to expansive soil development. The most common shrink-swell clays in Wyoming are sodium montmorillonite (also known as bentonite) and calcium montmorillonite. These clays are prevalent in Late Cretaceous shales and can occur locally in other formations. Sodium and calcium montmorillonite-bearing formations were extracted directly from the 1:500,000 scale Geologic Map of Wyoming (Love and Christiansen, 2014) to create the expansive soils hazard map. Expansive soil hazards are divided into two classes for the purpose of this map and associated dataset:Regionally susceptible, moderate hazardCretaceous shales described by Love and Christiansen (2014) to contain sodium and/or calcium montmorillonite and with well-documented occurrences of expansive soils. Montmorillonite minerals from these shales are prevalent enough to be mined and/or have historically caused expansive soil damage. These shales are susceptible to developing expansive soil issues on a regional scale.Locally susceptible, low hazardFormations, including Jurassic and Early Cretaceous shales and Paleogene volcaniclastic rocks, described by Love and Christiansen (2014) to contain sodium and/or calcium montmorillonite. Montmorillonite minerals from these geologic formations are not prevalent enough to mine and there is limited documentation of clays from these formations causing infrastructure damage. These formations have a potential to develop expansive soils issues in localized areas.This data set was updated in 2014 by the Wyoming State Geological Survey. Polygons were merged, description information was completed, and geologic units were converted to representations to retain unit colors and patterns.The geologic map was digitized by Green, G.N., and Drouillard, P.H., 1994, from original scribe sheets used to prepare the published 1:500,000-scale Geologic Map of Wyoming (Love and Christiansen, 1985). Stable base contact prints of the scribe sheets were scanned on a Tektronix 4991 digital scanner. The scanner automatically converts the scanned image to an ASCII vector format. These vectors were transferred to a VAX minicomputer, where they were loaded into Arc/Info. The dataset includes both linear and polygon features, with attributes derived from the original 1985 map. Original images (Map, Legend, and Sources): http://www.uwyo.edu/geolgeophys/about/geologic-map-wyoming.htmlUpdated data set available for download through the WSGS web site: www.wsgs.wyo.gov/ or WyGISC GeoLibrary : http://wygl.wygisc.org/wygeolib/catalog/main/home.pageDIGITAL DATA INFORMATION:GEOLOGIC SYMBOLOGY (FGDCGeoAge font used for labeling Special Characters in SYMBOL field):Mz = MesozoicPz = PaleozoicK = Cretaceous^ = TriassicIP = Pennsylvanian_ = Cambrian< = ProterozoicY = Middle ProterozoicX = Early ProterozoicW = Late ArcheanV = Middle ArcheanU = Early ArcheanFOOTNOTES (fn):1. Query indicates uncertainty of position of top of unit within the Pleistocene.2. Age of upper parts of uppermost Miocene units is problematic. These parts have historically been assigned to the Pliocene. Successive reductions in radiometric age of the top of the Miocene in Europe to 7 Ma (Lambert, 1971) and to 5 Ma (Berggren, 1972) place a Pliocene age in question, although the top beds of the formations have not been dated.3. Karlstrom and others (1983).4. Divis (1976).5. Houston and others (1968).6. Snyder (1980).7. McCallum (1968).
Service Item Id: 9806a063b3694020ba65bd8c3a8af50e
Copyright Text: WSGS update in 2014. Gregory N. Green, and Patricia H. Drouillard, 1994, digitized the Geologic Map of Wyoming. Original scribe sheets and negatives were from David Love, Anne Coe Christiansen. Pat Stamile of the USGS and Chris Arneson and Laisan Serebryakov of the University of Wyoming Water Resources Center provided digital review. Original Geologic Map of Wyoming, Love and Christiansen, 1985.