Giant Desiccation Polygons of Great Basin Playas

Abstract

Research Article| January 01, 1968 Giant Desiccation Polygons of Great Basin Playas JAMES T NEAL; JAMES T NEAL Terrestrial Sciences Laboratory, Air Force Cambridge Research Laboratories, Bedford, Massachusetts Search for other works by this author on: GSW Google Scholar ARTHUR M LANGER; ARTHUR M LANGER Department of Community Medicine, Mount Sinai Hospital, New York, New York Search for other works by this author on: GSW Google Scholar PAUL F KERR PAUL F KERR Department of Geology, Columbia University, New York, New York Search for other works by this author on: GSW Google Scholar GSA Bulletin (1968) 79 (1): 69–90. https://doi.org/10.1130/0016-7606(1968)79[69:GDPOGB]2.0.CO;2 Article history received: 07 Jul 1966 rev-recd: 05 Jan 1967 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation JAMES T NEAL, ARTHUR M LANGER, PAUL F KERR; Giant Desiccation Polygons of Great Basin Playas. GSA Bulletin 1968;; 79 (1): 69–90. doi: https://doi.org/10.1130/0016-7606(1968)79[69:GDPOGB]2.0.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 Several previous investigators have recognized giant polygonal fissure patterns in 6 playas of the Basin and Range Physiographic Province (Great Basin). This paper extends the study to 39 playas in Oregon, Nevada, California, Arizona, and New Mexico, with observations on the physical and mineralogical features of fissured and nonfissured areas.Fissures are often 5 m deep and the polygons may attain a width of 300 m. These giant mud cracks develop in clay playas and are attributed to desiccation phenomena. As dehydration proceeds from the surface downward and penetrates the capillary fringe above the water table, shrinkage occurs, which ultimately results in rupture at depth that extends upward to the surface.The mineral constituents of sediments in both the fissured and nonfissured areas are predominantly clay minerals, carbonates, salines, and analcite, with fine grains of quartz, feldspar, and ferro-magnesian silicates. Fissured playas possess significantly greater quantities of clay and carbonate minerals as compared to nonfissured playas. The clay minerals, carbonates, and analcite are primarily present in <2μ size fraction. This colloidal aggregate is believed to exert a major influence on the physical behavior of the sediments which contain the giant polygons. In particular, the dehydration to an almost dry condition of a clay mass, in which the water content may exceed the mineral content, results in a major loss of volume. The shrinkage leads to rupture with the formation of fissures. The fissures form orthogonal polygons characteristic of volume change in a largely uniform horizontal mass with one surface exposed. 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.