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LaHood Formation—A Coarse Facies of the Belt Series in Southwestern Montana

1963; Geological Society of America; Volume: 74; Issue: 4 Linguagem: Inglês

10.1130/0016-7606(1963)74[407

1943-2674

William J. McMannis,

Geological formations and processes

Research Article| April 01, 1963 LaHood Formation—A Coarse Facies of the Belt Series in Southwestern Montana WILLIAM J McMANNIS WILLIAM J McMANNIS Montana State College, Bozeman, Montana Search for other works by this author on: GSW Google Scholar Author and Article Information WILLIAM J McMANNIS Montana State College, Bozeman, Montana Publisher: Geological Society of America Received: 29 Jan 1962 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1963, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1963) 74 (4): 407–436. https://doi.org/10.1130/0016-7606(1963)74[407:LFCFOT]2.0.CO;2 Article history Received: 29 Jan 1962 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation WILLIAM J McMANNIS; LaHood Formation—A Coarse Facies of the Belt Series in Southwestern Montana. GSA Bulletin 1963;; 74 (4): 407–436. doi: https://doi.org/10.1130/0016-7606(1963)74[407:LFCFOT]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 Precambrian arkose and arkose conglomerate that contrast sharply with the commonly fine-grained units of the Belt Series crop out in a narrow zone from the Bridger Range on the east to the Highland Mountains on the west in southwestern Montana. The name LaHood Formation is satisfactory for these beds, but the formation is clarified and redefined, and a principal reference section is introduced to indicate more complete, more accessible exposures. The names North Boulder Group and East Gallatin Group should be abandoned.The LaHood represents a long time-stratigraphic interval. Its intertonguing relationships with typical fine-grained Belt formations, and data regarding pre-Flathead (Middle Cambrian) truncation of Belt strata, permit correlations that show that LaHood equivalents range from oldest known Belt up to mid-Greyson. These correlations suggest relationships between rocks of the Philipsburg district and the type Belt that are quite different from those of other authors.The LaHood formed in a partly fault-controlled eastward embayment of the Belt geosyncline. The detritus was derived from a rugged source area of older Precambrian metamorphic rocks to the south. It was dumped by torrential streams into the differentially subsiding marginal part of the Belt sea and was redistributed to more stable bottom areas by slumping and turbidity currents.Sedimentary characteristics, regional truncation and local angular unconformities beneath the Flat-head Quartzite indicate regional northward tilting, broad folding, and faulting during and after deposition of Belt sediments but before the Flathead Quartzite formed. 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.