Microjointing in Basement, Middle Rocky Mountains of Montana and Wyoming

Research Article| April 01, 1964 Microjointing in Basement, Middle Rocky Mountains of Montana and Wyoming DONALD U WISE DONALD U WISE Franklin and Marshall College, Lancaster, Pa. Search for other works by this author on: GSW Google Scholar Author and Article Information DONALD U WISE Franklin and Marshall College, Lancaster, Pa. Publisher: Geological Society of America Received: 23 Feb 1961 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1964, 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 (1964) 75 (4): 287–306. https://doi.org/10.1130/0016-7606(1964)75[287:MIBMRM]2.0.CO;2 Article history Received: 23 Feb 1961 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 DONALD U WISE; Microjointing in Basement, Middle Rocky Mountains of Montana and Wyoming. GSA Bulletin 1964;; 75 (4): 287–306. doi: https://doi.org/10.1130/0016-7606(1964)75[287:MIBMRM]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 Microjoints, defined as four or more macroscopic subparallel fractures spaced closer than 3 mm, appear as pervasive fracture systems in about half the Precambrian basement outcrops of Montana and Wyoming. Six thousand five hundred orientation measurements of the microjoints indicate that the common local pattern is two nearly vertical, perpendicular sets. Persistent vertical orientation at most, but not all, mountain fronts which have undergone demonstrable Laramide rotation of basement indicates microjoints developed subsequent to the bulk of Laramide deformation. The microjoints are interpreted as expansion features in Laramide block mountains, created as the blocks were lifted free of the confines of the adjacent basin floors.Microjoint systems simulate the orientations of ordinary joints, of Precambrian dikelets, and of most planes of microscopic fluid inclusions but are independent in degree of development. In thin section the microjoints are represented by one class of very tiny fluid inclusions paralleling and locally reopening older planes of inclusions. The microscopic fluid inclusion planes are interpreted as a system of Precambrian weakness directions partially controlling the orientations of all subsequent fracture systems including Laramide microjoints.On a regional scale the microjoints have a number of recurring directions similar to Spencer's (1959) common joint directions in the Beartooth Mountains, Montana. Thus, the available measurements suggest a regional system of eight recurring fracture directions. 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.