Alteration of early-formed dolomite during shallow to deep burial: Mississippian Mission Canyon Formation, central to southwestern Montana

Research Article| November 01, 1993 Alteration of early-formed dolomite during shallow to deep burial: Mississippian Mission Canyon Formation, central to southwestern Montana TAD M. SMITH; TAD M. SMITH 1Department of Geology, Texas A&M University, College Station, Texas 77843 Search for other works by this author on: GSW Google Scholar STEVEN L. DOROBEK STEVEN L. DOROBEK 1Department of Geology, Texas A&M University, College Station, Texas 77843 Search for other works by this author on: GSW Google Scholar Author and Article Information TAD M. SMITH 1Department of Geology, Texas A&M University, College Station, Texas 77843 STEVEN L. DOROBEK 1Department of Geology, Texas A&M University, College Station, Texas 77843 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1993) 105 (11): 1389–1399. https://doi.org/10.1130/0016-7606(1993)105<1389:AOEFDD>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 Email Permissions Search Site Citation TAD M. SMITH, STEVEN L. DOROBEK; Alteration of early-formed dolomite during shallow to deep burial: Mississippian Mission Canyon Formation, central to southwestern Montana. GSA Bulletin 1993;; 105 (11): 1389–1399. doi: https://doi.org/10.1130/0016-7606(1993)105<1389:AOEFDD>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 Dolomite in the Mississippian Mission Canyon Formation (Osagean to middle Meramecian) of central and southwestern Montana precipitated during multiple episodes of dolomitization and/or recrystallization. The earliest generation of dolomite most likely precipitated from evaporated sea water in near-surface diagenetic environments when the Mission Canyon platform intermittently aggraded to sea level. This dolomite has relatively positive δ18O values (-1.5‰ to +7.5‰) and typically is nonstoichiometric and trace-element enriched. A second generation of dolomite has very negative δ18O values (-11.2‰ to - 1.5‰) and always is stoichiometric and trace-element depleted. Dolomite with δ18O values <-6.8‰ is in the upper 100-180 m of the Mission Canyon Formation, beneath a regional post-Mission Canyon unconformity and karst surface that extends across the entire study area. Dolomite depleted in 18O may have (1) precipitated initially in a regional mixing zone during post-Mission Canyon subaerial exposure and karstification, (2) precipitated at elevated temperatures during later diagenesis, or (3) recrystallized from an earlier generation of dolomite during later shallow to deep burial diagenesis. Very negative δ18O values and low trace-element contents for the second generation of dolomite suggest that diagenetic solutions were dominated by meteoric water, whereas δ13C values indicate that diagenetic fluids were buffered by Osagean carbonate rocks. The Mission Canyon Formation is similar to many carbonate sequences in that multiple episodes of dolomitization may be responsible for the eventual stratigraphic distribution of dolomite and its petrographic and geochemical characteristics. 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.