Eustatic control on early dolomitization of cyclic peritidal carbonates: Evidence from the Early Ordovician Upper Knox Group, Appalachians

Abstract

Research Article| July 01, 1992 Eustatic control on early dolomitization of cyclic peritidal carbonates: Evidence from the Early Ordovician Upper Knox Group, Appalachians ISABEL P. MONTAÑEZ; ISABEL P. MONTAÑEZ 1Department of Earth Sciences, University of California, Riverside, California 92521 Search for other works by this author on: GSW Google Scholar J. FRED READ J. FRED READ 2Department of Geological Sciences, Virginia Polytechnic Institute, Blacksburg, Virginia 24061 Search for other works by this author on: GSW Google Scholar Author and Article Information ISABEL P. MONTAÑEZ 1Department of Earth Sciences, University of California, Riverside, California 92521 J. FRED READ 2Department of Geological Sciences, Virginia Polytechnic Institute, Blacksburg, Virginia 24061 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1992) 104 (7): 872–886. https://doi.org/10.1130/0016-7606(1992)104<0872:ECOEDO>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 MailTo Tools Icon Tools Get Permissions Search Site Citation ISABEL P. MONTAÑEZ, J. FRED READ; Eustatic control on early dolomitization of cyclic peritidal carbonates: Evidence from the Early Ordovician Upper Knox Group, Appalachians. GSA Bulletin 1992;; 104 (7): 872–886. doi: https://doi.org/10.1130/0016-7606(1992)104<0872:ECOEDO>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 The Early Ordovician Upper Knox Group is characterized by stacked meter-scale peritidal cycles that repeat at high frequencies (104 to 105 yr). Stacking patterns (stratigraphic trends in lithofacies and cycle thickness) of meter-scale cycles define five depositional sequences that, in conjunction with Fischer plots, delineate five long-term relative sea-level fluctuations during Upper Knox deposition. Intrabasinal and interbasinal correlation of Upper Knox Fischer plots suggests that the third-order sea-level events were eustatic. Meter-scale peritidal cycles likely formed in response to high-frequency, fourth-and fifth-order, eustatic sea-level fluctuations superimposed on these third-order sea-level events.Upper Knox cyclic carbonates are extensively dolomitized; as much as 85% of all dolomite is stratiform and consists of early dolomite exhibiting minor to extensive modification by burial dolomite. Synsedimentary dolomitization likely occurred in modified sea water during tidal-flat progradation governed by high-frequency sea-level events. This is suggested by the common association of dolomite with mud-cracked laminites and silicified evaporite nodules, the systematic decrease in dolomite abundance below laminite cycle caps, and the presence of dolomite clasts in regoliths veneering high-frequency cycle tops or in transgressive limestones of the overlying cycle. Dolomite distribution within depositional sequences shows a strong relationship to third- and fourth-order eustatic sea-level events, indicating that long-term eustasy also strongly controlled early dolomitization of Upper Knox carbonates.Mass-balance calculations show that the proposed sabkha model of dolomitization in concert with composite eustasy could generate stratiform dolomite of considerable vertical and lateral extent in peritidal cyclic carbonates. This reflects the duration of progradation and supratidal exposure (104 to 105 yr) available for dolomitization to proceed, and the broad zone of active dolomitization that would develop during continued progradation throughout each cycle period. 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.