Significance of Supratidal Dolomitization in the Geologic Record

Abstract

Research Article| January 01, 1972 Significance of Supratidal Dolomitization in the Geologic Record DONALD H ZENGER DONALD H ZENGER Geology Department, Pomona College, Claremont, California 91711 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1972) 83 (1): 1–12. https://doi.org/10.1130/0016-7606(1972)83[1:SOSDIT]2.0.CO;2 Article history received: 02 Apr 1971 rev-recd: 06 Jul 1971 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 H ZENGER; Significance of Supratidal Dolomitization in the Geologic Record. GSA Bulletin 1972;; 83 (1): 1–12. doi: https://doi.org/10.1130/0016-7606(1972)83[1:SOSDIT]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 Numerous discoveries of Holocene penecon-temporaneous dolomite forming mainly in the supratidal zone have prompted environmental analogies with ancient dolomites. Although most of these may be justified, overgeneralization has resulted. Many dolomites lack definitive evidence of either supratidal accumulation or supratidal dolomitization.Detailed field and laboratory studies of three dolomitic units in New York (Little Falls, Upper Cambrian; Herkimer, Middle Silurian; and Lockport, Middle Silurian) and one in California (Lost Burro, Middle and Upper Devonian) show that the dolomite, apparently metasomatic, represents original calcium carbonate sediments of variable environmental deposition. Portions of the Little Falls and Upper Lockport Formations contain evidence (algal stromatolites, desiccation cracks, intraclasts) of tidal flat (peritidal) deposition, whereas the other occurrences (Herkimer, Lost Burro, and lower Lockport) contain evidence (bioherms, abundant open-marine fossils) of subtidal accumulation. Dolomitization is primarily diagenetic. Even in those cases which possibly represent supratidal dolomitization, the dolomite is ordered and of much coarser grain size than that in the modern analogues.There is considerable evidence that much Holocene dolomite, as well as a substantial part of the dolomite in the geologic record, formed under evaporitic conditions, especially in contact with brines of high Mg++/Ca++ ratios. However, findings in Holocene sediments as well as the lack of indication of the initial presence of evaporites in many ancient dolomites suggest that dolomite need not be an evaporitic mineral. 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.