Delle Phosphatic Member: An anomalous phosphatic interval in the Mississippian (Osagean-Meramecian) shelf sequence of central Utah

Abstract

Research Article| January 01, 1990 Delle Phosphatic Member: An anomalous phosphatic interval in the Mississippian (Osagean-Meramecian) shelf sequence of central Utah K. M. Nichols; K. M. Nichols 1U.S. Geological Survey, Federal Center, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar N. J. Silberling N. J. Silberling 1U.S. Geological Survey, Federal Center, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar Author and Article Information K. M. Nichols 1U.S. Geological Survey, Federal Center, Denver, Colorado 80225 N. J. Silberling 1U.S. Geological Survey, Federal Center, Denver, Colorado 80225 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1990) 18 (1): 46–49. https://doi.org/10.1130/0091-7613(1990)018<0046:DPMAAP>2.3.CO;2 Article history First Online: 02 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 K. M. Nichols, N. J. Silberling; Delle Phosphatic Member: An anomalous phosphatic interval in the Mississippian (Osagean-Meramecian) shelf sequence of central Utah. Geology 1990;; 18 (1): 46–49. doi: https://doi.org/10.1130/0091-7613(1990)018<0046:DPMAAP>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 SocietyGeology Search Advanced Search Abstract Phosphatic rocks are a distinctive part of the Lower and lower Upper Mississippian Delle Phosphatic Member of the Woodman Formation at the type locality of the member in the Lakeside Mountains, northwestern Utah. There, as elsewhere in central and western Utah, the Delle is composed of a relatively thin, anomalous depositional interval characterized by phosphorite, siliceous microfossils, secondary chert, distinctive dense lime mudstone, and argillaceous rocks stratigraphically sandwiched within a thick sequence of subtidal and peritidal Mississippian shelf carbonate and craton-derived siliciclastic rocks. Strongly reducing in-sediment conditions evidently prevailed at the onset of Delle deposition, yet sedimentologic features in the Delle such as endolithic-algal borings in pisolitic phosphorite and features in the rocks above and below the Delle such as tidally laminated fecal-pellet limestones and exclusively tractional sedimentary structures indicate shallow, shelf depositional environments. These rocks do not support the concept of a deep, sediment-starved depositional basin, the "Deseret deep starved basin" of previous authors. Rather, the nature of the Delle suggests incursion far onto the broad Early Mississippian shelf of nutrient-rich, organically productive waters possibly produced by upwelling in the coeval Antler foreland trough in central Nevada. This interpretation places the Early Mississippian shelf margin to the west of the Lakeside Mountains—probably west of Utah—rather than in central Utah, as required by the "Deseret deep starved basin" model. 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.