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Diagenesis of Fossiliferous Concretions from the Upper Cretaceous Fox Hills Formation, North Dakota

1988; Society for Sedimentary Geology; Volume: Vol. 58; Linguagem: Inglês

10.1306/212f8e27-2b24-11d7-8648000102c1865d

1938-3681

Scott J. Carpenter, Jd Erickson, Kyger C. Lohmann, Michael R. Owen,

Hydrocarbon exploration and reservoir analysis

Other| July 01, 1988 Diagenesis of fossiliferous concretions from the Upper Cretaceous Fox Hills Formation, North Dakota Scott J. Carpenter; Scott J. Carpenter Univ. Mich., Dep. Geol. Sci., Ann Arbor, MI, United States Search for other works by this author on: GSW Google Scholar J. Mark Erickson; J. Mark Erickson Search for other works by this author on: GSW Google Scholar Kyger C. Lohmann; Kyger C. Lohmann Search for other works by this author on: GSW Google Scholar Michael R. Owen Michael R. Owen Search for other works by this author on: GSW Google Scholar Author and Article Information Scott J. Carpenter Univ. Mich., Dep. Geol. Sci., Ann Arbor, MI, United States J. Mark Erickson Kyger C. Lohmann Michael R. Owen Publisher: SEPM Society for Sedimentary Geology First Online: 03 Mar 2017 Online ISSN: 1938-3681 Print ISSN: 1527-1404 GeoRef, Copyright 2006, American Geological Institute. Journal of Sedimentary Research (1988) 58 (4): 706–723. https://doi.org/10.1306/212F8E27-2B24-11D7-8648000102C1865D Article history First Online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Scott J. Carpenter, J. Mark Erickson, Kyger C. Lohmann, Michael R. Owen; Diagenesis of fossiliferous concretions from the Upper Cretaceous Fox Hills Formation, North Dakota. Journal of Sedimentary Research 1988;; 58 (4): 706–723. doi: https://doi.org/10.1306/212F8E27-2B24-11D7-8648000102C1865D 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 SocietyJournal of Sedimentary Research Search Advanced Search Abstract Three fossiliferous concretions of the Fox Hills Formation (Upper Cretaceous) of North Dakota display similar diagenetic histories. Petrographic and geochemical data from each concretion have yielded the following diagenetic sequence: 1) bioturbation by marine benthos; 2) partial phosphatization of glauconite, fecal pellets, and shell material; 3) sulfate reduction and pyrite formation; 4) siderite precipitation; 5) radial-fibrous calcite precipitation, and 6) equant calcite precipitation. Although the occurrence of open-marine faunas and glauconite indicates that concretion sediments were deposited under marine conditions, geochemical data suggest that marine pore fluids were replaced by brackish and meteoric water. As the Fox Hills Formation is part of a regressive, marginal marine sequence, it is likely that the transition from marine to freshwater is recorded in concretion paragenesis. Early diagenetic minerals indicate oxidation of organic matter at shallow burial depths under normal marine conditions. Locally reducing conditions, produced initially by degradation of molluscan soft parts and later by degradation of organic material in crustacean and annelid fecal pellets, occurred at shallow burial depths. Alteration of iron silicates (glauconite) produced pore fluids enriched in Fe (super 2+) . Due to the abundance of reactive organic matter, subsequent reduction of marine sulfate yielded a small amount of disseminated pyrite. Following the removal of H 2 S, elevated Fe (super 2+) , pH, and bicarbonate concentrations soon exceeded siderite saturation and siderite was precipitated. Elevated Ca and Mg compositions and marine delta 18 O values of siderite cements indicate that pore fluids were essentially reduced marine fluids. Depleted delta 13 C values suggest that siderite precipitated in an environment dominated by the oxidation of organic matter. Isotopic compositions from the earliest and latest carbonate phases constrain intermediate phases and allow comparison of environments of precipitation. Carbon and oxygen isotopic data from skeletal aragonite provide an estimate of the isotopic composition of marine carbonate. The latest phase of equant calcite cement is characterized by invariant delta 18 O, coupled with highly variable and light delta 13 C. This characteristic isotopic signature and occurrence in overlying fluvial sediments suggests a meteoricphreatic origin for equant spars. Isotopic values of radial-fibrous calcite lie between those of marine (aragonite, siderite) and freshwater (equant calcite) phases and represent a complex mixing of marine and meteoric pore fluids. The paragenetic sequence of carbonate cements records a gradual decrease in ambient fluid Mg, Fe, and Mn content during shallow burial. Such decreases are consistent with the influx of oxidizing meteoric fluids. 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.