Organic matter accumulation,redox, and diagenetic history of the Marcellus Formation,southwestern Pennsylvania,Appalachian basin |
| |
| Institution: | 1. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China;2. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China;3. Department of Geology, University of Cincinnati, Cincinnati, OH 45221-0013, USA;1. Institut des sciences de la Terre, Université de Lausanne, Bâtiment Géopolis, CH-1015 Lausanne, Switzerland;2. Institut des sciences de la mer de Rimouski, Université du Québec à Rimouski, 310 allée des Ursulines, Rimouski, Quebec G5L 3A1, Canada;3. Geotop Research Centre, Université du Québec à Montréal, Montréal, Quebec H3C 3P8, Canada;4. Institut des dynamiques de la surface terrestre, Université de Lausanne, Bâtiment Géopolis, CH-1015 Lausanne, Switzerland;5. Laboratoire Géosystèmes, UMR-8217, Université Lille 1, CNRS, Villeneuve d’Ascq, France;6. UMR CNRS 5276 LGLTPE, Université Lyon 1, Campus de la Doua, Bâtiment Géode, F-69622 Villeurbanne Cedex, France;1. Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA;2. Department of Geology, University of Cincinnati, Cincinnati, OH 45221-0013, USA;3. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan, Hubei 430074, PR China;4. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, Hubei 430074, PR China;5. Department of Earth Science, East China Institute of Technology, Nanchang, Jiangxi 330013, PR China;6. GETECH, Kitson House, Elmete Hall, Elmete Lane, Leeds LS8 2LJ, United Kingdom;7. School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA |
| |
| Abstract: | Variations in the concentration of redox sensitive elements combined with pyrite framboid size data documented from a Marcellus Formation (Middle Devonian) core recovered from southwestern Pennsylvania elucidate the redox, organic matter accumulation, and diagenetic history of these deposits in this region of the basin. Uranium and Mo enrichment and Fe/Al display sharp increases coincident with diminishing Th/U upward through the initial 3rd order trangressive systems tract (lower Union Springs Member). These data as well as abundant small (<6 μm) pyrite framboids record establishment of strongly reducing benthic conditions, perhaps related to the expansion of an oxygen minimum zone induced by increased surface productivity. Strongly anoxic, even euxinic, conditions were interrupted by episodes of dysoxia, perhaps seasonal or longer term. Overlying regressive systems tract (RST) deposits record modestly improved redox conditions, likely a reflection of a receding oxygen minimum zone as base level dropped. A subsequent 3rd order base level rise and renewed expansion of the oxygen minimum zone triggered by increased surface productivity resulted in the accumulation of the organic-rich lower Oatka Creek Member. Still, the mix of abundant small and subordinate large (>10 μm) framboids preserves the record of oxygen deficient to sulfidic bottom conditions frequently interrupted by episodes of (dys)oxia. Improving redox conditions through the overlying RST were accompanied by a two-fold increase in Al and consequent dilution of the organic matter flux and authigenic trace metal uptake at the sediment–water interface. The upper half of the Oatka Creek comprises a depositional sequence not obvious from core inspection or gamma-ray signature but revealed by Mo enrichment and Al concentration profiles. Diagenetic modification of the Marcellus includes several horizons of authigenic calcium carbonate concretions and marked Ba enrichment. Both features reflect the effects of non-steady state microbial diagenesis within a methane-rich sedimentary column. |
| |
| Keywords: | Marcellus Formation Trace elements Middle Devonian Appalachian basin Framboids Redox |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
