See more from this Division: Topical Sessions
See more from this Session: Paleozoic Oceanographic and Climatic Changes: Evidence from Seawater Geochemistry and Sedimentology Records I
Abstract:
The Middle Ordovician (Arenig-Llanvirn) San Juan (Argentine Precordillera) and Table Point (Western Newfoundland) formations provide an excellent starting point for exploring potential effects of oceanic circulation on marine sulfur-isotope records. The San Juan and Table Point formations represent deposition in shallow and mid-shelf to deep-shelf environments, respectively. Sulfur-isotope curves for both formations, constructed via isotopic analysis of carbonate-associated sulfate (CAS) show short-term (20-30m) isotopic shifts of up to 6 that are superimposed over a longer-term isotopic signal. Isotopic values are independent of lithology and depositional environment, suggesting that short-term isotopic variation may represent a global phenomenon related to greenhouse oceanographic conditions. We suggest that short-term sulfur-isotope variation recorded in these units reflects transient changes in the extent of oceanic bottom-water anoxia, resulting in variable redox cycling (BSR and sulfide oxidation) in deep-ocean environments. Here we present new data regarding reactive iron content, sulfur-isotope composition of sedimentary pyrite, and oxygen-isotope composition of trace sulfate to explore potential changes in redox cycling on initial C- and S-isotope datasets.
See more from this Division: Topical Sessions
See more from this Session: Paleozoic Oceanographic and Climatic Changes: Evidence from Seawater Geochemistry and Sedimentology Records I