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This data set includes a variety of bulk organic carbon, lignin-phenol biomarker, and sedimentation rate data from a set of sites in the Blackwater Marsh in Chesapeake Bay. At each site, a short core was taken, and all data is organized according to depth below the marsh surface. Data includes: Bulk %OC, bulk %N, atomic carbon:nitrogen ratios, stable carbon isotopes (d13C) Lignin-phenol biomarker parameters, including 8, Ad:Alv, C:V, S:V, and the individual concentrations of each lignin-phenol (in lambda units, or mg per 100 mg OC). Pb-210 and Cs-137 activities Sediment bulk densities In addition to the sediment core data, we are also including d13C values from vegetation samples collected from each of the marsh...
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The deposits of Eocene Lake Gosiute that constitute the Green River Formation of Wyoming contain numerous tuff beds that represent isochronous, correlatable stratigraphic markers. Tuff beds selected for 40Ar/39Ar analysis occur within laminated mudstone, are matrix supported, and lack evidence of reworking. These tuffs contain 2%?15% euhedral phenocrysts of quartz, plagioclase, sanidine, biotite, and minor amphibole, pyroxene, and zircon, encased in a matrix of altered glassy ash. Air abrasion and handpicking under refractive- index oils were required to obtain clean, unaltered phenocrysts of sanidine. 40Ar/39Ar age determinations from single-crystal and <1 mg multigrain aliquots of sanidine and biotite allowed...
Understanding the time scales and pathways for response and recovery of rivers and floodplains to episodic changes in erosion and sedimentation has been a long standing issue in fluvial geomorphology. Floodplains are an important component of watershed systems because they affect downstream storage and delivery of overbank flood waters, and they also serve as sources and temporary sinks for sediments and toxic substances delivered by river systems. Here, 14C and 137Cs isotopic dating methods are used along with ages of culturally related phenomena associated with mining and agriculture to determine rates of sedimentation and morphologic change for a reach of the upper Mississippi River and adjacent tributaries in...
    map background search result map search result map 40Ar/39Ar geochronology of the Eocene Green River Formation, Wyoming Changes in Organic Carbon Source and Storage with Sea Level Rise-Induced Transgression in a Chesapeake Bay Marsh Changes in Organic Carbon Source and Storage with Sea Level Rise-Induced Transgression in a Chesapeake Bay Marsh 40Ar/39Ar geochronology of the Eocene Green River Formation, Wyoming