Seasonal radiocarbon reservoir ages for the 17th century James River,Virginia estuary |
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| Institution: | 1. Department of Earth and Planetary Sciences, University of California, Davis, CA 95616, USA;2. Department of Marine Science, Coastal Carolina University, Conway, SC 29528, USA;3. Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA;4. Department of Ocean Sciences, University of California, Santa Cruz, CA 95064, USA;1. Institute for Geography, Universität zu Köln, Köln, Germany;2. School of Biological, Earth and Environmental Sciences, University of New South Wales, Kensington, Australia;3. Institute of Geological Sciences, Universität Bern, Bern, Switzerland;4. Chair of Geomorphology & BayCEER, Universität Bayreuth, Bayreuth, Germany;1. Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, PA 19104, USA;2. Scripps Institution of Oceanography, Geosciences Research Division, La Jolla, CA, 92037, USA;3. Department of Geosciences, North Dakota State University, Fargo, ND 58108, USA;1. Laboratory of Biomolecular Stratigraphy, E.T.S.I. Minas, Universidad Politécnica de Madrid, C/ Ríos Rosas 21, Madrid 28003, Spain;2. Instituto Geológico y Minero de España, C/Ríos Rosas 23, 28003 Madrid, Spain;1. Key Laboratory of Tourism and Resources Environment in Universities of Shandong, Taishan University, 271000 Taian, China;2. College of Resource Environment and Tourism, Capital Normal University, 100048 Beijing, China;3. Center for Nuclear Technologies, Technical University of Denmark, DTU Risø Campus, Frederiksborgvej 399, 4000 Roskilde, Denmark;4. Nordic Laboratory for Luminescence Dating, Department of Geoscience, University of Aarhus, Risø Campus, Frederiksborgvej 399, 4000 Roskilde, Denmark;5. Beijing Jing Yuan School, 100040 Beijing, China;1. Institute for Geology, University of Innsbruck, 6020, Austria;2. ARC Centre of Excellence for Australian Biodiversity and Heritage, GeoQuest Research Centre, University of Wollongong, 2500, Australia;1. Leibniz Institute for Applied Geophysics, Stilleweg 2, Hannover 30655, Germany;2. Kogakkan University, 1704 Kodakushimoto-cho, Ise, 516-8555 Japan;3. Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, D-04103 Leipzig, Germany;4. Center for Nuclear Technologies, Technical University of Denmark, DTU Risø Campus, DK-4000, Roskilde, Denmark |
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| Abstract: | This study utilizes a combined stable isotope and 14C dating approach to determine the radiocarbon reservoir age correction, ΔR, for the James River, Virginia estuary from 17th century Crassostrea virginica shells of known collection dates. ΔR, which can vary spatially and temporally, is a locality-specific adjustment applied to the global ocean reservoir, R, to further account for the offset between the atmospheric and marine 14C calibration curves. To assess the temporal variability in ΔR, continuous δ18O sampling along the oyster shell hinge provides a seasonal record throughout the oyster's life. This is then used to identify sampling locations for 14C measurements based on calcite precipitated during the Summer (>19 °C) and Fall through Spring (F-Sp, <15 °C) months. The resulting seasonal ΔR values range from −151 ± 46 to +109 ± 55 14C years (260 years) due to changes in the contribution and age of dissolved inorganic carbon (DIC) from marine and freshwater sources in the James River estuary. The F-Sp samples display a larger ΔR range than the Summer samples, as do the shells precipitated during drought conditions (1606–1612) when compared to shells from the remainder of the 17th century. The largest intrashell ΔR variability, 195 14C years, is similarly found in a drought shell and is attributed to variability caused by the extreme regional 1606–1612 drought. Early land use changes related to European development and farming practices also altered the age of DIC in the James River estuary. We estimate that the soil inorganic carbon (SIC) contributing to freshwater DIC ranged from 0 to ∼1800 years old and reflected both the drought and land use changes that occurred during the 17th century. Using only the Summer samples, which represent the majority of shell calcite, we obtain a mean ΔR = −32 ± 11 14C years (1σ) for 17th century James River estuary ΔR at the very onset of European colonization. Employing a seasonally resolved sampling method will provide the greatest constraint on 14C measurements in an estuarine environment where multiple carbon sources can fluctuate on seasonal timescales and as a result of large scale environmental change. |
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| Keywords: | Radiocarbon Reservoir age (ΔR) Sclerochronology Dissolved inorganic carbon (DIC) Estuary |
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