Jason A Rech, Christina N Tenison, Alexander Baldasare, Brian S Currie
{"title":"RADIOCARBON DATING AND FRESHWATER RESERVOIR EFFECTS OF AQUATIC MOLLUSKS WITHIN FLUVIAL CHANNEL DEPOSITS IN THE MIDWESTERN UNITED STATES","authors":"Jason A Rech, Christina N Tenison, Alexander Baldasare, Brian S Currie","doi":"10.1017/rdc.2023.93","DOIUrl":null,"url":null,"abstract":"<p>Late Quaternary fluvial channel deposits are notoriously difficult to date. In the midwestern United States, shells of aquatic mollusks can be found within many fluvial channel sediments and therefore can be radiocarbon (<span>14</span>C) dated to determine the age of the deposits. However, carbonate platform rocks are abundant in this region, potentially causing freshwater <span>14</span>C reservoir effects (FRE) in mollusk shells. We <span>14</span>C dated 11 aquatic gastropod and bivalve shell samples from specimens collected live from a stream in southwestern Ohio during three different years to assess the modern <span>14</span>C reservoir effect. Modern samples yielded an average <span>14</span>C FRE<span>modern</span> of 518 ± 65 <span>14</span>C yrs for 2020 (n=5), 640 ± 34 <span>14</span>C yrs for 2021 (n=2), and 707 ± 76 <span>14</span>C yrs for 2022 (n=4). We also <span>14</span>C dated matched pairs of organic wood or charcoal and aquatic mollusk shells from late Pleistocene and Holocene deposits in the Four Mile Creek floodplain to determine the FRE<span>fossil</span>. These samples, free of any potential influence from nuclear bomb testing, yielded an overall weighted mean FRE<span>fossil</span> of 1029 ± 345 <span>14</span>C yrs. We then assess the advantages and limitations of both the FRE<span>modern</span> and FRE<span>fossil</span> methods for determining freshwater reservoir effects. Finally, we apply the FRE<span>fossil</span> correction to a series of shell ages from fluvial terrace deposits as a case study. The results indicate that although there is a <span>14</span>C FRE in streams from the midwestern United States, aquatic shells can provide robust age control on fluvial channel deposits. More research is needed to understand the spatial and temporal variability of FREs, as well as any species effects, among various watersheds across the midwestern United States.</p>","PeriodicalId":21020,"journal":{"name":"Radiocarbon","volume":"42 2","pages":""},"PeriodicalIF":2.0000,"publicationDate":"2023-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Radiocarbon","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1017/rdc.2023.93","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
引用次数: 0
Abstract
Late Quaternary fluvial channel deposits are notoriously difficult to date. In the midwestern United States, shells of aquatic mollusks can be found within many fluvial channel sediments and therefore can be radiocarbon (14C) dated to determine the age of the deposits. However, carbonate platform rocks are abundant in this region, potentially causing freshwater 14C reservoir effects (FRE) in mollusk shells. We 14C dated 11 aquatic gastropod and bivalve shell samples from specimens collected live from a stream in southwestern Ohio during three different years to assess the modern 14C reservoir effect. Modern samples yielded an average 14C FREmodern of 518 ± 65 14C yrs for 2020 (n=5), 640 ± 34 14C yrs for 2021 (n=2), and 707 ± 76 14C yrs for 2022 (n=4). We also 14C dated matched pairs of organic wood or charcoal and aquatic mollusk shells from late Pleistocene and Holocene deposits in the Four Mile Creek floodplain to determine the FREfossil. These samples, free of any potential influence from nuclear bomb testing, yielded an overall weighted mean FREfossil of 1029 ± 345 14C yrs. We then assess the advantages and limitations of both the FREmodern and FREfossil methods for determining freshwater reservoir effects. Finally, we apply the FREfossil correction to a series of shell ages from fluvial terrace deposits as a case study. The results indicate that although there is a 14C FRE in streams from the midwestern United States, aquatic shells can provide robust age control on fluvial channel deposits. More research is needed to understand the spatial and temporal variability of FREs, as well as any species effects, among various watersheds across the midwestern United States.
期刊介绍:
Radiocarbon serves as the leading international journal for technical and interpretive articles, date lists, and advancements in 14C and other radioisotopes relevant to archaeological, geophysical, oceanographic, and related dating methods. Established in 1959, it has published numerous seminal works and hosts the triennial International Radiocarbon Conference proceedings. The journal also features occasional special issues. Submissions encompass regular articles such as research reports, technical descriptions, and date lists, along with comments, letters to the editor, book reviews, and laboratory lists.