• 14C Depth Profiles as Indicators of Trends of Climate and 14C/12C Ratio

      Brown, Robert H. (American Journal of Science, 1986-01-01)
      Composite curvature averages for 14C age depth profiles of deep ocean sediment, continental sediment, and soil each indicate a global trend for 14C age increment per cm depth to increase with 14C age over the range for which a definitive statistical sample is available. The global trend indicated for peat profiles is constant 14C age increment per cm depth over the past 10,000 14C yr. Correlation coefficients between changes in 14C yr/cm and maximum profile thickness contradict compaction as an adequate explanation for the global trend indicated by sediment and soil profiles. This trend must be explained by additional factors such as progressively decreasing contamination from older carbon, increasing cosmic ray intensity, decreasing geomagnetic intensity, diminishing 12C in the active biosphere during profile accumulation, and climate factors affecting the rate of accumulation. The diverse trend of peat profiles may indicate climatic conditions more favorable to peat growth during the earlier portion of the past 10,000 yr.
    • Discordant Ages Related to Reservoir Effect of Associated Archaeologic Remains from the Tunel Site, Beagle Channel, Argentine Republic

      Albero, Miguel C.; Angiolini, Fernando E.; Piana, Ernesto L. (American Journal of Science, 1986-01-01)
      Evidence of a tradition of human maritime adaptation was recovered from various sites at Beagle Channel dating back to ca 6000 yr BP. Final occupations date to European settlement in the 19th century. The Túnel site exhibits discontinuous human occupation ranging from 6000 to 500 yr BP, represented by different archaeologic remains in each layer. Associated charcoal, mollusk shells, and Lama guanicoe and Arctocephalus australis bones were dated. Shells and Arctocephalus are consistently older than charcoal, demonstrating the reservoir effect at Beagle Channel. Results encourage further work in the area to evaluate the spatial and temporal magnitude of the effect.
    • Gif Natural Radiocarbon Measurements X

      Delibrias, Georgette; Guillier, M.-T.; Labeyrie, Jacques (American Journal of Science, 1986-01-01)
    • Illinois State Geological Survey Radiocarbon Dates VIII

      Liu, Chao-Li; Riley, Kerry M.; Coleman, Dennis D. (American Journal of Science, 1986-01-01)
    • University of Texas at Austin Radiocarbon Dates XV

      Valastro, S.; Mott Davis, E.; Varela, Alejandra G.; Lisk, Susan V. (American Journal of Science, 1986-01-01)
    • University of Wisconsin Radiocarbon Dates XXIII

      Steventon, Raymond L.; Kutzbach, John E. (American Journal of Science, 1986-01-01)