• Radiocarbon Chronology of the Late Pleistocene-Holocene Paleogeographic Events in Lake Baikal Region (Siberia)

      Krivonogov, S. K.; Takahara, Hikaru; Kuzmin, Yaroslav V.; Orlova, Lyobov A.; Jull, A. J. Timothy; Nakamura, Toshio; Miyoshi, Norio; Kawamuro, Kimiyasu; Bezrukova, Elena V. (Department of Geosciences, The University of Arizona, 2004-01-01)
      New radiocarbon dates obtained from Late Pleistocene and Holocene deposits of the southern, eastern, and northern shores of Lake Baikal in 1995-2001 are presented, and the most important results of paleoenvironmental studies based on 14C data are discussed. The following paleogeographic events were verified with the help of 14C dating: 1) first Late Pleistocene glaciation (Early Zyryan); 2) Middle Zyryan interstadial; 3) loess formation during the Late Zyryan (Sartan) deglaciation; 4) warm and cold events in the Late Glacial; and 5) vegetation changes and forest successions during the Late Glacial and Holocene.
    • Radiocarbon in the Water Column of the Southwestern North Pacific Ocean—24 Years After Geosecs

      Povinec, Pavel P.; Aramaki, Takafumi; Burr, George S.; Jull, A. J. Timothy; Kwong, Laval Liong Wee; Togawa, Orihiko (Department of Geosciences, The University of Arizona, 2004-01-01)
      In the framework of the Worldwide Marine Radioactivity Studies (WOMARS) project, water profile samples for radiocarbon measurements were taken during the IAEA97 cruise at 10 stations in the southwestern North Pacific Ocean. While 14C concentrations were rapidly decreasing from the surface (∆14C about 100 ppm) down to about 800 m at all visited stations (∆14C about -200 ppm), the concentrations below 1000 m were almost constant. Some stations were in proximity to the GEOSECS stations sampled in 1973; thus, 14C profiles could be compared after a 24-yr interval. Generally, 14C concentrations had decreased in surface waters (by 50-80 ppm) and increased (by about the same amount) in intermediate waters when compared with GEOSECS data. In deep waters (below 1000 m), the observed 14C concentrations were similar to GEOSECS values. The bomb-produced 14C inventory had increased by more than 20% over the 24 yr from 1973 to 1997 and was estimated to be about (32 +/5) 10^12 atom m-2, with an annual 14C flux of (1.3 +/0.3) 10^12 atom m^-2 yr-1. The results suggest that bomb-produced 14C has been advected northwards by the Kuroshio Current and the Kuroshio Extension and stored in the intermediate layer as North Pacific Intermediate Water.