• Near-Zero Delta-14C Values at 32 Kyr Cal BP Observed in the High-Resolution 14C Record from U-Th Dated Sediment of Lake Lisan

      van der Borg, K.; Waldman, Waldmann N.; Goldstei, Goldstein L. (Department of Geosciences, The University of Arizona, 2004-01-01)
      A high-resolution atmospheric radiocarbon record has been obtained for the interval of 17-36 kyr from U/Th dated aragonite sediment of Lake Lisan. Reservoir age corrections were applied with reservoir ages of 200, 1250, and 2000 yr, which correlate with the different water levels of the lake. The present 14C record for Lake Lisan shows near resemblance with that of Lake Suigetsu: both converge to the value of Delta-14C approximately 0 per mil at 32 kyr cal BP. Both also show significant differences compared to other reported high-resolution 14C records (e.g. Iceland Sea, Cariaco basin, and Bahamas speleothem). This inconsistency should be addressed by re-assessment of the basic assumptions behind the determination of calendar ages of the various records.
    • On the Erosive Trail of a 14th and 15th Century Hurricane in Connecticut (USA) Salt Marshes

      van de Plassche, O.; Wright, A. J.; van der Borg, K.; de Jong, A. F. M. (Department of Geosciences, The University of Arizona, 2004-01-01)
      This paper examines if an erosive hiatus found in the peat stratigraphy and marsh-accumulation record from northwest Hammock River Marsh (HRM), Connecticut (CT) can be attributed to a 14th or a 15th century hurricane, each documented by a radiocarbon-dated overwash fan in Succotash Marsh (SM) (Rhode Island) about 90 km to the east. Given that (i) the best estimate age range for the 15th century overwash deposit in SM (1400-1440 cal AD, 2 sigma) overlaps entirely with that for first plant growth after erosion at HRM (1390-1450 cal AD, 2 sigma), while the best estimate age range for the 14th century overwash deposit (1290-1410 cal AD, 2 sigma) overlaps just 10 yr, and (ii) interpretation of the available stratigraphic and sedimentary evidence from HRM suggests that a high-energy event offers the simplest explanation for the observed marsh erosion, we conclude that a plausible link exists between the 15th century hurricane and the marsh erosion in HRM. The best estimate age range for the 14th century hurricane appears to overlap for 91% with the age range for the first plant growth (1290-1400 cal AD, 2 sigma) following marsh erosion in East River Marsh (CT), located about 12 km west of HRM. These results imply that erosive boundaries in salt-marsh peat deposits have potential as markers of past hurricane activity.