• Least-Squares Fitting a Smooth Curve to Radiocarbon Calibration Data

      Knox, F. B.; McFadgen, B. G. (Department of Geosciences, The University of Arizona, 1997-01-01)
      We Fourier transformed and filtered calibration curve data to compensate for the averaging effect of radiocarbon-dating sets of adjacent tree rings. A Wiener Filter was also applied to minimize the effects of the counting errors of the dates on the resulting calibration curve and to produce a least-squares curve through the data. The method is illustrated using a short 14C-dated tree-ring sequence from New Zealand to produce a calibration curve at yearly intervals for New Zealand matai (Prumnopitys taxifolia). The resulting curve has a nominal standard error of 10 +/3 yr, which is ca. Half the average standard error of the original raw data.
    • Twenty Years of Atmospheric 14CO2 Observations at Schauinsland Station, Germany

      Levin, Ingeborg; Kromer, Bernd (Department of Geosciences, The University of Arizona, 1997-01-01)
      We present and discuss quasi-continuous long-term 14CO2 observations from the continental background station Schauinsland (48 degrees N, 8 degrees E, 1205 m asl, Black Forest, southern Germany). The observed steady decline of atmospheric 14CO2 from 1977 to 1996 can be described by a single exponential function with an e-folding time of (16.3 +/0.2) yr. Summer means (May to August) in atmospheric 14CO2 at Schauinsland compare within Delta-14C = +/4 per mil with measurements made on individual rings from a tree grown in the near vicinity of the Schauinsland site. Both data sets are slightly depleted by up to 5 if compared to maritime background measurements of atmospheric 14CO2 made at Izaña, Tenerife. This is due to the influence of fossil fuel CO2 emissions over the European continent as well as generally in mid latitudes of the Northern Hemisphere. delta-13C analyses from the Schauinsland samples show mean seasonal variations with an amplitude of 0.4, caused by atmosphere-biosphere exchange, and a mean decrease from 1977 to 1996 of delta-13C = -0.017 per mil yr-1. This trend is mainly due to an increasing quantity of fossil fuel CO2 in the atmosphere, depleted in 13C/12C ratio, and compares well to trends measured at other stations in mid-to-high northern latitudes.
    • Radiocarbon, Volume 39, Number 2 (1997)

      Department of Geosciences, The University of Arizona, 1997-01-01
    • C. E. Buck, W. G. Cavanagh and C. D. Litton. Bayesian Approach to Interpreting Archaeological Data

      Scott, Marian (Department of Geosciences, The University of Arizona, 1997-01-01)
      Reviewed by Marian Scott, Department of Statistics, University of Glasgow
    • Evidence for Late Polynesian Colonization of New Zealand: University of Waikato Radiocarbon Measurements

      Higham, T. F. G.; Hogg, A. G. (Department of Geosciences, The University of Arizona, 1997-01-01)
      We present radiocarbon determinations for 271 New Zealand archaeological samples measured at the University of Waikato Radiocarbon Dating Laboratory between 1975 and 1995. A discard protocol is applied to the series and the list culled to winnow the acceptable dates from those that may incorporate error. None of the 221 acceptable 14C determinations older than 600 BP (in the case of terrestrial samples) or 930 BP (in the case of marine and estuarine shell) extends beyond cal AD 1250. This conclusion supports the short chronology model of New Zealand prehistory presented by Anderson (1991).
    • 1997 Price List

      Department of Geosciences, The University of Arizona, 1997-01-01
    • Radiocarbon Reservoir Ages in the Gulf of California: Roles of Upwelling and Flow from the Colorado River

      Goodfriend, Glenn A. (Department of Geosciences, The University of Arizona, 1997-01-01)
      We measured apparent radiocarbon ages of live-collected, pre-bomb mollusk shells from the northern and central Gulf of California to determine the source of the reservoir ages and the reservoir age correction offsets for calibrating 14C dates of fossil samples. Reservoir ages average 860 yr in the northern Gulf and 725 yr in the central Gulf. The corresponding Delta-R values (the deviation from typical worldwide values) are 540 yr and 395 yr, respectively, with variabilities (SD) of 90 and 110 yr. This variability significantly limits the precision of calibrated 14C ages. The apparent 14C age of Colorado River water (as measured in a freshwater mussel, collected in the 1890s, before diversion of river flow) is not sufficiently high (1420 yr) to account for the high reservoir ages in the Gulf. The lack of a relation between the stable isotope composition of Gulf mollusks and their reservoir ages is further evidence that the Colorado River does not make a significant contribution to Gulf reservoir ages. Upwelling of old, deep Pacific-derived water appears to be the cause of the large reservoir ages.
    • Associate Editors

      Department of Geosciences, The University of Arizona, 1997-01-01
    • Distribution of Sites and Radiocarbon Dates in the Sierra Nevada: Implications for Paleoecological Prospecting

      Anderson, R. Scott; Smith, Susan J.; Koehler, Peter A. (Department of Geosciences, The University of Arizona, 1997-01-01)
      The number of paleoecological records for the Sierra Nevada of California has increased substantially since the compilation of Adam (1985). We examine here the geographical and temporal distribution of records within the range in order to identify areas for which "gaps" exist in our paleoecological knowledge. Seventy-two sites with paleoecological information are identified; these sites are dated with 234 radiocarbon dates. Sites occur primarily between ca. 36 degrees N and 38 degrees 30'N latitudes, and from ca. 1000 m to over 3000 m elevation on both sides of the Sierran crest, although more sites have been analyzed on the west side of the crest than the east side. In general, packrat (Neotoma) midden series are located at the lowest elevations, meadow and marsh cores originate from mid-elevations, and lake sediments have been analyzed from the highest elevations. Significant gaps in our knowledge occur for much of the east side of the crest, for both sides of the range above modern treeline, and for time periods older than the latest Pleistocene.