• Marine Radiocarbon Reservoir Effect of Coastal Waters off Cape Verde Archipelago

      Monge Soares, Antonio M.; Matos Martins, Jose M.; Cardoso, Joao Luis (Department of Geosciences, The University of Arizona, 2011-01-01)
      Quantification of the marine radiocarbon reservoir effect (Delta-R) is essential in order to calibrate conventional 14C dates from marine shell samples with reliability. Delta-R also provides information concerning the intensity of coastal upwelling in marine regions influenced by this phenomenon. 14C ages of closely associated marine samples (mollusk shells) and terrestrial samples (goat bones) from So Vicente Island, Cape Verde Archipelago, permitted the first calculation of the marine 14C reservoir effect in this region. A Delta-R weighted mean value of 70 +/- 70 14C yr was obtained. This value is in accordance with the previously published oceanographic conditions of the region indicating the existence of a seasonal active upwelling regime.
    • Paired AMS 14C Dates on Planktic Foraminifera from a Gulf of Mexico Sediment Core: An Assessment of Stratigraphic Continuity

      Flower, B. P.; Hastings, D. W.; Randle, N. J. (Department of Geosciences, The University of Arizona, 2011-01-01)
      A series of recent papers has called for multiple radiocarbon dates on planktic foraminifera to assess stratigraphic continuity in deep-sea sediment cores. This recommendation comes from observations of anomalous 14C dates in planktic foraminifera from the same stratigraphic level. Potential reasons include bioturbation, downslope transport, secondary calcification, carbonate dissolution, and differential preservation. In this study, paired 14C dates on dissolution-susceptible Globigerinoides ruber and dissolution-resistant Neogloboquadrina dutertrei are used to evaluate a Gulf of Mexico sediment core. Fourteen of 15 pairs (between 8815 and 12,995 uncorrected 14C yr BP) yield concordant uncorrected 14C ages (mean difference -2 +/- 75 yr), attesting to continuous deposition at high accumulation rates (>35 cm/kyr). For 1 pair, N. dutertrei is nearly 1000 yr younger, which is difficult to explain by any combination of dissolution and bioturbation or downslope transport, given the excellent carbonate preservation and persistent laminations. The concordant ages underscore the utility of paired 14C dates in planktic foraminifera as a means of assessing stratigraphic continuity in deep-sea sediment sequences.
    • Possible Factors Causing Older Radiocarbon Age for Bulk Organic Matter in Sediment from Daihai Lake, North China

      Reuther, Joshua D.; Wu, Yanhong; Gerlach, S. Craig; Wang, Sumin; Zhou, Liping (Department of Geosciences, The University of Arizona, 2011-01-01)
      Many factors may influence the radiocarbon age results of lacustrine sediments, among which the hardwater effect is particularly important. Daihai Lake is a closed lake located in the semi-arid region of Inner Mongolia, China. High concentrations of (HCO3)- and (CO3)2- and high pH values in the lake water imply that there is a hardwater effect when using bulk lacustrine sediment samples for 14C dating. To correct the apparent 14C age, we present a pilot study based on a series of 14C ages of lake surface sediment, lake water, submerged aquatic plant (Myriophyllum), fish bone (Cyprinus carpio), and surface soil samples from and around Daihai Lake. Assuming that the relationship between the 14C/12C ratio of DIC and of atmospheric CO2 was constant (at 0.816), the hardwater effect ages calculated for the past 8000 yr would have varied from 949 to 1788 yr. Together with the reservoir effect and soil organic matter input, the hardwater effect is a major factor causing changes in apparent age when using bulk organic matter for 14C dating.
    • Royal Institute for Cultural Heritage Web-Based Radiocarbon Database

      Van Strydonck, Mark; De Roock, Edwin (Department of Geosciences, The University of Arizona, 2011-01-01)
      The radiocarbon dating laboratory at KIK-IRPA in Brussels was founded in the 1960s. From the beginning, dates were reported at more or less regular intervals in the journal Radiocarbon (Schreurs 1968) as did most of the other 14C laboratories.
    • Rudjer Boškovic Institute Radiocarbon Measurements XVI

      Obelić, Bogomil; Krajcar Bronić, Ines; Horvatinčić, Nada; Barešić, Jadranka; Rajtarić, Anita (Department of Geosciences, The University of Arizona, 2011-01-01)
      In this paper, we present dating of archaeological samples performed since our last report (Obelic et al. 2002). Included are results of samples measured by the gas proportional counting (GPC) method until the abandonment of this technique in 2007, as well as results of several series measured by both GPC and liquid scintillation counting (LSC) methods.
    • Table of Contents

      Department of Geosciences, The University of Arizona, 2011-01-01
    • Tell Sabi Abyad, Syria: Radiocarbon Chronology, Cultural Change, and the 8.2 ka Event

      Van der Plicht, J.; Akkermans, P. G.; Nieuwenhuyse, O.; Kaneda, A.; Russell, A. (Department of Geosciences, The University of Arizona, 2011-01-01)
      At Tell Sabi Abyad, Syria, we obtained a robust chronology for the 7th to early 6th millennium BC, the Late Neolithic. The chronology was obtained using a large set of radiocarbon dates, analyzed by Bayesian statistics. Cultural changes observed at ~6200 BC are coeval with the 8.2 ka climate event. The inhabitation remained continuous.
    • The Canadian Archaeological Radiocarbon Database (CARD): Archaeological 14C Dates in North America and Their Paleoenvironmental Context

      Gajewski, K.; Muñoz, S.; Peros, M.; Viau, A.; Morlan, R.; Betts, M. (Department of Geosciences, The University of Arizona, 2011-01-01)
      Databases of accumulated paleoecological and archaeological records provide a means for large-scale syntheses of environmental and cultural histories. We describe the current status of the Canadian Archaeological Radiocarbon Database (CARD), a searchable collection of more than 36,000 14C dates from archaeological and paleontological sites from across North America. CARD, built by the late Dr Richard Morlan of the Canadian Museum of Civilization, consists of uncalibrated 14C data as well as information about the material dated, the cultural association of the date (e.g. Paleoindian, Archaic, Woodland), and its geographic location. The database can be used to study questions relating to prehistoric demography, migrations, human vulnerability to environmental change, and human impact on the landscape, but biases relating to sampling intensity and taphonomy must first be accounted for. Currently, Canada and the northern United States are well represented in the database, while the southern United States is underrepresented. The frequency of 14C dates associated with archaeological sites increases through time from 15,000 cal yr BP until European contact, which likely reflects, among other factors, both the destruction of older cultural carbon due to erosion and dissolution and increasing population numbers through time. An exploratory analysis of the dates reveals their distribution in both time and space, and suggests that the database is sufficiently complete to enable quantitative analysis of general demographic trends.
    • Using the 14C Bomb Pulse to Date Young Speleothems

      Hodge, Ed; McDonald, Janece; Fischer, Matthew; Redwood, Dale; Hua, Quan; Levchenko, Vladimir; Drysdale, Russell; Waring, Chris; Fink, David (Department of Geosciences, The University of Arizona, 2011-01-01)
      Three modern speleothems were sampled at high resolution for radiocarbon analysis to identify their bomb-pulse signatures and to construct chronologies. Each speleothem exhibited a different 14C response, presumed to be related to site characteristics such as vegetation, temperature, rainfall, depth below the surface, and water pathway through the aquifer. Peak 14C activity for WM4 is 134.1 pMC, the highest cited thus far in the literature and suggestive of a lower inertia at this site. Dead carbon fractions for each stalagmite were calculated and found to be relatively similar for the 3 speleothems and lower than those derived from Northern Hemisphere speleothems. An inverse modeling technique based on the work of Genty and Massault (1999) was used to estimate soil carbon residence times. For each speleothem, mean soil 14C reservoir ages differed greatly between the 3 sites, ranging from 2-6.5 to 32-46 yr.
    • Who's That Lying in My Coffin? An Imposter Exposed by 14C Dating

      Sowada, Karin; Jacobsen, Geraldine E.; Bertuch, Fiona; Palmer, Tim; Jenkinson, Andrew (Department of Geosciences, The University of Arizona, 2011-01-01)
      In the 19th and early 20th centuries, many museums acquired Egyptian coffins containing mummies from private donors who bought them from dealers in Egypt. Owing to the unknown context of such acquisitions, it cannot be assumed that the mummified individual inside the coffin is the same person named on it. Radiocarbon dating is a key diagnostic test, within the framework of a multidisciplinary study, to help resolve this question. The dating of an adult mummy in the Nicholson Museum at the University of Sydney was therefore checked using 14C dating. For over 150 yr, mummy NM R28.2 was identified as Padiashaikhet as per his coffin, dated to the 25th Dynasty, about 725-700 BC. 14C results from samples of linen wrappings revealed that the mummy was an unknown individual from the Roman period, cal AD 68-129. The mummification technique can now be understood within its correct historical context.