Roelf P. Beukens

Diet and ethnicity during the Viking colonization of northern Scotland: evidence from fish bones and stable carbon isotopes

Diet and ethnicity are strongly related. Recent work on fish-bone ratios and stable carbon isotopes suggest that the Vikings increased the fish contribution to the diet of Orkney and Shetland by a greater investment in deep-sea fishing.

RADIOCARBON DATES FROM NEOLITHIC AND BRONZE AGE HUNTER-GATHERER CEMETERIES IN THE CIS-BAIKAL REGION OF SIBERIA

Extensive radiocarbon dating of human remains from Neolithic and Bronze Age hunter-gatherer cemeteries in the Cis-Baikal region of Siberia has been undertaken as a part of the multidisciplinary examination of this material conducted by the Baikal Archaeology Project (BAP; http:// baikal.arts.ualberta.ca). Due to the large number of analyzed samples, this paper reports the 14C results only in the context of the basic archaeological information about each of the cemeteries. Comprehensive evaluation, analysis, and interpretation of this entire data set will be undertaken in separate publications. In fact, the dates for one such cemetery have already been examined on 2 recent occasions (Weber et al. 2004, 2005).

Paleopedology of Middle Wisconsin/Weichselian paleosols in the Mérida Andes, Venezuela

Abstract Buried Spodosols (podzols) within a thick lithostratigraphic section in the northern Venezuelan Andes are interbedded with tills and a succession of multicyclic lacustrine clays, silts and sands from the early and middle stades of the Wisconsinan/Weichselian Glaciation. The peats, dated by AMS radiocarbon, allow calculations of the time required for pedogenesis. These Spodosols were studied to determine compositional changes from initial to full soil development. During lake low water stands, peats of variable thickness developed, along with soils belonging to the Spodosol order. On a relative time scale, the initial stage of soil genesis produced peat with a weathered mineral zone (Bs)—initial spodic horizon of a few centimeters thickness. With a longer time for soil genesis of a few centuries, a thin Spodosol developed with an E/Bs horizon sequence. With still longer time spans of a few thousand years, between 55 and 60 ka, more mature Spodosols with E/Bs/Cox/Cu profiles formed beneath very thick peat in conjunction with groundwater fluctuations. The lowermost peat (VII) in the section varies from 15 to 26.5 cm in thickness. The paleosols are sandy, with little evidence of either clay transformations, or silt accretion from airfall influx, apparent from the particle size analysis. XRD analysis of the clay fraction shows minor weathering of illite to vermiculite and chlorite in the Bs horizons. Chemically extractable forms of Fe and Al show increases of both soluble and insoluble minerals from the E to the Bs horizons in the buried Spodosols, a considerably different trend compared with the surface soils (Entisols). Geochemical trace element analysis shows a moderate degree of translocation of soluble chemical elements from the E to the Bs horizons.

A third generation 14C accelerator mass spectrometer

Abstract A description is provided of the critical features of a third generation accelerator mass spectrometer system designed to provide precision isotopic measurements of 14C and other long-lived cosmogenic isotopes. Using graphite samples, it is expected that this instrument will measure the ratio 14C/12C for each sample with a precision better than 0.5% when corrected for fractionation using a measured 13C/12C ratio. The throughput is expected to exceed a rate of 3000 samples/year.

Charge ratio mass spectrometry of heavy elements

Abstract A simple method of stable element assay at the parts per billion level using a sequence of charge changes at MeV ion energies has been demonstrated. Isotopic ratios and abundances of platinum have been studied using this technique in nickel sulphide and copper samples. Silver isotopic distributions have also been investigated in a number of terrestrial and meteoritic materials. A similar charge changing sequence between electrostatic analyzers at keV ion energies was shown to reduce backgrounds for a mass independent search of fractionally charged particles. The methods described form the bases of a broad band mass spectroscopic system under development at IsoTrace.

Radiocarbon accelerator mass spectrometry: background and contamination

Abstract Since the advent of radiocarbon accelerator mass spectrometry (AMS) many studies have been conducted to understand the background from mass spectrometric processes and the origins of contamination associated with the ion source and sample preparation. By studying the individual contributions a better understanding of these processes has been obtained and it has been demonstrated that it is possible to date samples reliably up to 60000 BP.

Quantum mechanical effects on sputter source isotope fractionation

Abstract The negative ion production probabilities for ions of differing masses have been calculated for a simplified sputter source geometry using the formalism developed by Norskov and Lundqvist. The isotope fractionation derived from this probability is, as expected, a strongly varying function of the sputter cathode surface conditions. The results of these calculations using the carbon isotopes as an example are discussed with regard to their implications for accelerator mass spectrometry (AMS).

Development of an ion microprobe stage for accelerator mass spectrometry

Abstract This report summarises the design and construction of an ion microprobe attachment under development for the accelerator mass spectrometry (AMS) laboratory at Toronto. The sample chamber and the stage assembly, which is movable in three dimensions, are described, and a synopsis of relevant ion-optical and light-optical (viewing) design work is appended.

Isotrace radiocarbon analysis — equipment and procedures

Abstract The configuration of the IsoTrace Accelerator Mass Spectrometer for radiocarbon analysis and the procedures for its use are discussed.

New Evidence from a Black Mat Site in the Northern Andes Supporting a Cosmic Impact 12,800 Years Ago

Previous work has ascribed a cosmic impact origin to black, high-temperature, carbon-encrusted beds (2–3 cm thick), associated with the Younger Dryas readvance of ice at 12.8 ka during the Late Glacial in the northern Andes of Venezuela. The evidence for this includes carbon spherules, aluminosilicate melt rocks, melted coatings of glass-like amorphous carbon, and Fe-Mn on sands and clasts derived from local felsic gneiss and granite. These sediments have been subjected to renewed investigation using high-resolution scanning electron microscopy and energy-dispersive spectrometry, and new data show that spherules at site MUM7B exhibit unique morphologies and compositions. Molar oxide weight percentages prove the spherules are not volcanic and show little overlap with cosmic materials. Spherule microstructures display quench melting and, thus, could not have formed from slow geological authigenic, diagenetic, or metamorphic processes. Instead, geochemical values for the Venezuelan samples plot within the limits of impact-related materials, including tektites, ejecta, and impact spherules from a number of craters and strewnfields (cf. Chicxulub Crater, Chesapeake Bay Crater, Tunguska, Australasian tektite field, Lake Bosumtwi Crater, Ries Crater, and others). These results are identical to previously reported spherules from the Younger Dryas boundary layer (YDB) on three continents, North America, Europe, and Asia, and the most likely origin is from a cosmic impact/airburst 12.8 ka, as previously proposed. The MUM7B site is one of the two southernmost sites (Venezuela and Peru) in South America, thus extending the evidence supporting the YDB impact event into a new hemisphere on a new continent.