• New Dating Evidence for North Sea Trade between England, Scotland, and Norway in the 11th Century AD

      Hall, D. W.; Cook, G. T.; Hamilton, W. D. (Department of Geosciences, The University of Arizona, 2010-01-01)
      This study follows on from previous research at Perth, Scotland, in which we dated carbonized food residues removed from the external surface of rim sherds of cooking pots of London Sandy Shellyware pottery (Museum of London Pottery Fabric Code SSW). The 15 residues that were dated produced 14C ages between 910 +/- 35 and 1085 +/- 40 BP. We have now carried out radiocarbon measurements on similar residues from the same fabric obtained from the Billingsgate excavations in London and the Bryggen excavations in Bergen, Norway. The London and Bergen measurements gave age ranges of 905 +/- 35 to 1115 +/- 35 BP and 920 +/- 35 to 1055 +/- 35 BP, respectively, both very similar to the Perth age range. The measurements at each site are in agreement with our Bayesian model assumption that they belong to a single phase of activity. The model estimates the introduction of London Sandy Shellyware in London to cal AD 820-1020, in Perth to cal AD 930-1020, and in Bergen to cal AD 980-1030 (95% probability). Further modeling predicts that it fell out of use in the reverse order.
    • Pre-Bomb Marine Reservoir Variability in the Kimberley Region, Western Australia

      O'Connor, Sue; Ulm, Sean; Fallon, Stewart J.; Barham, Anthony; Loch, Ian (Department of Geosciences, The University of Arizona, 2010-01-01)
      New Delta-R values are presented for 10 known-age shells from the Kimberley region of northwest Australia. Previous estimates of Delta-R for the Kimberley region are based on only 6 individual shell specimens with dates of live collection known only to within 50 yr (Bowman 1985a). Here, we describe the results of our recent attempts to constrain Delta-R variability for this region by dating a suite of known-age pre-AD 1950 shell samples from the Australian Museum and Museum Victoria. A regional Delta-R of 58 +/- 17 14C yr for open waters between Broome and Cape Leveque is recommended based on 7 of these specimens. The criteria used to select shells for dating and inclusion in the regional mean are discussed.
    • Development of Radiocarbon Dating Methods for Modern Bone Collagenization

      Kim, K. J.; Hong, W.; Park, J. H.; Woo, H. J.; Hodgins, G.; Jull, A. J. T. (Department of Geosciences, The University of Arizona, 2010-01-01)
      The relationship between temperature and time required for collagenization using modern bone samples was investigated. Gelatinized samples of bone collagen were filtered to selectively collect different molecular weight fractions. The results of this study suggest that heating to 70 degrees C for a duration of 12 hr provides the optimal conditions for gelatinization.
    • Approaches to Estimating Marine Protein in Human Collagen for Radiocarbon Date Calibration

      Dewar, Genevieve; Pfeiffer, Susan (Department of Geosciences, The University of Arizona, 2010-01-01)
      Determining the appropriate approach to calibrating radiocarbon dates is challenging when unknown and variable fractions of the carbon sample are derived from terrestrial and marine systems. Uncalibrated dates from a large number of human skeletons from Western Cape and Southern Cape locales, South Africa (n = 187), can be used to explore alternate approaches to the marine carbon correction. The approach that estimates theoretically expected minimum and maximum values for marine carbon ("expected") is compared to the approach that estimates observed minimum and maximum values ("observed"). Two case studies are explored, wherein skeletons interred together have non-overlapping conventional 14C ages. The case from the Western Cape is explored through carbon isotope values; the case from the Southern Cape uses nitrogen isotope values. In both cases, the approach using observed endpoints yields better date calibration results. Analysis of the large sample shows that mean values for estimated dietary % Marine, as calculated using expected and observed protocols, are significantly different. We conclude that the observed protocol is preferred, and that improved measures of the local marine reservoir (∆R) are needed for this region.
    • The Phytolith 14C Puzzle: A Tale of Background Determinations and Accuracy Tests

      Santos, Guaciara M.; Alexandre, Anne; Coe, Heloisa G.; Reyerson, Paul E.; Southon, John R.; D, Cacilda N. (Department of Geosciences, The University of Arizona, 2010-01-01)
      Over the past decades, analysis of occluded carbon in phytoliths (opaline silica mineral bodies that form in and between plant cells) has become a workhorse of paleoclimate and archaeological studies. Since different plant types exhibit distinctive phytolith morphologies, their assemblages are used in identifying vegetation histories or food culture adaptations. A few direct radiocarbon AMS measurements of phytoliths have been carried out, but these measurements are difficult due to the low concentrations of phytoliths in some plant species, and the small amount of C per phytolith (2%). In addition, no phytoliths samples of a known 14C age are available to verify measurement accuracy and precision, and to check sample preparation protocols. Background corrections are also difficult to address due to the lack of suitable material. In this work, we designed a procedure to quantify a suitable blank using SiO2 powder samples (close to the opal structure, and free of 14C). The full phytolith extraction showed high carbon contamination components: a) ~3 g of modern C and ~2 g of dead C. We also performed accuracy tests on large phytolith-occluded carbon samples extracted from soils and harvested plants. The unexpected 14C ages in some of the results triggered further investigations of possible sources of carbon contamination.
    • Simple Pretreatment Method Development for Iron and Calcium Carbonate Samples

      Park, Junghun; Hong, Wan; Choi, Han Woo; Kim, Joonkon; Kim, Gi Dong (Department of Geosciences, The University of Arizona, 2010-01-01)
      Since iron artifacts generally contain trace amounts of carbon, an iron sample needs to be relatively large, as compared to other materials, and a specially designed combustion system is required. An elemental analyzer (EA) was used for the combustion of iron without any special chemical treatment. CO2 gas with 1 mg of carbon was obtained from the combustion of an iron artifact by using an EA and reduced to graphite for accelerator mass spectrometry (AMS) measurement. In this work, AMS dating results done at the Korea Institute of Geoscience and Mineral Resources (KIGAM) for several ancient iron artifacts are presented and compared with independently estimated ages. This method was found to be useful for the pretreatment of iron artifacts that contained 0.1% carbon. A simple pretreatment method using an EA was also applied to calcium carbonate (CaCO3) samples. Samples were preheated overnight at 100-300 C, without any special chemical treatment. This removed modern CO2 contamination and the background level decreased to a comparable value measured in samples treated with phosphoric acid under vacuum.
    • Radiocarbon in the Air of Central Europe: Long-Term Investigations

      Svetlik, I.; Povinec, P. P.; Molnár, M.; Vána, M.; Šivo, A.; Bujtás, T (Department of Geosciences, The University of Arizona, 2010-01-01)
      Regional levels of radiocarbon have been monitored in order to investigate the impact of fossil fuel combustion on the activity of atmospheric 14CO2 in central Europe. Data from atmospheric 14CO2 monitoring stations in the Czech Republic, Slovakia, and Hungary for the period 2000-2008 are presented and discussed. The Prague and Bratislava monitoring stations showed a distinct local Suess effect when compared to the Jungfraujoch clean-air monitoring station. However, during the summer period, statistically insignificant differences were observed between the low-altitude stations and the high-mountain Jungfraujoch station. 14C data from the Hungarian monitoring locality at Dunafldvr and the Czech monitoring station at Kosetice, which are not strongly affected by local fossil CO2 sources, indicate similar grouping and amplitudes, typical for a regional Suess effect.
    • AMS Dating of Human Bone from Cova de la Pastora: New Evidence of Ritual Continuity in the Prehistory of Eastern Spain

      McClure, Sarah B.; García Puchol, Oreto; Ulleton, Brendan J. (Department of Geosciences, The University of Arizona, 2010-01-01)
      We present the results of 10 AMS radiocarbon dates for Cova de la Pastora (Alcoi, Alicante), a burial cave attributed to the Late Neolithic/Chalcolithic in eastern Spain. The direct dating of 10 human mandibles from Cova de la Pastora indicates that the cave was used as a burial place from the Late Neolithic/Chalcolithic to the Bronze Age. These dates reveal a continuity of ritual use not previously identified at the site. This case also serves to highlight the utility of revisiting historic excavations and museum collections with modern techniques to shed new light on the prehistoric human record.
    • Radiocarbon Dating, Stable Isotope Analysis, and Diet-Derived Offsets in 14C Ages from the Klin-Yar Site, Russian North Caucasus

      Higham, T.; Warren, R.; Belinskij, A.; Härke, H.; Ood, R. (Department of Geosciences, The University of Arizona, 2010-01-01)
      The influence of geothermally derived carbon on the radiocarbon dating of human bone from archaeological sites is poorly understood and has rarely been rigorously examined. This study identifies a previously unknown reservoir effect at the archaeological site of Klin-Yar in the Russian North Caucasus. AMS-dated human bones yielded results that were older than expected when compared with dates of coins found in the same grave contexts. We investigated the reasons for this offset by AMS dating modern plant, fish, and water samples to examine the source of the old carbon. We identified a potential source in geothermally derived riverine and spring water, with an apparent age of several thousand years, and hypothesize that carbon from here is being transferred through the food chain to humans. If humans consume resources from the local rivers, such as fish, then they ought to be affected by this reservoir offset. An extensive analysis of carbon and nitrogen isotopes of human and animal bone showed evidence for a mixed diet that may be masking the amount of freshwater-derived protein being consumed. Due to the highly variable nature of the 14C offset (0 to ~350 yr), no suitable average correction factor is applicable to correct for the human dates at the site. A 14C chronology based on dates obtained from terrestrial ungulate bones, which we subsequently obtained, is instead a more reliable indicator of age.
    • The 4000-Year-Old "Longshan Giant" Discovered in Shaanxi Province, China

      Yang, Yachang; Zhu, Yizhi (Department of Geosciences, The University of Arizona, 2010-01-01)
      A human skeleton of phenomenal size was uncovered during the excavation of a prehistoric site located in the city of Shangnan, Shaanxi province, China, in 2006. The skeleton dates to 4240-4100 cal yr BP, corresponding to the Longshan culture (4400-4000 yr ago). The skeletal characteristics point to a young male 16-18 yr old with a height of 193 cm. This is the tallest skeleton ever discovered in prehistoric China, and thus we name him the "Longshan Giant." The giant appears to be of the Mongoloid race and has many physical characteristics that are similar to those of modern southern Asians. Upon closer examination, 3 drilled holes of 5 cm in diameter were found in the right parietal bone of the skull. No rationale exists yet to explain the presence of these holes.
    • The Radiocarbon Chronology of El Mirón Cave (Cantabria, Spain): New Dates for the Initial Magdalenian Occupations

      Straus, Lawrence Guy; González Morales, Manuel R. (Department of Geosciences, The University of Arizona, 2010-01-01)
      Three additional radiocarbon assays were run on samples from 3 levels lying below the classic (+/- 15,500 BP) Lower Cantabrian Magdalenian horizon in the outer vestibule excavation area of El Mirón Cave in the Cantabrian Cordillera of northern Spain. Although the central tendencies of the new dates are out of stratigraphic order, they are consonant with the post-Solutrean, Initial Magdalenian period both in El Mirón and in the Cantabrian region, indicating a technological transition in preferred weaponry from foliate and shouldered points to microliths and antler sagaies between about 17,000-16,000 BP (uncalibrated), during the early part of the Oldest Dryas pollen zone. Now with 65 14C dates, El Mirón is one of the most thoroughly dated prehistoric sites in western Europe. The until-now poorly dated, but very distinctive Initial Cantabrian Magdalenian lithic artifact assemblages are briefly summarized.
    • Spatial Radiocarbon and Stable Carbon Isotope Variability of Mineral and Thermal Waters in Slovakia

      Povinec, P. P.; Franko, O.; Šivo, A.; Richtáriková, M.; Breier, R.; Aggarwal, P. K.; Araguás-Araguás, L. (Department of Geosciences, The University of Arizona, 2010-01-01)
      Isotope hydrology investigations were carried out with the aim to study isotope variability in mineral and thermal waters (MTW) of Slovakia. The aquifers of MTW were formed by Triassic limestones and dolomites, which are found in the mountains as well as in the pre-Tertiary substratum of depressions and lowlands. The MTW were of artesian and/or open structures. At present, there are only boreholes available, as natural outflows have already been captured by them. Large spatial isotope variability (14C between 2 and 33.6 pMC, 18O between -11.8 and -9.8, and 13C between -12.7 and -3.4 for bicarbonates and -21 and -4.9 for free CO2) and heterogeneity of MTW was observed, indicating different origins of MTW. Corrected radiocarbon apparent ages of MTW indicate that they mostly infiltrated during the Würm and Holocene periods.
    • Radiocarbon Dating of the Last Volcanic Eruptions of Ciomadul Volcano, Southeast Carpathians, Eastern-Central Europe

      Harangi, Sz; Molnár, M.; Vinkler, A. P.; Kiss, B.; Jull, A. J. T.; Leonard, A. G. (Department of Geosciences, The University of Arizona, 2010-01-01)
      This paper provides new accelerator mass spectrometry (AMS) radiocarbon age data for the last volcanic events in the Carpathian-Pannonian region of eastern-central Europe. The eruption ages were determined on charcoal fragments collected from pumiceous pyroclastic flow deposits at 2 localities of the Ciomadul Volcano. Two charcoal samples from the southeastern margin of the volcano (Bixad locality) set the date of the last volcanic eruption to 27,200 +/- 260 yr BP (29,500 +/- 260 cal BC). On the other hand, our data show that the Tusnad pyroclastic flow deposit, previously considered as representing the youngest volcanic rock of the region, erupted at ~39,000 yr BP (~41,300 cal BC). Thus, a period of dormancy more than 10,000 yr long might have elapsed between the 2 volcanic events. The different ages of the Tusnad and Bixad pyroclastic flow deposits are confirmed also by the geochemical data. The bulk pumices, groundmass glass, and the composition of the main mineral phases (plagioclase and amphibole) suggest eruption of slightly different magmas. Considering also the assumed long volcanic history (~600 ka) of the Ciomadul, these data suggest that further detailed studies are necessary on this seemingly inactive volcano in order to evaluate the possible renewal of volcanic activity in the future.
    • AMS 14C Dating of Human Bones Using Sequential Pyrolysis and Combustion of Collagen

      Wang, Hong; Ambrose, Stanley H.; Hedman, Kristin M.; Emerson, Thomas E. (Department of Geosciences, The University of Arizona, 2010-01-01)
      The Radiocarbon Dating Laboratory at the University of Illinois has been using the pyrolysis-combustion technique to separate pyrolysis-volatile (Py-V) or low molecular weight and pyrolysis-residue (Py-R) or high molecular weight compounds for 14C dating of organic remains since 2003. We have applied this method to human collagen dating to examine the 14C age difference between low and high molecular weight organic compounds. Results show that both fractions of late prehistoric period human bones from Illinois archaeological sites yield identical 14C dates but that Py-V or low molecular weight fractions of Archaic period human bones appear to be slightly contaminated. In this case, Py-V components or low molecular weight collagen fraction yield older 14C dates, which could result from contamination from old organic-rich sediments. The pyrolysis-combustion technique provides an economical alternative method to date bones that have not been satisfactorily dated using conventional purification techniques.
    • The Influences of Hydrology on the Radiogenic and Stable Carbon Isotope Composition of Cave Drip Water, Grotta di Ernesto (Italy)

      Fohlmeister, J.; Schröder-Ritzrau, A.; Spötl, C.; Frisia, S.; Miorandi, R.; Kromer, B.; Mangini, A. (Department of Geosciences, The University of Arizona, 2010-01-01)
      14C and 13C values of C-containing species in cave drip waters are mainly controlled by the C isotope composition of karst rock and soil air, as well as by soil carbon dynamics, in particular the amount of soil CO2 in the unsaturated soil zone and the process of calcite dissolution. Here, we investigate soil carbon dynamics by analyzing the 14C activity and 13C values of C dissolved in cave drip water. Monthly over a 2-yr period, we collected drip water from 2 drip sites, one fast and one relatively slow, within the shallow Grotta di Ernesto Cave (NE Italy). The 14C data reveal a pronounced annual cycle. In contrast, the 13C values do not show an annual pattern and only small interannual variability compared to the 13C values of soil waters. The annual 14C drip-water cycle is a function of drip-rate variability, soil moisture, and ultimately hydrology.
    • Refining Background Corrections for Radiocarbon Dating of Bone Collagen at ORAU

      Wood, R. E.; Bronk Ramsey, C.; Higham, T. F. G. (Department of Geosciences, The University of Arizona, 2010-01-01)
      During the laboratory pretreatment of samples for radiocarbon dating, small amounts of carbon may be added to a sample. Contamination can be incorporated at any stage: during chemical pretreatment, combustion to CO2, graphitization, or accelerator mass spectrometry (AMS) measurement. Such carbon contamination is often modern in age, and so can have an especially severe effect on samples older than ~25 ka BP. During the extraction of collagen from bone using the ultrafiltration protocol at the Oxford Radiocarbon Accelerator Unit (ORAU), small amounts of young carbon are added to the sample. Currently, this contamination is poorly characterized when less than 10 mg of collagen is extracted from a bone. Demand to date small collagen samples with 14C concentrations that approach the detection limit of AMS measurement has increased recently with the growing interest in, for example, directly dating Neanderthal remains and Upper Paleolithic bone artifacts. This paper aims to reduce the minimum collagen sample size required to produce a reliable date from 10 to 5 mg by re-examining the combustion background and subsequently the pretreatment background for bone. The average of 136 measurements of directly combusted nylon suggests that 0.0007 0.001 mg of modern carbon is added to each sample, although the distribution is positively skewed. Regression analysis of the measurements of 52 collagen samples extracted from a bone of background age results in a background of just less than 50,000 BP for bone treated at ORAU.
    • Report on the 20th International Radiocarbon Conference Graphitization Workshop

      Turnbull, Jocelyn; Prior, Christine (Department of Geosciences, The University of Arizona, 2010-01-01)
      A sample preparation workshop was convened at the 20th International Radiocarbon conference, with about 30-40 attendees. The term "sample preparation" was not further specified to allow participants to address the laboratory issues most important to them. Given the short time available, the focus quickly narrowed to details of graphite preparation for accelerator mass spectrometry (AMS), with particular interest in procedures for small samples, and hence we have changed the title to reflect the focus. Here, we summarize the workshop discussion, adding additional background information and references to publications. Several aspects of graphite preparation are included: catalyst types and ratio of catalyst to carbon; optimal reaction temperatures for various sample sizes; methods for water removal; types of pressure transducers; preconditioning of catalyst; and problems with blank values in very small samples. The pros and cons of sample dilution were also discussed.
    • Robust Bayesian Analysis, an Attempt to Improve Bayesian Sequencing

      Weninger, Franz; Steier, Peter; Kutschera, Walter; Wild, Eva Maria (Department of Geosciences, The University of Arizona, 2010-01-01)
      Bayesian sequencing of radiocarbon dates deals with the problem that in most cases there does not exist an unambiguous way to define the so-called prior function, which represents information in addition to the result of the 14C measurements alone. However, a random choice of a particular prior function can lead to biased results. In this paper, "robust Bayesian analysis," which uses a whole set of prior functions, is introduced as a more reliable method. The most important aspects of the mathematical foundation and of the practical realization of the method are described. As a general result, robust Bayesian analysis leads to higher accuracy, but paid for with reduced precision. Our investigations indicate that it seems possible to establish robust analysis for practical applications.
    • The Impact of Holocene Climate on the Development of Prehistoric Societies in Southern Siberia

      Kulkova, Marianna; Krasnienko, Sergey (Department of Geosciences, The University of Arizona, 2010-01-01)
      Geochemical data of 10Be, 14C, 18O obtained from natural archives (tree rings, ice sheets, varves, corals) indicates that the climate during the Holocene was not stable. The cosmogenic isotope fluctuations are bound by the periodicity on solar activity and climatic changes. The sharpest and most abrupt climatic deteriorations are registered in the Early and Middle Holocene at 8200, 5800, 5400, 4300, and 2800 cal BP. These events are characterized by cold conditions. The impact of climate on human communities in steppe depressions in southern Siberia (Nazarovo, Minusinsk, and Turano-Uyuk) was noticeable. The differences of local landscape-climatic conditions in these depressions were connected with global climatic changes to determine the processes of occupation, development, and migrations of ancient societies during the Neolithic, Bronze Age, and Iron Age. The chronology of archaeological cultures was also correlated with the local and global climatic changes during the Early and Middle Holocene in southern Siberia. Here, we generalize the literature data about Holocene climatic changes and archaeological cultures in the southern Siberia region.
    • Studies on the Preparation of Small 14C Samples with an RGA and 13C-Enriched Material

      Liebl, Jakob; Avalos Ortiz, Roswitha; Golser, Robin; Handle, Florian; Kutschera, Walter; Steier, Peter; Wild, Eva Maria (Department of Geosciences, The University of Arizona, 2010-01-01)
      The minimum size of radiocarbon samples for which reliable results can be obtained in an accelerator mass spectrometry (AMS) measurement is in many cases limited by carbon contamination introduced during sample preparation (i.e. all physical and chemical steps to which samples were subjected, starting from sampling). Efforts to reduce the sample size limit down to a few mu-g carbon require comprehensive systematic investigations to assess the amount of contamination and the process yields. We are introducing additional methods to speed up this process and to obtain more reliable results. A residual gas analyzer (RGA) is used to study combustion and graphitization reactions. We could optimize the reaction process at small CO2 pressures and identify detrimental side reactions. Knowing the composition of the residual gas in a graphitization process allows a reliable judgment on the completeness of the reaction. Further, we use isotopically enriched 13C (greater than or equal to 98% 13C) as a test material to determine contamination levels. This offers significant advantages: 1) The measurement of 12C/13C in CO2 is possible on-line with the RGA, which significantly reduces turnaround times compared to AMS measurements; 2) Both the reaction yield and the amount of contamination can be determined from a single test sample. The first applications of isotopically enriched 13C and the RGA have revealed that our prototype setup has room for improvements via better hardware; however, significant improvements of our sample processing procedures were achieved, eventually arriving at an overall contamination level of 0.12 to 0.15 mu-g C during sample preparation (i.e. freeze-drying, combustion, and graphitization) of mu-g-sized samples in aqueous solution, with above 50% yield.