• 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.
    • 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.
    • AMS Radiocarbon Dates from Pleistocene and Holocene Mammals Housed in the New York State Museum, Albany, New York, USA

      Feranec, Robert S.; Kozlowski, Andrew L. (Department of Geosciences, The University of Arizona, 2010-01-01)
    • Carbon Isotope Measurements of Surface Seawater from a Time-Series Site off Southern California

      Hinger, Elise N.; Santos, Guaciara M.; Druffel, Ellen R. M.; Griffin, Sheila (Department of Geosciences, The University of Arizona, 2010-01-01)
      We report carbon isotope abundances of dissolved inorganic carbon (DIC) in surface seawater collected from a time-series site off the Newport Beach Pier in Orange County, California. These data represent the first time series of ∆14C data for a coastal southern California site. From a suite of samples collected daily from 16 October to 11 November 2004, ∆14C values averaged 32.1 +/- 4.4. Freshwater input from the Santa Ana River to our site caused ∆14C and 13C values to decrease. Since this initial set of measurements, a time-series site has been maintained from November 2004 to the present. Surface seawater has been collected bimonthly and analyzed for ∆14C, delta-13C, salinity, and sigma-CO2 concentrations. Water samples from the Santa Ana River were collected during the wet season. California sea mussels and barnacle shells, ranging from 4 to 6 months old, were also collected and analyzed. Results from May 2005 to January 2008 show no long-term changes in delta-13C DIC values. ∆14C DIC values over the 2005-2006 period averaged 33.7; high ∆14C values were observed sporadically (every 6-7 months), suggesting the presence of open water eddies at our site. Finally, in 2007, a stronger upwelling signal was apparent as indicated by correlations between ∆14C, salinity, and the Bakun index, suggesting that the ∆14C record is an indicator of upwelling in the Southern California Bight.
    • Current Pretreatment Methods for AMS Radiocarbon Dating at the Oxford Radiocarbon Accelerator Unit (ORAU)

      Brock, Fiona; Higham, Thomas; Ditchfield, Peter; Bronk Ramsey, Christopher (Department of Geosciences, The University of Arizona, 2010-01-01)
      In this paper, we summarize the main chemical pretreatment protocols currently used for AMS radiocarbon dating at the Oxford Radiocarbon Accelerator Unit, updating the protocols last described by Hedges et al. (1989).
    • Dating Human Occupation on Diatom-Phytolith-Rich Sediment: Case Studies of Mustang Spring and Lubbock Lake, Texas, USA

      Hatté, Christine; Hodgins, Gregory; Holliday, Vance T.; Jull, A. J. Timothy (Department of Geosciences, The University of Arizona, 2010-01-01)
      The Great Plains of North America have a rich archaeological record that spans the period from Late Glacial to Historic times, a period that also witnessed significant changes in climate and ecology. Chronometric dating of archaeological sites in many areas of the Great Plains, however, is often problematic, largely because charcoal and wood--the preferred materials for radiocarbon dating--are scarce in this grassland environment with few trees. Two reference archaeological sites are studied here: Mustang Spring and Lubbock Lake, Texas, USA. We carry out a geochronological approach based on a cross-study of carbon-derived data: combustion yield, 13C, 14C age differences between high temperature and low temperature released carbon, and the 14C age itself. A study that incorporates multiple approaches is required to solve issues induced by the sedimentological context, which is rich in both freshwater diatoms and phytoliths from quite different origins. Analysis of carbon-derived data allows us to draw a succession model of dry and wet episodes and to associate it with a chronological framework. In this way, we can assert that, for the Mustang Spring site, several human occupations existed from ~11 kyr BP to ~8.7 kyr BP along the 110-cm-long series with an interruption of ~150 yr that is associated with a palustrine environment between the Plainview and Firstview occupations.
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      Department of Geosciences, The University of Arizona, 2010-01-01
    • Holocene Variations of Radiocarbon Reservoir Ages in a Mediterranean Lagoonal System

      Sabatier, P.; Dezileau, L.; Blanchemanche, P.; Siani, G.; Condomines, M.; Bentaleb, I.; Piquès, G. (Department of Geosciences, The University of Arizona, 2010-01-01)
      To obtain a precise radiocarbon Holocene chronology in coastal areas, it is necessary to estimate the modern 14C reservoir age R(t) and its possible variations with time in relation to paleoenvironmental changes. The modern reservoir 14C age was estimated by comparing AMS 14C ages of 2 recent mollusk shells found in sediment cores sampled in the Palavasian lagoonal system (south of France) with ages derived from 210Pb and 137Cs data and historical accounts of identifiable storm events. The calculated modern R(t) value of 943 +/- 25 14C yr is about 600 yr higher than the global mean sea surface reservoir age. This high value, probably due to the relative isolation of the lagoon from marine inputs, is in good agreement with other R(t) estimates in Mediterranean lagoonal systems (Zoppi et al. 2001; Sabatier et al. 2008). 14C ages were also obtained on a series of Holocene mollusk shells sampled at different depths of the ~8-m-long core PB06. Careful examination of the 14C ages versus depth relationships suggests that R(t) in the past was lower and similar to the value presently measured in the Gulf of Lion (618 +/- 30 14C yr, Siani et al. 2000). The change in R(t) from 618 to 943 yr is thought to result from final closure of the coastal lagoon by the sandy barrier, due to the along-shore sediment transfer.
    • Radiocarbon AMS Data Analysis: From Measured Isotopic Ratios to 14C Concentrations

      Zoppi, Ugo (Department of Geosciences, The University of Arizona, 2010-01-01)
      Radiocarbon accelerator mass spectrometry (AMS) measurements are always carried out relative to internationally accepted standards with known 14C activities. The determination of accurate 14C concentrations relies on the fact that standards and unknown samples must be measured under the same conditions. When this is not the case, data reduction is either performed by splitting the collected data set into subsets with consistent measurement conditions or by applying correction factors. This paper introduces a mathematical framework that exploits the intrinsic variability of an AMS system by combining arbitrary measurement parameters into a normalization function. This novel approach allows the en-masse reduction of large data sets by providing individual normalization factors for each data point. Both general features and practicalities necessary for its efficient application are discussed.
    • Radiocarbon and Stable Carbon Isotope Analyses of Land Snails from the Chinese Loess Plateau: Environmental and Chronological Implications

      Xu, Bing; Gu, Zhaoyan; Han, Jingtai; Liu, Zongxiu; Pei, Yunpeng; Lu, Yanwu; Wu, Naiqin; Chen, Yongfu (Department of Geosciences, The University of Arizona, 2010-01-01)
      Paired radiocarbon and stable carbon analyses have been carried out on aragonite shells and organic soft bodies of snails from the Chinese Loess Plateau in order to explore the possibility of using these kinds of samples as environmental and chronological indicators. Results show that the soft bodies exhibit 14C concentrations similar to those of plant leaves, indicating that carbon in the soft bodies is fixed from organic diets. The aragonite shells are depleted in 14C compared to the soft bodies due to ingestion of 14C-depleted carbonate. This depletion shows a consistent pattern across the Chinese Loess Plateau, implying a good potential for the snail shells to be applicable for 14C dating with a simple correction. The 13C values measured for aragonite shells display a linear relationship with those obtained for the soft bodies with a constant offset. In addition, the carbon derived from organic diets accounts for more than 70% of the total shell carbon. This fact suggests that stable carbon isotope composition of aragonite shells mainly reflects that of organic diet, and could be used as a reliable indicator of paleodiet in the Chinese Loess Plateau.
    • Radiocarbon Dating of the Amphipolis Bridge in Northern Greece, Maintained and Functioned for 2500 Years

      Maniatis, Y.; Malamidou, D.; Koukouli-Chryssanthaki, H.; Facorellis, Y. (Department of Geosciences, The University of Arizona, 2010-01-01)
      The remains of a wooden construction, recovered in the 1970s at the northwest sector of the walls of the ancient city of Amphipolis (northern Greece), have been recognized as foundation remains of a wooden bridge described by Thucydides in his description of the events that took place at Amphipolis in 424-422 BC, during the Peloponnesian War. Frequent repairs in the Roman, Byzantine, and even Ottoman periods are very probable. In the last 10 yr, conservation has been done to enhance this unique monument. This work involves systematic investigation with radiocarbon dating of all the verified or suspected phases of this wooden bridge. The dating results reveal the beginning of construction most probably in the Archaic period and confirm beyond a doubt that the major construction phase took place in Classical times. Successive phases, related to repairs rather than to major reconstructions, have been detected during the Hellenistic, Roman, Early Christian, and Byzantine periods as well as the Ottoman era. The combined archaeometric and archaeological evidence leads to the remarkable conclusion that this bridge was functioning for about 2500 yr.
    • Radiocarbon Results from the Iron IIa Site of Atar Haroa in the Negev Highlands and Their Archaeological and Historical Implications

      Boaretto, E.; Finkelstein, I.; Shahack-Gross, R. (Department of Geosciences, The University of Arizona, 2010-01-01)
      In this article, we present a set of radiocarbon measurements from Atar Haroa, a site that belongs to the early Iron IIA Negev Highlands settlement system in southern Israel. The results place activity at the site in the 9th century BCE, with a possibility that it was founded in the 10th century BCE, probably in the second half. The Atar Haroa measurements seem to indicate that the early Iron IIA phase in the ceramic typology of Israel lasted until the mid-9th century BCE--somewhat later than previously suggested. These new data shed light on several issues related to the history of southern Israel in the late 10th and 9th centuries BCE.
    • Reconstruction of 130-kyr Relative Geomagnetic Intensities from 10Be in Two Chinese Loess Sections

      Zhou, Weijian; Xian, Feng; Beck, Warren; Jull, A. J. Timothy; An, Zhisheng; Wu, Zhenkun; Liu, Min; Chen, Maobai; Priller, Alfred; Kutschera, Walter; et al. (Department of Geosciences, The University of Arizona, 2010-01-01)
      Efforts to extract weak geomagnetic excursion signals from Chinese loess-paleosol 10Be have generally been unsuccessful due to the complexities of its accumulation, because the geomagnetic and climate (precipitation and dust) signals contained in loess-paleosol sequence are tightly overprinted. Here, we present a reconstruction of geomagnetic relative paleointensities for the past 130 kyr from 10Be records in 2 Chinese loess-paleosol sections using a correction based on the correlation of 10Be with magnetic susceptibility (SUS) to remove the climatic contamination. Both these records reveal the Laschamp and Blake events, which lie in the loess and paleosol (L1SS1 and S1SS3) horizons corresponding to mid-MIS 3 and 5e, respectively. The good agreement between our results and other geomagnetic intensities reconstructions from Atlantic and Pacific sediments indicates that our method is robust. Our study suggests the potential application of loess-paleosol 10Be for reconstructing geomagnetic intensity variations spanning the whole Quaternary.
    • Successful AMS 14C Dating of Non-Hydraulic Lime Mortars from the Medieval Churches of the Åland Islands, Finland

      Heinemeier, Jan; Ringbom, Åsa; Lindroos, Alf; Sveinbjörnsdóttir, Árný E. (Department of Geosciences, The University of Arizona, 2010-01-01)
      Fifteen years of research on accelerator mass spectrometry (AMS) radiocarbon dating of non-hydraulic mortar has now led to the establishment of a chronology for the medieval stone churches of the land Islands (Finland), where no contemporary written records could shed light on the first building phases. In contrast to other material for dating, well-preserved mortar is abundantly available from every building stage. We have gathered experience from AMS dating of 150 land mortar samples. Approximately half of them have age control from dendrochronology or from 14C analysis of wooden fragments in direct contact with the mortar. Of the samples with age control, 95% of the results agree with the age of the wood. The age control from dendrochronology, petrologic microscopy, chemical testing of the mortars, and mathematical modeling of their behavior during dissolution in acid have helped us to define criteria of reliability to interpret the 14C results when mortar dating is the only possibility to constrain the buildings in time. With these criteria, 80% of all samples reached conclusive results, and we have thus far been able to establish the chronology of 12 out of the 14 churches and chapels, while 2 still require complementary analyses.
    • Table of Contents

      Department of Geosciences, The University of Arizona, 2010-01-01
    • 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 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.
    • 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.