• 14C Dates and the Iron Age Chronology of Israel: A Response

      Mazar, Amihai; Bronk Ramsey, Christopher (Department of Geosciences, The University of Arizona, 2008-01-01)
      Boaretto et al. (2005) published 68 radiocarbon dates relating to 30 samples from 10 Iron Age sites in Israel as part of their Early Iron Age Dating Project. Though the main goal of their paper was an interlaboratory comparison, they also presented results of Bayesian models, calculating the transition from Iron Age I to Iron Age II in Israel to be about 900 BCE instead of the conventional date of about 1000 BCE. Since this date has great importance for all of Eastern Mediterranean archaeology, in this paper we examine the results in light of the dates published in the above-mentioned article. Our paper was revised in light of new data and interpretations published by Sharon et al. (2007). Following a survey of the contexts and specific results at each site, we present several Bayesian models. Model C2 suggests the date range of 961-942 BCE (68% probability) for the transition from Iron Age I to Iron Age II, while Model C3 indicates a somewhat later date of 948-919 BCE (compare the date 992-961 BCE calculated at Tel Rehov for the same transition). In our Model D, we calculated this transition date at Megiddo as taking place between 967-943 BCE. Finally, we calculated the range of dates of major destruction levels marking the end of the Iron Age I, with the following results: Megiddo VIA: 1010-943 BCE; Yoqne'am XVII: 1045-997 BCE; Tell Qasile X: 1039-979 BCE; Tel Hadar: 1043-979 BCE (all in the 68.2% probability range). Figure 4 indicates that the transition between Iron I and II probably occurred between these above-mentioned destruction events and the dates achieved in our Models C2 or C3, namely during the first half of the 10th century BCE. This study emphasizes the sensitivity of Bayesian models to outliers, and for reducing or adding dates from the models. This sensitivity should be taken into account when using Bayesian models for interpreting radiometric dates in relation to subtle chronological questions in historical periods.
    • 14C Dating of the Upper Paleolithic Site at Krems-Hundssteig in Lower Austria

      Wild, E. M.; Neugebauer-Maresch, C.; Einwögerer, T.; Stadler, P.; Steier, P.; Brock, F. (Department of Geosciences, The University of Arizona, 2008-01-01)
      The open-air archaeological site at Krems-Hundssteig is a well-known Upper Paleolithic site located in Lower Austria. The site was discovered in the late 19th/early 20th centuries when a large number of archaeological remains were collected during the course of loess quarrying. Although no systematic excavation has ever been performed, Krems-Hundssteig has been described since its discovery as typical of the Aurignacian period in this region based on the numerous archaeological finds; accordingly, the culture has been named Kremsien by some authors. Surprisingly, the artifacts found in a recent excavation adjacent to this location showed solely Gravettian features, calling into question the original assignment to the Aurignacian. Although the earlier assignment was supported by a radiocarbon date of ~35 kyr BP (Hahn 1977), new accelerator mass spectrometry (AMS) 14C dates proved that the recently excavated cultural layer originates from the Gravettian period. Older paleosols were also detected by sondage drillings at some depth below it. The new results indicate that a large Aurignacian level and a substantial complex of Gravettian layers are present in this area. Therefore, it must be assumed that more than 1 cultural level was affected and destroyed by the historic loess quarrying, and that the assemblage of Krems-Hundssteig artifacts, traditionally ascribed to the Aurignacian, might be interspersed with Gravettian pieces.
    • A New Chronology for Pololu Valley, Hawai'i Island: Occupational History and Agricultural Development

      Julie S. Field; Graves, Michael W. (Department of Geosciences, The University of Arizona, 2008-01-01)
      A reanalysis of the chronology of Pololu Valley, located in the district of Kohala on Hawai'i Island, is presented using standard radiocarbon and accelerator mass spectrometry (AMS) dating. Using curated materials from the 1970s, Pololu is reassessed and found to have the earliest coastal occupations in this part of Hawai'i, beginning about AD 1300. Occupations at the dunes and in the valley interior are investigated, as are dryland and wetland field agricultural systems. These data provide a refined model for expansion and intensification of agricultural production in the 15th-17th centuries, and link this remote valley to demographic and sociopolitical trends that were occurring in the rest of Hawai'i.
    • A New Method for Analyzing 14C of Methane in Ancient Air Extracted from Glacial Ice

      Petrenko, Vasilii V.; Smith, Andrew M.; Brailsford, Gordon; Riedel, Katja; Hua, Quan; Lowe, Dave; Severinghaus, Jeffrey P.; Levchenko, Vladimir; Bromley, Tony; Moss, Rowena; et al. (Department of Geosciences, The University of Arizona, 2008-01-01)
      We present a new method developed for measuring radiocarbon of methane (14CH4) in ancient air samples extracted from glacial ice and dating 11,000-15,000 calendar years before present. The small size (~20 g CH4 carbon), low CH4 concentrations ([CH4], 400-800 parts per billion [ppb]), high carbon monoxide concentrations ([CO]), and low 14C activity of the samples created unusually high risks of contamination by extraneous carbon. Up to 2500 ppb CO in the air samples was quantitatively removed using the Sofnocat reagent. 14C procedural blanks were greatly reduced through the construction of a new CH4 conversion line utilizing platinized quartz wool for CH4 combustion and the use of an ultra-high-purity iron catalyst for graphitization. The amount and 14C activity of extraneous carbon added in the new CH4 conversion line were determined to be 0.23-0.16 g and 23.57-16.22 pMC, respectively. The amount of modern (100 pMC) carbon added during the graphitization step has been reduced to 0.03 g. The overall procedural blank for all stages of sample handling was 0.75-0.38 pMC for ~20-g, 14C-free air samples with [CH4] of 500 ppb. Duration of the graphitization reactions for small (25 g C) samples was greatly reduced and reaction yields improved through more efficient water vapor trapping and the use of a new iron catalyst with higher surface area. 14C corrections for each step of sample handling have been determined. The resulting overall 14CH4 uncertainties for the ancient air samples are ~1.0 pMC.
    • Age Discrepancies with the Radiocarbon Dating of Sagebrush (Artemisia Tridentata Nutt.)

      Geib, Phil R. (Department of Geosciences, The University of Arizona, 2008-01-01)
      When ancient hearths at open archaeological sites do not yield carbonized annual plant remains or other high-quality samples, wood charcoal is commonly used for radiocarbon dating. Sagebrush (Artemisia tridentata Nutt.), a shrub frequently used for fuel across much of the western United States, seems a potentially better candidate for 14C dating than tree wood since the possibility for significant age discrepancy might be less. A comparison of multiple assays from single features reveals that sagebrush can overestimate age more than even tree wood charcoal. A plausible cause of this appears to be persistence of the shrub on the ground surface for an extended interval after death, such that use as fuel almost invariably occurs hundreds of years after fixation of carbon. The potential for age discrepancy may decrease as population density increases because the demand for fuel wood would have resulted in a more rapid turnover of the fuel biomass. This is not true for Archaic period foragers of western North America when population levels were likely quite low and residential mobility quite high.
    • AMS Dating on the Shell Bar Section from Qaidam Basin, NE Tibetan Plateau, China

      Zhang, H. C.; Fan, H. F.; Chang, F. Q.; Zhang, W. X.; Lei, G. L.; Yang, M. S.; Lei, Y. B.; Yang, L. Q. (Department of Geosciences, The University of Arizona, 2008-01-01)
      Radiocarbon dating by accelerator mass spectrometry (AMS) of the shell bar section of Qaidam Basin, NE Tibetan Plateau, shows that this section was formed between ~39.7 and ~17.5 14C kyr BP and represented the highest paleolake development period since the Late Pleistocene. It was difficult to obtain reliable dates due to the low organic carbon content, which was formed mainly by authochtonous algae-bacteria (Zhang et al. 2007a). In order to improve the dating, 14C ages of both the alkali residual and acid-soluble components of the organic carbon were measured to check the consistency of the dating results. Total organic carbon (TOC) content and stable carbon isotopes (delta-13Corg) might also be used as critical references for checking the reliability of dates. For example, in our study of the shell bar section from Qaidam Basin, we found that when the TOC content was higher than 0.15% and/or delta-13Corg was lower than -23‰, the AMS dates were reliable. AMS dating of fossil shells demonstrated that they could provide valuable age information. The ages given by fossil shells are comparable to those of bulk carbonate from a similar sampling site, and are about 15~18 kyr older than the ages given by organic matter. Due to the U/Th dating requirements and open nature of the system, we concluded that U/Th dating results are unreliable and that this technique is unsuitable for dating halite deposits from Qaidam Basin.
    • AMS Radiocarbon Dating of Giant Rock Scallop (Hinnites Multirugosus) Artifacts from San Miguel Island, California, USA

      Braje, Todd J.; Rick, Torben C.; Erlandson, Jon M. (Department of Geosciences, The University of Arizona, 2008-01-01)
      For at least 100,000 yr, marine shell beads have been important ornamental and symbolic artifacts intimately associated with the behavior of anatomically modern humans. In California, giant rock scallop (Hinnites multirugosus) beads were once thought to have been used only for the last 1000 yr, where they were considered to be markers of high social status among the Chumash Indians of the Santa Barbara Channel region. Direct accelerator mass spectrometry (AMS) radiocarbon dating of 1 giant rock scallop ornament and 2 beads from San Miguel Island extends the use of this shell for personal adornment to at least 8000 cal BP. Our study emphasizes the importance of direct AMS 14C dating of artifacts to enhance cultural chronologies and clarify the antiquity of various technologies and associated behaviors. Our results also caution archaeologists when equating artifact rarity with sociopolitical complexity.
    • AMS Radiocarbon Dating of Wood Samples from the Angkor Monuments, Cambodia

      Uchida, E.; Cunin, O.; Shimoda, I.; Takubo, Y.; Nakagawa, T. (Department of Geosciences, The University of Arizona, 2008-01-01)
      In the Angkor monuments of Cambodia, pieces of wood remain (as head frames of doorways, crossbeams, ceiling boards, etc.) in the following 8 monuments: Bakong, Lolei, Baksei Chamkrong, North Khleang, Angkor Wat, Banteay Kdei, Bayon, and Gates of Angkor Thom. Accelerator mass spectrometry (AMS) radiocarbon dating carried out on 15 wood samples collected from the above 8 monuments revealed that most of the wood samples are original, except for the head frame of a doorway in Baksei Chamkrong, the ceiling boards in the northwest tower, and a crossbeam with pivot hole in the southwest tower of the Inner Gallery of Angkor Wat. The 14C age for the head frame of a doorway in the inner wall under the central tower of North Khleang supports the hypothesis that the inner walls are additions from a later period.
    • Atmospheric 14C Variability Recorded in Tree Rings from Peninsular India: Implications for Fossil Fuel CO2 Emission and Atmospheric Transport

      Chakraborty, Supriyo; Dutta, Koushik; Bhattacharyya, Amalava; Nigam, Mohit; Schuur, Edward AG; Shah, Santosh K. (Department of Geosciences, The University of Arizona, 2008-01-01)
      Radiocarbon analysis in annual rings of a teak tree (Tectona grandis) is reported in comparison with previously published results. Samples (disks) were collected from Hoshangabad (22 degrees 30'N, 78 degrees E), Madhya Pradesh, in central India. The previously published sample was collected from Thane (19 degrees 12'N, 73 degrees E), Maharashtra, near the west coast of India (Chakraborty et al. 1994). Two short 14C time series were reconstructed with these tree samples to capture the bomb peak of atmospheric 14C and the spatial variability in this record. These time series represent the periods 1954-1977 and 1959-1980 for Hoshangabad and Thane, respectively. The 14C peaks in these places appear around 1964-1965. The Hoshangabad tree records a peak delta-14C value of 708 +/- 8‰, which conforms to the peak value of Northern Hemisphere Zone 3 as described in Hua and Barbetti (2004). But the peak 14C at Thane is somewhat less (630 +/- 8‰) probably due to the dilution by fossil fuel CO2 free of 14C emanating from the neighboring industrial areas. This depletion of peak values has been used to estimate the local emission of fossil fuel CO2, which is approximately 2.3% of the background atmospheric CO2 concentration.
    • Bayesian Refinement of a Stratified Sequence of Radiometric Dates from Punta de Chimino, Guatemala

      Bachand, Bruce R. (Department of Geosciences, The University of Arizona, 2008-01-01)
      Bayesian analysis of 6 radiocarbon and 2 luminescence determinations from Punta de Chiminos acropolis provides subcentury chronometric accuracy for a Protoclassic hiatus and a more decisive, incipient Early Classic abandonment. For the latter event, sensitivity tests and a redundant modal value pattern reduce the period of historical interest from a few centuries to several decades. The findings aid in selecting between 2 historical scenarios and demonstrate that improved chronological accuracy is attainable for sites and contexts lacking calendrical dates.
    • Calendar Age of Lisakovsky Timbers Attributed to Andronovo Community of Bronze Age in Eurasia

      Panyushkina, Irina P.; Mills, Barbara J.; Usmanova, Emma R.; Cheng, Li (Department of Geosciences, The University of Arizona, 2008-01-01)
      We measured radiocarbon ages of 22 decadal replications and 1 bulk group from 5 tree-ring specimens using acid-base-acid pretreatment and accelerator mass spectrometry (AMS). The study has the goal of refining the precision and resolution of a segment of the conventional Bronze Age chronology in the Eurasian steppe attributed to the multicultural community known as Andronovo. The archaeological timbers were gathered from 3 cemeteries at the Lisakovsky cluster of sites in Kazakhstan, where there is a prominent Andronovo occurrence that appears to show evidence of overlapping Alakul and Fedorovo cultures in the southern margin of the Eurasian steppe. The new set of Andronovo calendar dates derived from 14C wiggles and a composite floating tree-ring chronology places the cultural overlap from 1780 to 1660 cal BC. Results indicate older ages of artifacts from the Lisakovsky site than were previously determined by the typological chronology, shifting them from the Late Bronze Age to also include the transition between the Middle and Late Bronze Age. The chronological order of the Lisakovsky cemeteries provides strong evidence of contemporaneity of the Alakul and Fedorovo cultures in the Tobol River Valley for a portion of the 120-yr period of occupation. We discuss an application of the dated Alakul-Fedorovo overlap to the relationship and origin of different groups of the Andronovo community in the Ural region. Our results demonstrate the substantial power that tree rings from Bronze Age timbers provide for developing a precise and highly resolved calendar chronology of prehistoric human occupation in the Eurasian steppe during the 2nd millennium BC.
    • Comparison of Radiocarbon Ages from Different Organic Fractions in Tropical Peat Cores: Insights from Kalimantan, Indonesia

      Wüst, Raphael A. J.; Jacobsen, Geraldine E.; van der Gaast, Haitse; Smith, Andrew M. (Department of Geosciences, The University of Arizona, 2008-01-01)
      Various organic fractions of an Indonesian tropical peat deposit were dated using radiocarbon accelerator mass spectrometry (AMS). Four different depth layers, deposited during the last 28,000 14C yr, were analyzed and the data compared to bulk sample analyses. The pollen extracts consistently produced the oldest dates. The bulk samples (<250 mu-m and <100 mu-m) often yielded the youngest dates. The age difference between the individual fractions depended on the layer depth and hence the true age of the sampled peats. The age discrepancy was highest (~16,000 14C yr) in the oldest peat material. We interpret this to be a consequence of the input of organic matter over a long period of time, with peat oxidation and/or no peat accumulation during the last glacial maximum (LGM). The age discrepancies were smaller (between 10 and 900 14C yr) for the Holocene peat samples. It was concluded that the pollen extract fraction might be the most reliable fraction for dating tropical peat deposits that are covered by deeply rooting vegetation.
    • Comparisons and Interpretations of Charcoal and Organic Matter Radiocarbon Ages from Buried Soils in North-Central Colorado, USA

      Mayer, James H.; Burr, George S.; Holliday, Vance T. (Department of Geosciences, The University of Arizona, 2008-01-01)
      The reliability of radiocarbon ages based on soil organic matter (SOM) from Holocene buried soils in Middle Park, Colorado, is assessed by comparison with ages of charcoal. On average, 14C ages of SOM from buried surface horizons are 880 +/- 230 14C yr younger than charcoal ages from the same horizon. Humic acid (HA) and low-temperature (400 degrees C) combustion residue (LT) fractions are 390 +/- 230 and 1290 +/- 230 14C yr younger than charcoal ages, respectively, and HA ages are on average 860 +/- 140 14C yr older than LT fractions. We interpret the offsets between 14C ages of charcoal and SOM fractions and the consistent offsets between the HA and LT fractions to reflect the duration of pedogenesis and different residence times of the SOM fractions examined here. The stratigraphic coherence of charcoal 14C ages suggests short residence time on the landscape, with little subsequent reworking. 14C ages of HA and LT fractions are complimentary to charcoal, and HA ages are interpreted to represent minimum ages for the onset of pedogenesis and LT ages are considered maximum ages for burial. The 14C chronology from buried soils indicates an episode of hillslope erosion in Middle Park during the early Holocene, followed by a long period of land surface stability and soil formation between 9000-4500 BP. Two episodes of late Holocene hillslope erosion between 3500-2500 and 1000-500 BP correspond with warming recognized in the Colorado Front Range, while surface stability and soil formation between 2500-1000 BP is contemporaneous with evidence for cooling at higher elevations.
    • Contents

      Department of Geosciences, The University of Arizona, 2008-01-01
    • Contents

      Department of Geosciences, The University of Arizona, 2008-01-01
    • Contents

      Department of Geosciences, The University of Arizona, 2008-01-01
    • Development of Sample Pretreatment of Silk for Radiocarbon Dating

      Kim, Kyeong Ja; Southon, John; Imamura, Mineo; Sparks, Rodger (Department of Geosciences, The University of Arizona, 2008-01-01)
      We have developed sample pretreatments for silk for radiocarbon dating. Characteristics of silk under different types of pretreatment were investigated, as well as the behavior of dye and possible contaminants. We found that dye could be removed completely, together with all other foreign materials bigger than 1.2 m, using a glass microfiber filter after decomposition with 6N HCl. The decomposed proteins were concentrated using Centriprep ultrafiltration concentrators with 3 different molecular weight cut-offs. By taking a molecular weight fractionwhich selects for secondary structures of silk protein14C dating of silk samples can be made more reliable. This study confirms that uniformly fractured polypeptide chains of silk provide an appropriate fraction for 14C age dating to select silk protein against dye particles and undecomposed foreign contaminants.
    • Editorial Board

      Department of Geosciences, The University of Arizona, 2008-01-01