• In Memoriam: Henry N. Michael (1912-2006)

      Department of Geosciences, The University of Arizona, 2006-01-01
    • Intrashell Radiocarbon Variability in Marine Mollusks

      Culleton, Brendan J.; Kennett, Douglas J.; Ingram, B. Lynn; Erlandson, Jon M.; Southon, John R. (Department of Geosciences, The University of Arizona, 2006-01-01)
      We demonstrate variable radiocarbon content within 2 historic (AD 1936) and 2 prehistoric (about 8200 BP and 3500 BP) Mytilus californianus shells from the Santa Barbara Channel region, California, USA. Historic specimens from the mainland coast exhibit a greater range of intrashell variability (i.e. 180-240 14C yr) than archaeological specimens from Daisy Cave on San Miguel Island (i.e. 120 14C yr in both shells). d13C and d18O profiles are in general agreement with the upwelling of deep ocean water depleted in 14C as a determinant of local marine reservoir correction (Delta-R) in the San Miguel Island samples. Upwelling cycles are difficult to identify in the mainland specimens, where intrashell variations in 14C content may be a complex product of oceanic mixing and periodic seasonal inputs of 14C-depeleted terrestrial runoff. Though the mechanisms controlling Delta-R at subannual to annual scales are not entirely clear, the fluctuations represent significant sources of random dating error in marine environments, particularly if a small section of shell is selected for accelerator mass spectrometry (AMS) dating. For maximum precision and accuracy in AMS dating of marine shells, we recommend that archaeologists, paleontologists, and 14C lab personnel average out these variations by sampling across multiple increments of growth.
    • Letter to the Editor

      Harbottle, Garman (Department of Geosciences, The University of Arizona, 2006-01-01)
    • Marine Radiocarbon Reservoir Ages in Scottish Coastal and Fjordic Waters

      Cage, Alix G.; Heinemeier, Jan; Austin, William E. N. (Department of Geosciences, The University of Arizona, 2006-01-01)
      High freshwater inputs into Scottish sea lochs (fjords) combined with the restricted exchange between sea loch basin water and coastal Atlantic water masses are likely to result in reduced regional marine radiocarbon reservoir ages (R[t]) in these environments. To test this hypothesis, historical, museum-archived shells, collected live on known dates prior to AD 1950 from coastal locations in NW Scotland, were 14C dated to provide a means of determining R(t) and hence the regional deviation (R) from the modeled global surface ocean reservoir age (R). The sea loch data, when combined with 14C dates from the Scottish west coast (Harkness 1983), yield a regional Delta-R value of 26 +/14 yr. The R of sea loch (fjordic) and coastal waters of NW Scotland are statistically different (at a confidence level >95%) from the Delta-R value of 17 +/14 yr reported for UK coastal waters (Reimer 2005; data after Harkness 1983) and are in good agreement with the coastal Delta-R value of 33 +/93 yr reported by Reimer et al. (2002). Therefore, it is recommended that a regional Delta-R correction of 26 +/14 yr should be applied to modern (i.e. Pre-bomb but not prehistoric) marine 14C dates from the NW coast of Scotland.
    • New AMS 14C Dates from the Early Upper Paleolithic Sequence of Raqefet Cave, Mount Carmel, Israel

      Lengyel, György; Boaretto, Elisabetta; Fabre, Laurent; Ronen, Avraham (Department of Geosciences, The University of Arizona, 2006-01-01)
      Raqefet Cave (35 degrees 04'21"N, 32 degrees 39'17"W) is situated in the southeastern side of Mount Carmel in Israel (Figure 1) on the left bank of wadi Raqefet (230 m asl), ~50 m above the wadi bed. It is 50 m long with an area of ~500 m2 (Figure 2). Eric Higgs of Cambridge University and Tamar Noy of the Israel Museum conducted excavations at the site between 1970 and 1972 (Higgs et al. 1975). New excavations at the cave began in 2004 (Lengyel et al. 2005). Studies on the lithic archaeological remains from the 1970-1972 stratigraphic units assign Late Mousterian or Middle to Upper Paleolithic transition (layers VIII-VI in squares B-G/18-23), indeterminate early Upper Paleolithic (layer IV in squares B-G/18-23), Levantine Aurignacian (layers IV, III, and II in squares B-G/18-23), indeterminate late Upper Paleolithic (layer II in area B-G/18-23), Late Kebaran (layer I in squares B-G/18-23), Geometric Kebaran (layer VII in squares J-M/24-28), Late Natufian (layers IV-VI in squares A-H/7-17), Neolithic (I-IV in squares J-M/24-28), and Bronze Age (pits in squares A-H/7-17 and B-G/18-23) occupations (Higgs et al.1975; Lengyel 2003, 2005; Lengyel and Bocquentin 2005; Lengyel et al. 2005; Noy and Higgs 1971; Sarel 2004; Ziffer 1978a,b).
    • Over 16,000 Years of Fire Frequency Determined from AMS Radiocarbon Dating of Soil Charcoal in an Alluvial Fan at Bear Flat, Northeastern British Columbia

      Jull, A. J. Timothy; Geertsema, Marten (Department of Geosciences, The University of Arizona, 2006-01-01)
      We present results of radiocarbon dating of charcoal from paleosols and buried charcoal horizons in a unique sequence, which potentially records the last 36,000 yr, from a fan at Bear Flat, British Columbia (BC) (56 degrees 16'51"N, 121 degrees 13'39"W). Evidence for forest-fire charcoal is found over the last 13,500 +/110 14C yr before present (BP) or 16,250 +/700 cal BP. The study area is located east of the Rocky Mountains in an area that was ice-free at least 13,970 +/170 14C yr BP (17,450-16,150 cal BP) ago. The latest evidence of fire is during the Medieval Warm Period (MWP). The charcoal ages show a periodicity in large fires on a millennial scale through the Holocene—an average of 4 fires per thousand years. Higher fire frequencies are observed between 2200 to 2800 cal BP, ~5500 and ~6000 cal BP, ~7500 to 8200 cal BP, and 9000 to 10,000 cal BP. These intervals also appear to be times of above-average aggradation of the fan. We conclude that fire frequency is related to large-scale climatic events on a millennial time scale.
    • Paleoproductivity Variations in the Equatorial Arabian Sea: Implications for East African and Indian Summer Rainfalls and the El Niño Frequency

      Tiwari, Manish; Ramesh, Rengaswamy; Bhushan, Ravi; Somayajulu, B. L. K.; Jull, A. J. Timothy; Burr, George S. (Department of Geosciences, The University of Arizona, 2006-01-01)
      We analyzed a sediment core from the equatorial Arabian Sea, chronologically constrained by accurate accelerator mass spectrometry (AMS) radiocarbon dates on selected planktonic foraminiferal species, for paleoproductivity variations corresponding to the variations in the Indian Ocean Equatorial Westerlies (IEW). The IEW in turn are positively correlated to the Southern Oscillation Index (SOI), which is a measure of El Nio, Southwest monsoon (SWM), and east African rainfall (EAR). The productivity data show that Indian and east African rainfalls declined from 35,000 calendar yr BP up to the last glacial maximum (LGM), with the maximum El Nio frequency during the last glacial period. From ~14,500 to ~2000 calendar yr BP (i.e. Core top), we find strengthening SWM and EAR along with declining El Nio frequency.
    • Quantitative Determination by 14C Analysis of the Biological Component in Fuels

      Dijs, Ivo J.; van der Windt, Eric; Kaihola, Lauri; van der Borg, Klaas (Department of Geosciences, The University of Arizona, 2006-01-01)
      Radiocarbon analysis was performed by liquid scintillation counting (LSC) and accelerator mass spectrometry (AMS) to assess whether the content of biological components in hydrocarbon fuels could be derived. Different fuel mixtures were prepared containing bioethanol, fossil ethanol, and fossil gasoline. The specific 14C activity of these mixtures was obtained from LSC measurements and directly related to the concentration of carbon originating from the bioethanol (biocarbon). The results were checked via standardized carbon dating procedures and AMS. A good linear correlation exists between the fuel mixtures specific 14C activity and the concentration of biocarbon. Also, the biocarbon fraction of the fuel mixture (the ratio biocarbon : total carbon) and the normalized fraction of biocarbon (%M) showed good linear correlation. Therefore, both relations provide a possibility to quantitatively determine a fuels biocarbon content by 14C analysis. When the sample composition is known (e.g. Resolved by gas chromatography-mass spectroscopy [GC-MS] and nuclear magnetic resonance [NMR]), the amount of particular biological components in a fuel sample can be derived subsequently. For mixtures of bioethanol, fossil ethanol, and gasoline with bioethanol contents in the range of 0.52% m/m, it was found that errors in the normalized fraction of biocarbon (%M) were in the range of 2510%, respectively. For samples with a higher bioethanol content (up to pure bioethanol), the errors in %M were 10%. Errors might be larger if substantial changes in the concentration of atmospheric 14C took place during the growth period of the biofuel feedstock. By taking into account the variation in specific 14C activity of carbon over the last decades, and by modeling simple tree-growth, it could be illustrated that this effect becomes significant only if the biofuel feedstock stopped growing more than 1 decade ago, e.g. With wood from constructions.
    • Radioactive Graphite Dispersion in the Environment in the Vicinity of the Chernobyl Nuclear Power Plant

      Buzinny, Michael (Department of Geosciences, The University of Arizona, 2006-01-01)
      This paper estimates the radioactive graphite dispersion on the land surface (forest litter and soil) as a result of the Chernobyl Nuclear Power Plant (NPP) release. Graphite mass was calculated using an estimated average concentration of 2.5 x 10^7 Bq/kg C (carbon). The sample collection method, sample origin and its mass, and sample preparation procedure used for preparation of benzene were taken into account to obtain the optimum sensitivity of the method. Thus, the sensitivity of the corresponding method for graphite detection in forest litter was estimated to be 0.2 mg/m2. All analyses gave a range of deposited graphite from 0.12 to 52.6 mg/m2. The maximum value was observed at a site located 9 km west of the Chernobyl NPP. The results of the study indicate the importance of studying the upper layer of soil (05 cm) in addition to the lower layer of forest litter.
    • Radiocarbon Chronology of Prehistoric Campsites in Alpine and Subalpine Zones at Haleakalā, Maui Island, USA

      Carson, Mike T.; Mintmier, Melanie A. (Department of Geosciences, The University of Arizona, 2006-01-01)
      A chronological synthesis of prehistoric campsites in alpine and subalpine zones (~2-3 km asl) at Haleakalā, Maui Island, USA, is based on relative stratigraphy from 24 test excavations, associated artifacts of known or probable time periods, and 12 radiocarbon dates. The results indicate intensive use of the unfavorable high-altitude environment in the range of AD 1400-1600, with very limited use slightly earlier. Numerous campsites were used repeatedly near the Haleakalā crater rim and scattered on the lower western mountain slope. Prior to this time, activity in this inhospitable setting was infrequent and occurred on a small scale.
    • Radiocarbon Dates from Neolithic and Bronze Age Hunter-Gatherer Cemeteries in the Cis-Baikal Region of Siberia

      Weber, Andrzej W.; Beukens, Roelf P.; Bazaliiskii, Vladimir I.; Goriunova, Olga I.; Savel'ev, Nikolai A. (Department of Geosciences, The University of Arizona, 2006-01-01)
      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).
    • Radiocarbon Dating and Balearic Prehistory: Reviewing the Periodization of the Prehistoric Sequence

      Mic, Rafael (Department of Geosciences, The University of Arizona, 2006-01-01)
      The Balearic Islands are one of the most widely dated regions in Europe, totaling about 800 dates. The aim of this paper is to propose an updated periodization for the prehistory of Majorca and Minorca based on the analysis of a series of absolute dates for over 100 archaeological sites and in combination with a critical assessment of the associated contextual information. Only by means of a solid chronological scheme will we then be able to approach research into the social significance of the vast archaeological record that the islands has to offer and also make reliable comparisons with developments in surrounding regions.
    • Radiocarbon Dating of Soil Organic Matter Fractions in Andosols in Northern Ecuador

      Tonneijck, Femke H.; van der Plicht, Johannes; Jansen, Boris; Verstraten, Jacobus M.; Hooghiemstra, Henry (Department of Geosciences, The University of Arizona, 2006-01-01)
      Volcanic ash soils (Andosols) may offer great opportunities for paleoecological studies, as suggested by their characteristic accumulation of organic matter (OM). However, understanding of the chronostratigraphy of soil organic matter (SOM) is required. Therefore, radiocarbon dating of SOM is necessary, but unfortunately not straightforward. Dating of fractions of SOM obtained by alkali-acid extraction is promising, but which fraction (humic acid or humin) renders the most accurate 14C dates is still subject to debate. To determine which fraction should be used for 14C dating of Andosols and to evaluate if the chronostratigraphy of SOM is suitable for paleoecological research, we measured 14C ages of both fractions and related calibrated ages to soil depth for Andosols in northern Ecuador. We compared the time frames covered by the Andosols with those of peat sequences nearby to provide independent evidence. Humic acid (HA) was significantly older than humin, except for the mineral soil samples just beneath a forest floor (organic horizons), where the opposite was true. In peat sections, 14C ages of HA and humin were equally accurate. In the soils, calibrated ages increased significantly with increasing depth. Age inversions and homogenization were not observed at the applied sampling distances. We conclude that in Andosols lacking a thick organic horizon, dating of HA renders the most accurate results, since humin was contaminated by roots. On the other hand, in mineral soil samples just beneath a forest floor, humin ages were more accurate because HA was then contaminated by younger HA illuviated from the organic horizons. Overall, the chronostratigraphy of SOM in the studied Andosols appears to be suitable for paleoecological research.
    • Radiocarbon Dating Sites of Itaparica Dam, São Francisco River Valley, Brazil

      de Andrade Lima, L. R. P. (Department of Geosciences, The University of Arizona, 2006-01-01)
      This paper reports radiocarbon dates of samples from archaeological sites in the Itaparica Dam region of the So Francisco River (Brazil). This region is important due to the evidence of its use by several prehistoric groups of huntergatherers. In the 1980s, a Brazilian state hydroelectric company (CHESF) engaged the federal universities of Bahia and Pernambuco to perform an archaeological rescue excavation at the Itaparica Dam reservoir area. This excavation allowed the collection of a large number of ceramics and lithic artifacts as well as fireplace charcoal. In this study, fireplace charcoal samples from the Bahia State riverside of the Itaparica Dam were selected and used for dating purposes. The 14C ages were between 3840 and 210 BP, and the values of d13C range from -22.93 to -24.81ppm. The 14C dates, in addition to the archaeological findings, indicate that the presence of humans in the region was contemporary with the intermediate levels of older sites found in the adjacent area, and also indicate different settlement periods.
    • Radiocarbon Determination of Particulate Organic Carbon in Non-Temperated, Alpine Glacier Ice

      Steier, Peter; Shah, Sunita R.; Drosg, Roswitha; Pearson, Ann; Fedi, Mariaelenea; Kutschera, Walter; Schock, Martin; Wagenbach, Dietmar; Wild, Eva Maria (Department of Geosciences, The University of Arizona, 2006-01-01)
      Dating ice samples from glaciers via radiocarbon is a challenge that requires systematic investigations. This work describes an approach for extraction and accelerator mass spectrometry (AMS) 14C analysis of the particulate organic carbon (POC) fraction in glacier ice samples. Measurements were performed at VERA (Vienna Environmental Research Accelerator) on ice samples obtained mainly from the non-temperated ablation zone of the Grenzgletscher (Grenz Glacier) system (Monte Rosa Massif, Swiss Alps). The samples were obtained from 2 sampling sites situated roughly on a common flow line. The sample masses used were between 0.3 and 1.4 kg of ice, yielding between 18 and 307 micrograms of carbon as POC. The carbon contamination introduced during sample processing varied between 5.4 and 33 micrograms C and originated mainly from the quartz filters and the rinsing liquids used in processing. Minimum sample sizes for successful graphitization of CO2 in our laboratory could be reduced to <10 micrograms carbon, with a background in the graphitization process of ~0.5 micrograms of 40-pMC carbon. Evaluation of the whole procedure via 11 Grenzgletscher samples revealed a surprisingly large scatter of pMC values. We obtain a mean calibrated age of 2100 BC to AD 900 (95.4% confidence level), which is not significantly different for the 2 sampling sites. Discussions of these results suggest that single 14C dates of glacial POC are presently of limited significance. Future improvements with respect to analytical precision and sample characterization are proposed in order to fully explore the POC dating potential.
    • Radiocarbon Laboratories

      Department of Geosciences, The University of Arizona, 2006-01-01
      This is Radiocarbon's annual list of active radiocarbon laboratories and personnel known to us. Conventional beta-counting facilities are listed in Part I, and accelerator mass spectrometry (AMS) facilities are listed in Part II. Laboratory code designations, used to identify published dates, are given to the left of the listing. (See p 515 for a complete list of past and present lab codes.)
    • Radiocarbon Laboratory at the National Autonomous University of Mexico: First Set of Samples and New 14C Internal Reference Material

      Beramendi-Orosco, Laura E.; Gonzalez-Hernandez, Galia; Urrutia-Fucugauchi, Jaime; Morton-Bermea, Ofelia (Department of Geosciences, The University of Arizona, 2006-01-01)
      This contribution reports the first set of samples and the creation of an internal reference material at the recently opened Radiocarbon Laboratory at the National Autonomous University of Mexico (UNAM). Samples for the initial measurements were selected from archaeological and dating projects on Teotihuacán, one of the largest and best-studied Mesoamerican urban and ceremonial centers. The 14C dates were compared to results obtained by 2 other laboratories in order to assess the results obtained at UNAM and validate the adopted methodology. As part of the quality assurance protocol, an internal reference material was created that consists of charred wood from the Teotihuacán site with a 14C activity in the value range expected for samples from Mesoamerican archaeological sites. Results from 7 analyses have a mean of 1750 +/16 BP (80.43 +/0.16 pMC).
    • Response to Beavan Athfield's “Comment on ‘Diet-Derived Variations in Radiocarbon and Stable Isotopes: A Case Study from Shag River Mouth, New Zealand’”

      Anderson, A.; Higham, Thomas (Department of Geosciences, The University of Arizona, 2006-01-01)
      Beavan Athfield (2006) has commented on our recent paper in this journal (Higham et al. 2005). In our opinion, both in her response and in Beavan Athfield (2004) she misrepresents the evidence and conclusions presented by Anderson (2000). She claims (Beavan Athfield 2006:117) that Andersons (2000) Figure 6, which is reproduced as Beavan Athfields (2004) Figure 1, shows that ages of ancient rat bone gelatin in 1995-1996 (NZA numbers 4000-6000) were exclusively earlier than about 1000 BP, while those from 1997 onward (NZA numbers 7000+) were exclusively later than about 1000 BP. Beavan Athfield asserts that this is the result of Anderson (2000) ignoring 9 published accelerator mass spectrometry (AMS) results from 1995-1996 that were younger than about 900 BP. These would be serious claims of poor scholarship, were they substantiated, but in fact, Anderson (2000, 2004) never asserted that the AMS results were distributed so exclusively, nor did he fail to take account of all published results.
    • Response to Moss et al. “An Early Holocene/Late Pleistocene Archaeological Site on the Oregon Coast? Comments on Hall et al. (2005)”

      Davis, Loren G.; Hall, Roberta A.; Willis, Samuel C. (Department of Geosciences, The University of Arizona, 2006-01-01)
      Moss et al. (2006) provided comments and criticisms of our recent paper in this journal (Hall et al. 2005). We can appreciate the need for promoting vigorous dialogue among those interested in the research of early sites along the New World Pacific Margin and thus welcome their intervention; however, we are compelled to respond because they raise several points that require clarification and introduce a critical error that must be corrected.
    • Seawater Radiocarbon Evolution in the Gulf of Alaska: 2002 Observations

      Guilderson, Thomas P.; Roark, E. Brendan; Quay, Paul D.; Flood Page, Sarah; Moy, Christopher (Department of Geosciences, The University of Arizona, 2006-01-01)
      Oceanic uptake and transport of bomb radiocarbon as 14CO2 created by atmospheric nuclear weapons testing in the 1950s and 1960s has been a useful diagnostic for determining the carbon transfer between the ocean and atmosphere. In addition, the distribution of 14C in the ocean can be used as a tracer of oceanic circulation. Results obtained on samples collected in the Gulf of Alaska in the summer of 2002 provide a direct comparison with results in the 1970s during GEOSECS and in the early 1990s during WOCE. The open gyre values are 20-40 lower than those documented in 1991 and 1993 (WOCE), although the general trends as a function of latitude are reproduced. Surface values are still significantly higher than pre-bomb levels (~-105 or lower). In the central gyre, we observe ∆14C values that are lower in comparison to GEOSECS (stn 218) and WOCE P16/P17 to a density of ~26.8 sigma-t. This observation is consistent with the overall decrease in surface ∆14C values and reflects the erosion of the bomb-14C transient. We propose that erosion of the bomb-14C transient is accomplished by entrainment of low-14C water via vertical exchange within the Gulf of Alaska and replenishment of surface and subthermocline waters with waters derived from the far northwest Pacific.