• Radiocarbon Dating of the Human Occupation of Australia Prior to 40 ka BP: Successes and Pitfalls

      Fifield, L. K.; Bird, M. I.; Turney, C. S. M.; Hausladen, P. A.; Santos, G. M.; di Tada, M. L. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Charcoal samples from ancient human occupation sites in Australia have been subjected to a rigorous pretreatment and stepped combustion regime in order to explore the possibility that these sites may be older than previous radiocarbon dating had suggested. In one case, the Devil's Lair site in southwest Australia, the methodology has clearly removed vestiges of contamination by more modern carbon and has led to a revised radiocarbon chronology that provides evidence for human occupation of southwest Australia by at least 44 ka BP and probably by 46-47 ka BP. In contrast, charcoal from the Nauwalabila site has been so severely altered that insufficient of the original carbon remains for reliable 14C dating. Finally, where the charcoal is well preserved, such as at the Carpenter's Gap site, the new results provide reassurance that earlier 14C results of approximately 40 ka BP are indeed true ages and are not simply at the limit of the 14C technique.
    • Radiocarbon Dating of Total Soil Organic Matter and Humin Fraction and its Comparison with 14C Ages of Fossil Charcoal

      Pessenda, L. C. R.; Gouveia, S. E. M.; Aravena, R. (Department of Geosciences, The University of Arizona, 2001-01-01)
      During the last decade radiocarbon dating has been used extensively in distinct regions of Brazil to provide information about soil chronology in paleoenvironmental studies. This paper presents 14C dating of soil organic matter (SOM), humin fraction, and charcoal in several soil profiles under natural vegetation from different Brazil locations (north, central, and southeast regions). The main objective is to compare the obtained 14C dating of total SOM with humin, the oldest fraction of SOM. In order to validate the humin ages these data are compared with the age of charcoal collected at similar depths. The 14C ages obtained on charcoal were, in most of the cases, in agreement with the humin fraction considering the experimental errors, or 20% older in average. The dates obtained from total SOM showed significantly younger ages than the humin fraction indicating contamination by younger carbon. These results show the humin fraction is considered a reliable material for 14C dating in soils. However, the humin fraction ages could be assumed as the minimum ages for carbon in soils.
    • Radiocarbon in Seawater at Radioactive Waste Dumping Sites in the Northeast Atlantic and Northwest Pacific

      Povinec, P. P.; Jull, A. J. T.; Burr, G. S. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Radiocarbon has been an important constituent of radioactive wastes dumped in the open ocean and marginal seas as well as wastes released from nuclear reprocessing plants. Therefore, in some regions these sources could have a greater impact on 14C concentration in seawater than global fallout. The high analytical sensitivity of 14C measurement by accelerator mass spectrometry (AMS) allows even tracer amounts of 14C to be found in seawater at radioactive waste dumping sites and their comparison with the global distribution of this radionuclide. Data on measurements of 14C in samples taken at former dumping sites in the northeast Atlantic and northwest Pacific Oceans and in the open ocean are discussed and compared with other anthropogenic radionuclides, namely 3H. Small increases in 14C concentrations observed in some bottom and surface seawater samples collected at the Northwest Pacific Ocean dumping sites require further 14C analyses before final conclusions can be made on possible leakages from dumped radioactive wastes.
    • Radiocarbon in Seawater Intruding into the Israeli Mediterranean Coastal Aquifer

      Yechieli, Yoseph; Sivan, Orit; Lazar, Boaz; Vengosh, A.; Ronen, D.; Herut, Barak (Department of Geosciences, The University of Arizona, 2001-01-01)
      Saline groundwaters from the Israeli coastal aquifer were analyzed for their radiocarbon and tritium content to assess the rate of seawater penetration. The low 14C values (28-88 pMC versus 100-117 pMC in seawater) imply an apparent non-recent seawater source, or water-rock interactions along the penetration route. The latter process is supported by measurable tritium values at some locations, which imply a relatively rapid rate of seawater intrusion. In other locations, low tritium values (<2 T.U.) indicate that recent seawater (<50 yr) did not penetrate inland. The low delta-13C values in saline groundwater (average of -5.3 per mil versus 0 per mil in seawater) indicate that the dissolved carbon pool is comprised of a significant fraction of organic carbon. A linear negative correlation between delta-13C and 14C implies that this organic source is old (low 14C values).
    • Radiocarbon Studies of Peat Bogs: An Investigation of South Kamchatka Volcanoes and Upper Volga Archaeological Sites

      Zaretskaia, N. E.; Ponomareva, V. V.; Sulerzhitsky, L. D.; Zhilin, M. G. (Department of Geosciences, The University of Arizona, 2001-01-01)
      We have undertaken extensive programs of natural radiocarbon measurement to date the evidence for various events buried in peat bogs. Two case studies are described here: 1) the chronological reconstruction of South Kamchatka volcanic eruptions and, 2) investigation of multi-layered archeological sites in the Upper Volga River Basin. Studies of sample composition and peat taphonomy allowed us to determine the source of 14C age deviations and to reconstruct the environmental history of organic matter accumulation. Data sets, obtained from different types of peat bog and containing traces of these Holocene events, are discussed.
    • Spatial Variations of Radiocarbon in the Coastal Aquifer of Israel—Indicators of Open and Closed Systems

      Bruce, Debbie; Friedman, Gerald M.; Kaufman, Aaron; Yechieli, Yoseph (Department of Geosciences, The University of Arizona, 2001-01-01)
      The spatial variation in radiocarbon concentration was studied in the Coastal Aquifer of Israel. Lower concentrations were found in the western section of the aquifer (55-70 pMC) as compared to the eastern section (80-100 pMC). Since no correlation was found between the tritium and radiocarbon values, these variations could not simply be explained by a difference in ages, or by a difference in the degree of old calcite dissolution as similar delta-13C values were found throughout the aquifer. The results are best explained when viewing the differences in 14C values within the same coastal aquifer, where the eastern section of the aquifer is a more open system and the western section is a more closed system. In general, the age of the groundwater in the coastal aquifer was found to be less than 50 years old (14C>55 and measurable tritium).
    • The Age of Upper Paleolithic Sites in the Middle Dnieper River Basin of Eastern Europe

      Abramova, Z. A.; Grigorieva, G. V.; Zaitseva, G. I. (Department of Geosciences, The University of Arizona, 2001-01-01)
      This paper discusses the comparative chronology of Upper Paleolithic sites in the Middle Dnieper River basin, based on archaeological and radiocarbon evidence. Three chronological periods of the development of the Upper Paleolithic are distinguished in this area. According to the data obtained, the third period is similar to the European Magdalenian, yet its economies were different. The base of the subsistence economy for Dnieperian hunters was the procurement of mammoth, while reindeer was the most important for the subsistence of European Magdalenian. The abundance of mammoths and the raw material in the form of mammoth tusks made a deep impact on both the economy and material culture of the hunters in the Dnieper River basin. The 14C dates confirm the chronological subdivision.
    • The Cave of Theopetra, Kalambaka: Radiocarbon Evidence for 50,000 Years of Human Presence

      Facorellis, Yorgos; Kyparissi, Apostolika Nina; Maniatis, Yannis (Department of Geosciences, The University of Arizona, 2001-01-01)
      The cave of Theopetra is located on the northeast side of a limestone rock formation, 3 km south of Kalambaka (21 degrees 40'46"E, 39 degrees 40'51"N), in Thessaly, central Greece. It is a unique prehistoric site for Greece, as the Middle and Upper Paleolithic, Mesolithic, and Neolithic periods are present here, bridging the Pleistocene with the Holocene. Several alternations of the climate during the Pleistocene are recognized in its stratigraphy. Among the most striking finds, two human skeletons, one from the Upper Paleolithic period after the Last Glacial Maximum and one from the Mesolithic period, should be emphasized, while in a deep Middle Paleolithic layer, the oldest human footprints, with remains of fire, were uncovered. During the 13 years of excavation, evidence of human activity suitable for radiocarbon dating was collected, such as charcoal samples from hearths and bones from the two human skeletons. The use of proportional counters for the measurement of 14C in combination with the recent improvement of the calibration curve has enabled the production of high-precision reliable ages Sixty 14C-dated samples, originating from 19 pits and from depths ranging from 0.10 m to 4.20 m, have already provided an absolute time framework for the use of the cave. The earliest limit of human presence probably exceeds 48,000 BP and the latest reaches World War II. Within these limits the 14C dating of samples from consecutive layers, in combination with the archaeological data, permits the resolution of successive anthropogenic and environmental events.
    • The Copper Age in Northern Italy

      Zoppi, U.; Fulcheri, E.; Gambari, F. M.; Hua, Q.; Lawson, E. M.; Micheletti Cremasco, M.; Venturino Gambari, M. (Department of Geosciences, The University of Arizona, 2001-01-01)
      During the period between the IVth and IIIrd millennia BC, profound changes for the ancient populations inhabiting the northern region of Italy occurred. The first Indo-European migrations were altering the ethnographic characteristics and, with the production of the first copper artifacts, the Neolithic Age was drawing to an end. The most significant testimony of that dramatic period is unquestionably the Otztal iceman. In addition, many other valuable archaeological sites, such as Alba (Cuneo, Italy), have been discovered. Although Alba produced the oldest evidence of copper objects in a Neolithic context (5380 +/40 BP; GX-25859-AMS), more recent discoveries have underlined the importance of this archaeological site. In this paper we will report on a series of radiocarbon measurements of bone remnants which, combined with morphologic, stratigraphic, paleoanthropologic, and paleopathologic studies, have allowed us to gain new insights into the culture and chronology of the European Copper Age.
    • The Kennewick Skeleton: Chronological and Biomolecular Contexts

      Taylor, R. E.; Smith, David Glenn; Southon, John R. (Department of Geosciences, The University of Arizona, 2001-01-01)
      A human skeleton recovered near Kennewick, Washington, USA in 1996 has been dated to the early Holocene on the basis of multiple radiocarbon determinations, an analysis of a style of a temporally diagnostic projectile point found embedded in the ilium of the skeleton, and geological investigations of the locality where the skeleton was recovered. Based on morphological criteria, the Kennewick skeleton, which is one of the most complete early Holocene human skeletons recovered so far in the Western Hemisphere, appears to be more similar to those of modern South Asians and Europeans than to modern Native Americans or to contemporary indigenous populations of Northeast Asia.
    • The Late Quaternary Sedimentary Record of Reykjanes Ridge, North Atlantic

      Prins, M. A.; Troelstra, S. R.; Kruk, R. W.; van der Borg, K.; de Jong, A. F. M.; Weltje, G. J. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Variability in surface and deep ocean circulation in the North Atlantic is inferred from grain-size characteristics and the composition of terrigenous sediments from a deep-sea core taken on Reykjanes Ridge, south of Iceland. End-member modeling of grain size data shows that deep-ocean circulation in this area decreased significantly during periods of maximum iceberg discharge. The episodes of reduced circulation correlate with the cold and abrupt warming phases of the Dansgaard-Oeschger cycles as recognized in the Greenland ice cores.
    • The Site of Verrebroek 'Dok' and its Contribution to the Absolute Dating of the Mesolithic in the Low Countries

      Van Strydonck, Mark J. Y.; Crombé, Philippe; Maes, Ann (Department of Geosciences, The University of Arizona, 2001-01-01)
      The wetland site of Verrebroek “Dok” situated in northern Belgium is one of the largest and best dated locations of Mesolithic material in northwestern Europe. Salvage excavations organized since 1992 at this large, unstratified open-air settlement have revealed more than 50 spatially independent artifact concentrations with traces of numerous fireplaces. Single entity dating of charred hazelnut shells from surface-hearths and charcoal from hearth-pits was used to obtain information not only on the sites duration, but also on the relation between the surface hearths and the hearth-pits. The dates were also used to look at discrepancies between the radiocarbon chronology and the typo-chronology of the lithic artifacts.
    • The Source of the Yarkon Springs, Israel

      Avisar, D.; Kronfeld, J.; Kolton, J.; Rosenthal, E.; Weinberger, G. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Radiocarbon and tritium analyses are used to show that the accepted conceptual hydrological model of the Yarkon-Taninim aquifer is untenable. The conventional model would have the groundwater flow in the carbonate Judea Group aquifer from the Beer Sheva region in the south to discharge at the Yarkon springs. Moreover, the conventional model considers the Judea Group aquifer to be a single hydrological entity. However, analysis of the Yarkon springs and surrounding wells demonstrate that it is stratified into upper and lower aquifers. The water in the deeper aquifer is fresher, cooler and younger compared to the water in the overlying aquifer. The deeper aquifer water type is identical in composition to the Ca-Mg-HCO3 Judean Hills recharge water immediately to the east. It is this recharge water that is dominant at the Yarkon Springs. There appears to be no derived appreciable contribution of groundwater from the Beersheva region in the south. Thus the currently accepted hydrologic model is in need of serious revision. The present study introduces new and high quality groundwater resources to be target for exploitation.
    • The Varying Radiocarbon Activity of Some Recent Submerged Estonian Plants Grown in the Early 1990s

      Olsson, Ingrid U.; Kaup, Enn (Department of Geosciences, The University of Arizona, 2001-01-01)
      Eleven samples of aquatic plants from three Estonian lakes were analyzed for their radiocarbon content in a collaboration between the laboratories in Tallinn and Uppsala. delta-13C values for the actual species were compiled to allow normalization of activities measured in Tallinn without delta-13C values. The range for well determined species is usually a few per mil and the statistical uncertainty greater than or equal to 1 per mil delta-13C values vary considerably for different Potamogeton species and Myriophyllum spp. Lake Antu Sinijarv and Lake Päidre are hard-water lakes containing 300 and 200 mg HCO3-/L, respectively. One sample consisted of a carbonate crust deposited on a Ceratophyllum demersum plant in L. Antu Sinijarv. Its Delta-14C value was -147.3 +/6.7 per mil in 1990, whereas the plant had a value of -74.1 +/8.0 per mil (delta-13C = -35.0 per mil). The same species in L. Päidre had a Delta-14C value of +8.0 +/8.8 per mil (delta-13C = -25.2 per mil) in 1992. Other species in L. Päidre contained more 14C, from a Delta-14C value of about +30 per mil to about +155 per mil, the latter value measured in Tallinn on floating leaves of Nuphar lutea, close to that of the contemporaneous atmospheric CO2. In the third lake, Lake Punso, containing >30 mg HCO3-/L, the stems of Nuphar lutea exhibited in 1990 a memory effect: the activity, Delta-14C = 209.6 +/10.3 per mil, significantly exceeded that of the contemporaneous atmospheric CO2. However, the floating leaves of the same plant had the Delta-14C value 143.1 +/10.0 per mil, close to the atmospheric 14C level in 1990. The memory is explained by nutrients stored in the root stock, used when the growth starts.
    • Towards a Radiocarbon Chronology of the Late-Glacial: Sample Selection Strategies

      Walker, M. J. C.; Bryant, C.; Coope, G. R.; Harkness, D. D.; Lowe, J. J.; Scott, E. M. (Department of Geosciences, The University of Arizona, 2001-01-01)
      This paper outlines a dating program designed to test the reproducibility of radiocarbon dates on different materials of Late-Glacial age (plant macrofossils, fossil beetle remains, and the "humic" and "humin" chemical fractions of limnic sediments) using a combination of radiometric (beta counting) and accelerator mass spectrometry (AMS) techniques. The results have implications for the design of sampling strategies and for the development of improved dating protocols, both of which are important if a high-precision 14C chronology for the Late-Glacial is to be achieved.
    • Transport of Sellafield-Derived 14C from the Irish Sea Through the North Channel

      Gulliver, Pauline; Cook, Gordon T.; MacKenzie, Angus B.; Naysmith, Philip; Anderson, Robe (Department of Geosciences, The University of Arizona, 2001-01-01)
      Since the early 1950s, the Sellafield nuclear fuel reprocessing plant in Northwest England has released radiocarbon into the Irish Sea in a mainly inorganic form as part of its authorized liquid effluent discharge. In contrast to the trend in which the activities of most radionuclides in the Sellafield liquid effluent have decreased substantially, 14C discharges have increased since 1994–95. This has largely been due to a policy change favoring marine discharges over atmospheric discharges. 14C is radiologically important due to its long half life, mobility in the environment, and propensity for entering the food chain. Current models for radionuclide dispersal in the Irish Sea are based on a reversible equilibrium distribution coefficient (kd), an approach which has been shown to be inadequate for 14C. Development of predictive models for the fate of Sellafield-derived 14C requires a thorough understanding of the biogeochemical fluxes between different carbon reservoirs and the processes controlling the net flux of 14C out of the Irish Sea, through the North Channel. In this study, both an empirical and a halving time approach indicate that close to 100% of the 14C that is discharged from Sellafield is dispersed beyond the Irish Sea on a time-scale of months in the form of DIC, with little transfer to the PIC, POC, and DOC fractions, indicating that the “dilute and disperse” mechanism is operating satisfactorily. This is consistent with previous research that indicated little transfer of 14C to Irish Sea sediments. While significant 14C enhancements have been observed in the biota of the Irish Sea, this observation is not necessarily in conflict with either of the above as the total biomass has to be taken into account in any calculations of 14C retention within the Irish Sea.