• 14C AMS Dating the Transition from the Paleolithic to the Neolithic in South China

      Yuan, Sixun; Zhou, Guoxing; Guo, Zhiyu; Zhang, Zimo; Gao, Shijun; Li, Kun; Wang, Jiangjun; Liu, Kexing; Li, Bin; Lu, Xiangyang (Department of Geosciences, The University of Arizona, 1995-01-01)
      To study the transition from the Paleolithic to the Neolithic period and its duration, samples of charcoal, bone, flowstone and shells excavated from Bailiandong and Miaoyan caves, Guangxi Zhuang autonomous region, South China were dated using the Peking University AMS facility and liquid scintillation counter. The remains excavated from these sites show typical characteristics of the transition from the Paleolithic to the Neolithic. Radiocarbon dating results show a rapid transition from ca. 20 to 10 ka BP.
    • 14C Calibration in the Southern Hemisphere and the Date of the Last Taupo Eruption: Evidence from Tree-Ring Sequences

      Sparks, R. J.; Melhuish, W. H.; McKee, J. W. A.; Ogden, John; Palmer, J. G.; Molloy, B. J. (Department of Geosciences, The University of Arizona, 1995-01-01)
      Tree rings from a section of Prumnopitys taxifolia (matai) covering the period AD 1335-1745 have been radiocarbon dated and used to generate a 14C calibration curve for southern hemisphere wood. Comparison of this curve with calibration data for northern hemisphere wood does not show a systematic difference between 14C ages measured in the northern and southern hemispheres. A floating chronology covering 270 yr and terminating at the last Taupo (New Zealand) eruption, derived from a sequence of 10-yr samples of tree rings from Phyllocladus trichomanoides (celery pine, or tanekaha), is also consistent with the absence of a systematic north-south difference, and together with the matai data, fixes the date of the Taupo eruption at AD 232 +/15.
    • 14C Dating of an Israelite Biblical Site at Kuntillet Ajrud (Horvat Teman)

      Meshel, Zeev; Carmi, Israel; Segal, Dror (Department of Geosciences, The University of Arizona, 1995-01-01)
      The Israelite site of Kuntillet Ajrud in northern Sinai contains unique drawings and inscriptions in ancient Hebrew and Phoenician. It is a single-phase site dated archaeologically to ca. 800 BCE. We considered this site a good test case for comparing archaeological with 14C datings. The dates are in agreement, confirming that 14C dating is useful in dating Iron-Age II sites.
    • 14CH4 Emissions from Nuclear Power Plants in Northwestern Europe

      Eisma, Roos; Vermeulen, Alex T.; van der Borg, Klaas (Department of Geosciences, The University of Arizona, 1995-01-01)
      We measured the 14C content of atmospheric methane at a 200-m-high sampling station in the Netherlands. Combined with trajectories and a transport model, it is possible to estimate the 14CH4 emissions from nuclear power plants in northwestern Europe. We demonstrate here two different methods of analyzing the data: forward modeling and an inverse method. Our data suggest that the emissions from pressurized water reactors are 260 +/50 GBq per GW installed power per year, ca. 1.6 +/0.4 times higher than generally assumed. We also find that, in addition to the known nuclear sources of 14CH4 (pressurized and boiling water reactors), there are two very strong sources of 14CH4 (520 +/200 and 1850 +/450 GBq yr-1, respectively), probably two test reactors near the sampling station.
    • 1996 Price List

      Department of Geosciences, The University of Arizona, 1995-01-01
    • 7th International Conference on Accelerator Mass Spectrometry

      Department of Geosciences, The University of Arizona, 1995-01-01
    • A 30,000-Year Pollen and Radiocarbon Record from Highland Sumatra as Evidence for Climatic Change

      Maloney, B. K.; McCormac, F. G. (Department of Geosciences, The University of Arizona, 1995-01-01)
      We examine the pollen analytical and 14C sequences from two Sumatra highland sites, Pea Bullok (2 degrees 15'N, 99 degrees 02'E) and Danau di-Atas (1 degree 04'S, 100 degrees 46'E). The pollen diagrams do not correlate particularly well, possibly because two of the samples from Danau di-Atas analyzed by radioactive decay counting earlier should be infinite. Other complications are differences in the type of site, local topography, pollen sums used and difficulty in distinguishing between pollen taxa from local and regional vegetation. The older material from Pea Bullok was AMS dated.
    • A Bayesian Approach to the Use of 14C Dates in the Estimation of the Age of Peat

      Christen, J. A.; Clymo, R. S.; Litton, C. D. (Department of Geosciences, The University of Arizona, 1995-01-01)
      Peatlands occupy a significant portion of the land surface of the Earth and form a large carbon store. Most peat-forming systems have two layers. The upper layer, the acrotelm, fixes carbon by photosynthesis, loses some of it by decay and passes the remainder on to the lower layer, the catotelm. In the catotelm, decay continues at a slower rate. Mathematical models of the growth of the catotelm have been proposed which relate the cumulative mass of peat above a particular depth to calendar age of the peat at that depth. We demonstrate how 14C dating and the Bayesian approach to data analysis can be used to make inferences about the relation between calendar age and cumulative mass, and to estimate the accumulation and decay rates.
    • A Beta-Counting System Linked to a Personal Computer

      Omoto, Kunio (Department of Geosciences, The University of Arizona, 1995-01-01)
      The automatic beta-counting system plays a significant role in obtaining high-level reproducibility and reliability in conventional radiocarbon dating. I review here the results achieved by using the "Fully Automatic Radiocarbon Dating System" developed by Omoto (1982). Since setting up the system in 1981, I was able not only to save operator time in beta counting, but also to obtain accurate dates with only minimal uncertainties. Another positive result was the introduction of the automatic voltage correction program, which produced excellent results for counting sample materials over a long period.
    • A Chronological Guide to International Radiocarbon Conferences and Publications

      Department of Geosciences, The University of Arizona, 1995-01-01
      A Chronological Guide to International Radiocarbon Conferences and Publications
    • A Comparative Study of Monsoonal and Non-Monsoonal Himalayan Lakes, India

      Kusumgar, Sheela; Agrawal, D. P.; Deshpande, R. D.; Ramesh, Rengaswamy; Sharma, C.; Yadava, M. G. (Department of Geosciences, The University of Arizona, 1995-01-01)
      Sedimentological, mineral magnetic and carbon isotopic studies on cores from Mansar Lake in the Jammu area provide paleomonsoonal history dating back to 580 BC. From ca. 580 BC to AD 300, the region experienced precipitation similar to the present, whereas from AD 300 to 1400, the monsoon was relatively subdued. A small excursion ca. AD 1100 suggests an effect of medieval warming. Studies in the Kumaon region did not provide a proper precipitation record, as anthropogenic activity interfered with sedimentation. Manasbal Lake in Kashmir gave an inversion of 14C chronology due to younger paleosols in the drainage basin. Further, the episodic nature of sedimentation in Manasbal Lake hampered the reconstruction of precipitation history in the area.
    • A Comparison of Marine and Terrestrial Radiocarbon Ages from Northern Chile

      Southon, John R.; Oakland Rodman, Amy; True, Delbert (Department of Geosciences, The University of Arizona, 1995-01-01)
      The calibration of radiocarbon dates on marine materials involves a global marine calibration with regional corrections. Data from well-associated marine and terrestrial materials in archaeological artifacts from northern Chile indicated that the calibration is valid for the period AD 200-900 and suggest that coastal upwelling intensities during that period were similar to those of the early 20th century.
    • A Computer-Based Database for Radiocarbon Dates of Central Andean Archaeology

      Michczyński, Adam; Krzanowski, Andrzej; Pazdur, Mieczysław F.; Ziołkowski, Mariusz S. (Department of Geosciences, The University of Arizona, 1995-01-01)
      We established a database of 14C dates from archaeological sites of the Central Andes region of Peru, Ecuador and Bolivia on an IBM PC-compatible microcomputer running on an MS-DOS operating system using software package dBASE IV, version 1.1. Relevant data are stored in three DBF-type database files. The file ANDY.DBF contains information on dates and samples; REFERENC.DBF contains references to relevant publications and CALAND.DBF contains calibrated dates. The total number of records of the ANDY database slightly exceeds 2650.
    • A Correction for In-Situ 14C in Antarctic Ice with 14CO

      van Roijen, Job; van der Borg, Klaas; de Jong, Arie; Oerlemans, Johannes (Department of Geosciences, The University of Arizona, 1995-01-01)
      We use a dry extraction method to obtain trapped CO2 of shallow ice cores from a blue ice area of East Antarctica. In-situ-produced 14C extracted in 14CO2 and 14CO concentrations show a mean ratio of 3.4 +/0.4. Correction for insitu 14CO2 resulted in ice ages within 7-13 ka. The accumulation and ablation rates determined from the in-situ production of 7-20 cm yr-1 and 10-13 cm yr-1, respectively, agree with field measurements, and thus indicate close to total efficiency of extraction.
    • A Data Acquisition System for Proportional Counters at Gliwice

      Michczyński, Adam; Goslar, Tomasz; Pazdur, Anna; Pazdur, Mieczysfaw F. (Department of Geosciences, The University of Arizona, 1995-01-01)
      We present here the principal ideas of a new, fully computerized data acquisition system with pulse-rise background reduction, developed in the Gliwice Radiocarbon Laboratory, and our first results. The new system uses a microprocessor-controlled pulse and coincidence analyzer for acquisition of data from 3 of 4 proportional counter sets. The analyzer acquires and stores information on the pulse's amplitudes and rise-times and their coincidence with guard counters and radiofrequency shield. This feature allows us to separate pulses using anticoincidence information and pulse-shape discrimination. The described method of background reduction led to a significant increase in the factor of merit on 2 of 3 counters tested.
    • A General Computer Program for Radiocarbon Dating Laboratories

      González-Gómez, Cecilio (Department of Geosciences, The University of Arizona, 1995-01-01)
      Radiocarbon dating laboratories deal with many types of data and calculations, which include information on received and dated samples, age calculations and storage of results, printed reports to submitters and graphs plotted from sample measurements. I describe a computer program, designed to run on any PC-compatible computer with a hard disk, that can handle all the functions of a conventional liquid scintillation counting radiocarbon dating laboratory.
    • A Method for Quantifying Deep-Sea Carbonate Dissolution Using 14C Dating

      van Kreveld, S. A.; Ganssen, G. M.; van der Plicht, J. E.; Melkert, M. M.; Troelstra, S. R.; van der Borg, K.; de Jong, Arie (Department of Geosciences, The University of Arizona, 1995-01-01)
      We quantified the rate of carbonate dissolution with increasing water depth by taking the difference in the carbonate mass accumulation rate of deep (3393-4375 m) core top sediments from the shallowest one (3208 m), which we assumed was unaffected by dissolution. This method depends on high quality 14C dates that we calibrated to calendar years for calculating sedimentation rates. Our results show low (ranging from 0 to 0.3 g cm-2 ka-1) and high (ranging from 1.5 to 1.7 g cm-2 ka-1) carbonate dissolution rates, above and below 4000 m, respectively. Therefore, we interpret the sudden increase in the carbonate dissolution rate at 4000-m water depth to mark the lysocline.
    • A Note Concerning "Location-Dependent Differences in the 14C Content of Wood" by McCormac et al

      Damon, Paul E. (Department of Geosciences, The University of Arizona, 1995-01-01)
    • A Single-Year delta-13C Chronology from Pinus tabulaeformis (Chinese Pine) Tree Rings at Huangling, China

      Leavitt, Steven W.; Yu, Liu; Hughes, Malcolm K.; Rongmo, Liu; Zhisheng, An; Gutierrez, Graciela M.; Danzer, Shelley R.; Xuemei, Shao (Department of Geosciences, The University of Arizona, 1995-01-01)
      Individual rings from 1899-1990 were pooled from four radii of four cross-sections obtained from trees at a forest site near Huangling, north of Xian in north central China. Splits of wood ground to 20-mesh were analyzed independently at both the Xian and Arizona laboratories, using their respective methods for cellulose isolation, combustion and mass-spectrometric analysis. The delta-13C results were highly correlated (r2 = 0.66) and absolute values typically within 0.2-0.3ppm. Inter-tree variability was estimated as 1-1.5 ppm. The Huangling delta-13C curve shows an overall downward trend with year-to-year fluctuations of up to 1.5 ppm superimposed. A subset of delta-13C maxima corresponded with below-normal precipitation and above-normal temperature in May and June, and minima were associated with above-normal precipitation and below-normal temperature in May and June, perhaps signaling early arrival of the East Asian Summer Monsoon. The generally poor climate correlations with all delta-13C values, however, could be a consequence of the fairly mesic environment or of human disturbance. Chronologies of isotopic discrimination (Delta) and Ci/Ca had flat slopes, suggesting the delta-13C trend was driven by global rather than local effects.
    • A Survey of Environmental 14C Levels in Hong Kong

      Leung, P. L.; Stokes, M. J.; Qiu, S. H.; Cai, L. Z. (Department of Geosciences, The University of Arizona, 1995-01-01)
      As an industrialized city, Hong Kong annually consumes a large amount of fossil fuel. In addition, the Daya Bay Nuclear Power Plant in Shenzhen, Guangdong Province, has just begun operation 20 km from Hong Kong. These factors suggest that it may be appropriate and significant to examine the variation of atmospheric 14C levels in Hong Kong. We have collected and tested a variety of samples from different parts of Hong Kong; terrestrial annual grasses, marine plants and atmospheric CO2. We measured their 14C activity and compared it with that of cassia oil samples from Guangxi Province, China. The values obtained indicate that environmental 14C levels in the Hong Kong region agree with those found in Guangxi, both of which are significantly higher than the levels predicted by Povinec, Chudy and Sivo (1986).