• INGEIS Radiocarbon Laboratory Dates IV

      Cordero, Roberto; Lanzelotti, Sonia; Panarello, Héctor (Department of Geosciences, The University of Arizona, 2002-01-01)
    • Marine Reservoir Corrections for the Indian Ocean and Southeast Asia

      Southon, John; Kashgarian, Michaele; Fontugne, Michel; Metivier, Bernard; Yim, Wyss W-S. (Department of Geosciences, The University of Arizona, 2002-01-01)
      We have measured radiocarbon in prebomb known-age shells and coral from the Indian Ocean and southeast Asia to determine marine reservoir age corrections. Western Indian Ocean results show a strong 14C depletion due to upwelling in the Arabian Sea, and indicate that this signal is advected over a wide area to the east and south. In contrast, the surface waters of the South China Sea contain relatively high levels of 14C, due in part to the input of well-equilibrated water masses from the western Pacific. The easternmost regions of the Indian Ocean are also strongly influenced by the flowthrough of Pacific waters north of Australia.
    • Novel Statistical Model for a Piece-Wise Linear Radiocarbon Calibration Curve

      Gómez Portugal Aguilar, Delil; Litton, Cliff D.; O'Hagan, Anthony (Department of Geosciences, The University of Arizona, 2002-01-01)
      The process of calibrating radiocarbon determinations onto the calendar scale requires the setting of a specific statistical model for the calibration curve. This model specification will bear fundamental importance for the resulting inference regarding the parameter of interest—namely, in general, the calendar age associated to the sample that has been 14C-dated. Traditionally, the 14C calibration curve has been modelled simply as the piece-wise linear curve joining the (internationally agreed) high-precision calibration data points; or, less frequently, by proposing spline functions in order to obtain a smoother curve. We present a model for the 14C calibration curve which, based on specific characteristics of the dating method, yields a piece-wise linear curve, but one which rather than interpolating the data points, smooths them. We show that with this specific model if a piece-wise linear curve is desired, an underlying random walk model is implied as covariance structure (and vice versa). Furthermore, by making use of all the information provided by the calibration data in a comprehensive way, we achieve an improvement over current models by getting more realistic variance values for the calibration curve.
    • A Radiocarbon Age Calculation Program for Windows

      Gallagher, D.; McGee, E. J.; Mitchell, P. I. (Department of Geosciences, The University of Arizona, 2002-01-01)
      The management of counting files, the calculation of radiocarbon age, and the creation and maintenance of databases for storage and retrieval of laboratory data are time-consuming and exacting tasks. These routine functions are essential to the successful operation of all 14C dating laboratories. However, since the number of 14C dating laboratories worldwide is rather limited, it is unlikely that a commercial software company will produce a program for use in 14C age calculation and associated data management. We have therefore developed Windows based software to meet some of these needs. The program described here offers a user-friendly interface to assist with: Execution of age and error calculations; Reducing the possibility of human error during the lengthy age calculation procedure; Developing a single entry system that simultaneously runs dating algorithms and compiles a database of all samples processed by a laboratory. We now make the program and the program code available to the 14C dating community. We hope that this program will be a useful tool in routine laboratory operation and can be further developed in the future.
    • Radiocarbon, Volume 44, Number 1 (2002)

      Department of Geosciences, The University of Arizona, 2002-01-01
    • Late Quaternary Chronology and Stratigraphy of Twelve Sites on Kaua'i

      Burney, David A. (Department of Geosciences, The University of Arizona, 2002-01-01)
      Twelve new sites on Kaua'i provide an island-wide view of late Quaternary (near time) environments on the oldest of the major Hawaiian Islands. Radiocarbon-dated lithologies are compared for estuarine sites on windward and leeward coasts, interior peat bogs ranging from 169 to 1220 m in elevation, prehistoric fishponds, and a sinkhole paleolake in the Maha'ulepu cave system. Terrestrial sedimentation begins in many coastal sites about 6000 cal BP, as sea level approached modern levels. Prehuman sedimentation rates were quite low in all these sites, generally <2 mm/yr, although coastal sites in the late Holocene were subject to major episodic sediment influx from extreme events, including tsunamis, hurricanes, and floods. Interior sites are generally older, having accumulated humic clay and peat layers at least since the late Pleistocene. Since the arrival of humans less than two millennia ago, sedimentation rates have increased in some coastal sites, and further local increases (as much as two orders of magnitude) have occurred since European arrival. Evidence from sites containing fossils of extinct terrestrial snails is consistent with the hypothesis that human-caused extinctions have proceeded in three phases, corresponding to losses (generally the largest species) occurring soon after the arrival of the first humans, followed by a second wave of extinction in late prehistoric times, and a third after European colonization. Dating of sediments from fishponds constructed or enhanced by prehistoric Polynesians suggests that this early form of aquaculture was initiated on Kaua'i by about 830 +/50 BP. The most elaborate example of fishpond construction in the Hawaiian Islands, the Alekoko or Menehune fishpond on Kaua) i's southeast coast, was probably undertaken by 580 +/30 BP.
    • Coastal Response to Changes in Sea Level since the Last 4500 BP on the East Coast of Tamil Nadu, India

      Achyuthan, Hema; Baker, V. R. (Department of Geosciences, The University of Arizona, 2002-01-01)
      Geomorphology, clay mineral composition, and radiocarbon dates from Muttukadu to Marakkanam estuaries and the tidal zone along the east coast of Tamil Nadu, India, have been used to reconstruct coastal evolution between approximately 4500 and 1100 BP. Formation of alternate oyster beds with intervening tidal clay units indicate fluctuation in the sea level may be a consequence of changes in the Mid-Holocene sedimentation pattern and coastal configuration. 14C dates from Muttukadu indicate a rapid relative sea-level rise (RSL) subsequent to 3500 BP and tidal flat sedimentation between 3475 and 3145 BP. Marine conditions along the east coast area returned around 1900 BP. Comparison of dates with other sites, e.g. Muttukadu, Mammallapuram, and Marakkanam, points toward short removal of marine conditions, ample sediment supplies in the tidal zones, and neotectonic activity. Reactivation of the north-south trending fault line occurred not earlier than approximately 1050 BP. Our study indicates that Middle to Late Holocene coastal sedimentation and the chronology of the tidal zone formation have been strongly influenced by local factors. These have provided considerable scope for internal reorganization with changing coastal processes.
    • Radiocarbon Dating of Buried Holocene Soils in Siberia

      Orlova, Lyubov A.; Zykina, Valentina S. (Department of Geosciences, The University of Arizona, 2002-01-01)
      We have constructed a detailed chronological description of soil formation and its environments with data obtained on radiocarbon ages, palynology, and pedology of the Holocene buried soils in the forest steppe of western and central Siberia. We studied a number of Holocene sections, which were located in different geomorphic situations. Radiocarbon dating of materials from several soil horizons, including soil organic matter (SOM), wood, peat, charcoal, and carbonates, revealed three climatic periods and five stages of soil formation in the second part of the Holocene. 14C ages of approximately 6355 BP, 6020 BP, and 5930 BP showed that the longest and most active stage is associated with the Holocene Climatic Optimum, when dark-grey soils were formed in the forest environment. The conditions of birch forest steppe favored formation of chernozem and associated meadow-chernozem and meadow soils. Subboreal time includes two stages of soil formation corresponding to lake regressions, which were less intense than those of the Holocene Optimum. The soils of that time are chernozem, grassland-chernozem, and saline types, interbedded with thin peat layers 14C dated to around 4555 BP, 4240 BP and 3480 BP, and 3170 BP. Subatlantic time includes two poorly developed hydromorphic paleosols formed within inshore parts of lakes and chernozem-type automorphic paleosol. The older horizon was formed during approximately 2500-1770 BP, and the younger one during approximately 1640-400 BP. The buried soils of the Subatlantic time period also attest to short episodes of lake regression. The climate changes show an evident trend: in the second part of the Atlantic time period it was warmer and drier than at present, and in the Subboreal and Subatlantic time periods the climate was cool and humid.
    • AMS-14C Chronology of a Lacustrine Sequence from Lake Langano (Main Ethiopian Rift): Correction and Validation Steps in Relation with Volcanism, Lake Water and Carbon Balances

      Gibert, Elisabeth; Travi, Yves; Massault, Marc; Tiercelin, Jean-Jacques; Chernet, Tesfaye (Department of Geosciences, The University of Arizona, 2002-01-01)
      Located in the Ziway-Shala Basin of the Main Ethiopian Rift, Lake Langano is part of an asymmetric half-graben, defined by a series of north-northeast-trending faults in the tectonically active zone of the rift. A 15-m deep succession of organic homogeneous muds, silts, bioclastic sands, and pyroclastic layers was cored in 1994. The definition of a certified radiocarbon chronology on these deposits required the indispensable establishment of modern hydrological and geochemical balances. The isotopic contents of the total dissolved inorganic carbon (TDIC) of surface water clearly show the influence of a deep CO2 rising along the main fault crossing the lake basin. The 5.8 pMC disequilibrium existing in 1994 with the atmosphere likely produces the aging of authigenic materials developing at the lake surface. However, with a mean residence time of approximately 15 years, this apparent 14C aging of Lake Langano water still integrates the 14C produced by the nuclear tests in the 1960s. Reconstructing the natural 14C activity of the lake TDIC allows for the quantification of the deep CO2 influence, and for the correction of AMS-14C datings performed along the core. The correction of the AMS14C chronology defined on Lake Langano allows for a better understanding of paleohydrological changes at a regional scale for at least the last 12,700 cal BP.
    • The Use of Raman Spectroscopy to Monitor the Removal of Humic Substances from Charcoal: Quality Control for 14C Dating of Charcoal

      Alon, Dani; Mintz, Genia; Cohen, Illit; Weiner, Steve; Boaretto, Elisabetta (Department of Geosciences, The University of Arizona, 2002-01-01)
      One of the largest sources of uncertainty in radiocarbon dating stems from the sample pretreatment procedures used to minimize contamination. A major source of carbon contamination in charcoal from archaeological sites is humic substances carried by groundwater. Here we present a method, independent of 14C dating itself, to evaluate the effectiveness of the cleaning procedure of charcoal. Raman spectra of mixtures of humic substances (HS) and laboratory prepared charcoal indicate that Raman spectroscopy can be used as a semi-quantitative measure of the amount of humic substances associated with archaeological charcoal. Raman spectral analysis of archaeological charcoal samples subjected to different cleaning regimes supports this contention. Such measurements can provide quality control for charcoal preparation procedures and may assist in the interpretation of carbon-dating results.
    • Challenges in Radiocarbon Dating Organic Carbon in Opal-Rich Marine Sediments

      Zheng, Yan; Anderson, Robert F.; Froelich, Philip N.; Beck, Warren; McNichol, Ann P.; Guilderson, Thomas (Department of Geosciences, The University of Arizona, 2002-01-01)
      We explored the reliability of radiocarbon ages obtained on organic carbon phases in opal-rich Southern Ocean sediments. Paired biogenic carbonate and total organic carbon (TOC) 14C analyses for three Southern Ocean cores showed that the TOC ages were systematically younger than the carbonate ages. Carbonate ages were consistent with oxygen isotopic and bio-stratigraphy, indicating error in TOC ages that could be explained by 5-24% of modern carbon contamination of TOC samples. Two possible sources of contamination are: 1) adsorption of atmospheric CO2 or volatile organic compounds to reactive opal surface sites, and 2) fixation of atmospheric CO2 by chemosynthetic bacteria during core storage. In an effort to reduce the modern carbon contamination, diatoms were separated from sediments, purified, and pre-oxidized by concentrated nitric and perchloric acids to permit dating of opal-intrinsic organic carbon (approximately 0.1-0.3% by weight). 14C ages of chemically pre-oxidized opal showed a significant amount of modern carbon contamination, from 11 to 32%, indicating adsorption from the atmosphere of modern carbon onto opal surfaces that were previously cleaned by acid oxidation. Several experiments designed to eliminate the modern C contamination were attempted, but so far we have not been able to obtain a radiocarbon age on 14C-dead Southern Ocean opal-rich sediments, either bulk TOC or purified diatom opal samples, as old as our procedural blank.
    • Carbon Dynamics in Vertisols as Revealed by High-Resolution Sampling

      Becker, Heidmann Peter; Andresen, Olaf; Kalmar, Dov; Scharpenseel, Hans Wilhelm; Yaalon, Dan H. (Department of Geosciences, The University of Arizona, 2002-01-01)
      Two Vertisol soil profiles under xeric soil moisture regimes, located at Qedma and Akko, Israel, were investigated and compared to a profile under ustic moisture regime, located in Hyderabad, India. Samples were taken in complete successive 2 cm thin layers down to about 180 cm depth or more. Organic and inorganic carbon were analyzed with regard to 13C and 14C concentrations. While all soils have radiocarbon ages of several thousand years BP, the depth distributions reveal substantial differences between the soil carbon dynamics. 14C and, less pronounced, delta-13C clearly reflect the pedoturbation process. Further, its strength is found to be related to mainly soil moisture regime, then clay content and land use. In one soil, a change of growing from C4 to C3 crops in the past can be concluded from the delta-13C depth distribution.
    • Why Early-Historical Radiocarbon Dates Downwind from the Mediterranean are Too Early

      Keenan, Douglas J. (Department of Geosciences, The University of Arizona, 2002-01-01)
      Several authors have claimed that radiocarbon dates in the Ancient Near East are too early. Herein, a hypothesis that might explain this is presented. Marine degassing of "old" carbon (i.e. 14C-deficient C), induced by upwelling of old subsurface water, has been observed, n modern times, to cause century-scale 14C ages in the surface atmosphere. A review of the Mediterranean Sea post-ice-age circulation concludes that the subsurface waters became very old, primarily due to millennia-long stagnation. It is hypothesized that as the stagnation ended, subsurface waters were brought towards the surface, where they degassed old carbon. Additionally, Anatolian dendrochronology is shown to not contradict the hypothesis.
    • From the Editor

      Jull, A. J. Timothy (Department of Geosciences, The University of Arizona, 2002-01-01)
    • AMS Dating of Human Bone from Palau: New Evidence for a Pre-2000 BP Settlement

      Fitzpatrick, Scott M. (Department of Geosciences, The University of Arizona, 2002-01-01)
      Direct dating of a human bone fragment from the Chelechol ra Orrak site (western Micronesia) has yielded one of the earliest dates for Palau thus far. This date compares well with recently collected paleoenvironmental evidence and radiocarbon dates on Babeldaob Island suggesting that settlement of the Palauan archipelago took place much earlier than previously thought.
    • Determination of the Radiocarbon Age of Parchment of the Vinland Map

      Donahue, D. J.; Olin, J. S.; Harbottle, G. (Department of Geosciences, The University of Arizona, 2002-01-01)
      The Vinland Map, drawn on a 27.8 x 41.0 cm parchment bifolium, is housed in the Beinecke Rare Book and Manuscript Library at Yale University. In the northwest Atlantic Ocean, it shows "the Island of Vinland, discovered by Bjarni and Leif in company." Skelton, Marston, and Painter (Skelton et al. 1965, 1995) firmly argued the map's authenticity, associating it with the Council of Basle (AD 1431-1449), that is, half a century before Columbus's voyage. Nevertheless, vigorous scholarly questioning of the map's authenticity has persisted (Washburn 1966; McCrone 1974; Olin and Towe 1976; Cahill et al. 1987; McCrone 1988; Towe 1990). We have determined the precise radiocarbon age of the map's parchment by accelerator mass spectrometry (AMS). The one-sigma calibrated calendrical date range is AD 1434 +/11 years: the 95% confidence level age range is AD 1411-1468.
    • Differences in 14C Age Between Stratigraphically Associated Charcoal and Marine Shell from the Archaic Period Site of Kilometer 4, Southern Peru: Old Wood or Old Water?

      Kennett, Douglas J.; Ingram, B. Lynn; Southon, John R.; Wise, Karen (Department of Geosciences, The University of Arizona, 2002-01-01)
      Consistently large differences occur in the calibrated 14C ages of stratigraphically associated shell and charcoal samples from Kilometer 4, an Archaic Period archaeological site located on the extreme south coast of Peru. A series of nine shell and charcoal samples were collected from a Late Archaic Period (approximately 6000-4000 BP) sector of the site. After calibration, the intercepts of the charcoal dates were approximately 100-750 years older than the paired shell samples. Due to the hyper-arid conditions in this region that promote long-term preservation of organic material, we argue that the older charcoal dates are best explained by people using old wood for fuel during the Middle Holocene. Given this "old wood" problem, marine shell may actually be preferable to wood charcoal for dating archaeological sites in coastal desert environments as in southern Peru and Northern Chile.
    • Radiocarbon and Stable Isotope Analyses of Archaeological Bone Consolidated with Hide Glue

      Takahashi, C. M.; Nelson, D. E.; Southon, J. S. (Department of Geosciences, The University of Arizona, 2002-01-01)
      We tested a simple method for removing a collagen-based glue preservative from bone destined for radiocarbon and stable isotope analyses. The method is sufficient for bone samples from which only stable isotope measurements are required. For 14C dating, such samples of age less than about 10 ka can be adequately dated, but for older samples, the circumstances must be carefully evaluated.
    • Editorial Board

      Department of Geosciences, The University of Arizona, 2002-01-01
    • Reservoir Corrections for Marine Samples from the South Atlantic Coast, Santa Catarina State, Brazil

      Eastoe, C. J.; Fish, S.; Fish, P.; Gaspar, M. Dulce; Long, A. (Department of Geosciences, The University of Arizona, 2002-01-01)
      Coeval shell and charcoal from Santa Catarina State, Brazil, differ systematically in 14C content, indicating a reservoir effect in marine samples. For modern samples (AD 1939-2000) and archeological samples (2500-1595 BP), the mean 14C age difference between marine and atmospheric carbon is 220 +/20 years, the marine carbon being older. For three samples dated AD 1939-1944, a distinct reservoir correction of 510 +/10 years is also observed. The ages of archeological shell samples from Jabuticabeira may be corrected by subtracting 220 years from the apparent 14C ages.