• 32Si Dating of Marine Sediments from Bangladesh

      Morgenstern, Uwe; Geyh, M. A.; Kudrass, Herrmann Rudolf; Ditchburn, R. G.; Graham, I. J. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Appropriate dating tools are essential for paleoenvironmental studies. Cosmogenic 32Si with a half-life of about 140 years is ideally suited to cover the dating range 30-1000 years. Here we have applied scintillation spectrometry for detection of natural 32Si to date marine shelf sediments. High detection efficiency, combined with stable background, allows for the detection of extremely low 32Si specific activities found in such sediments with counting rates below one count per hour. For a sediment core from the Ganges-Brahmaputra delta 32Si dating yields mean sedimentation rates of 0.7 +/0.2 cm/yr for 50 to several hundred years BP and 3.1 +/0.8 cm/yr for the past 50 years. The four-fold increase of the sedimentation rate over the past 50 years may reflect increased sediment loads in the rivers due to increasing human colonization within the rivers' drainage basins.
    • Calibration of Lacustrine Sediment Ages Using the Relationship between 14C Levels in Lake Waters and in the Atmosphere: The Case of Lake Kinneret

      Stiller, Mariana; Kaufman, Aaron; Carmi, Israel; Mintz, Genia (Department of Geosciences, The University of Arizona, 2001-01-01)
      The source of endogenic organic and inorganic carbon in lacustrine sediments is the dissolved inorganic carbon (DIC) in the lake water. The relation between the radiocarbon levels of DIC in Lake Kinneret and of CO2 in the atmosphere has been investigated. The ratio of the former to the latter was found to be 0.814 +/0.013. This ratio is used for calibrating the age of the sediment according to the natural fluctuations in the atmospheric levels of 14C that occurred during the past 10,000 years.
    • Dating of Biodeposits of Oxalates at the Arc de Berà in Tarragona, Spain

      Girbal, J.; Prada, J. L.; Rocabayera, R.; Argemi, M. (Department of Geosciences, The University of Arizona, 2001-01-01)
      This research stems from an earlier study of the lichen covering with oxalate deposits at the Arc de Berà monument. The initial objective of dating these biodeposits opened up other questions concerning the structure of these deposits and how they were formed. Some dating results gave an absolute age greater than the monument itself, which posed various hypotheses on the possible ageing mechanisms.
    • Development of Accurate and Reliable 14C Chronologies for Loess Deposits: Application to the Loess Sequence of Nussloch (Rhine Valley, Germany)

      Hatté, Christine; Pessenda, Luiz Carlos; Lang, Andreas; Paterne, Martine (Department of Geosciences, The University of Arizona, 2001-01-01)
      Due to very high accumulation rates, loess sequences are best suited archives for the continental paleoclimate of glacial periods. Accurate chronologies cannot be easily established by radiocarbon-dating, because of the lack of organic macrorests, the only material for reliable 14C dating so far. A chemical protocol is reported to extract the organic matter of loess (organic carbon content lower than 0.1% by weight) for accelerator mass spectrometry (AMS) 14C dating. Sediments were taken from the loess sequence of Nussloch, for which a large dataset of luminescence ages (TL, IRSL/OSL) is available. The 14C chronology of the organic matter extracted from loess is in good agreement with the corresponding luminescence ages. It allows high resolution correlations with climatic proxy signals (magnetic susceptibility, malacological assemblages, delta-13C on organic matter, etc.) derived from the loess sequence and global environmental proxy records.
    • 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 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.
    • 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.