• Editorial Board

      Department of Geosciences, The University of Arizona, 2001-01-01
    • Environmental and Climatic Change as Recorded in Geological Sediments from the Arid to Semi-Arid Zone of China

      Zhou, Weijian; Zhengkun, Wu; Jull, A. J. T.; Burr, G.; Donahue, D. D.; Baosheng, Li; Head, J. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Stratigraphic investigations together with climatic proxy data measurements and reliable radiocarbon dating show a history of fluctuations of dry and wet environmental conditions in the arid to semi-arid zone of northern China since the late Pleistocene. Based on these data, we are able to reconstruct shifts of the desert margin in two period extremes, the last glacial maximum (21-15 ka) and the Holocene Optimum (9-5 ka). We have compared the present desert margin with that for the two extremes. The results indicate that a southward shift of the present margin of about 3 degrees in latitude might be caused by anthropogenic impact. Hence the influence of human activity must be taken into consideration for sustainable development and environment protection. Future research will be to find a two-way feedback existing between climate and anthropogenic impacts.
    • Further Attempts at Dating the Palynological Sequence of the Hula L07 Core, Upper Jordan Valley, Israel

      Weinstein, Evron M.; Vogel, J. C.; Kronfeld, J. (Department of Geosciences, The University of Arizona, 2001-01-01)
      The palynological sequence of the Hula L07 core was previously correlated with the global oxygen isotope stages 3-5, based on a radiocarbon age determination and comparison with other Levantine paleoclimatological curves. An attempt was made to validate this correlation with Th/U dating. Unlike typical European peat, which is acidic, the soil pH of the Hula peat is mildly basic. Not only does this contribute to the oxidation of palynomorphs, but it also helps to preserve the carbonate material that can be a variable mixture of allogenic, endogenic, and authigenic components. Each component may represent a different degree of uranium series disequilibrium. The thorium (232Th) concentrations of the carbonate are low. Total digestion or acid leach of the sample may not always enable the proper correction for initial thorium. The dating derived from a NaOH-extraction of the organic material, while giving apparently better ages, also suffers from the presence of the carbonate admixture. It appears that, while 14C dating can be considered suitable for the younger portions of the core, techniques based upon the U-series may not be as efficacious in dating this important record of climatic change.
    • High-Resolution AMS 14C Dating of Post-Bomb Peat Archives of Atmospheric Pollutants

      Goodsite, Michael E.; Rom, Werner; Heinemeier, Jan; Lange, Todd; Ooi, Suat; Appleby, Peter G.; Shotyk, William; van der Knapp, W. O.; Lohse, Christian; Hansen, Torben S. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Peat deposits in Greenland and Denmark were investigated to show that high-resolution dating of these archives of atmospheric deposition can be provided for the last 50 years by radiocarbon dating using the atmospheric bomb pulse. 14C was determined in macrofossils from sequential one cm slices using accelerator mass spectrometry (AMS). Values were calibrated with a general-purpose curve derived from annually averaged atmospheric 14CO2 values in the northernmost northern hemisphere (NNH, 30 degrees to 90 degrees N). We present a through review of 14C bomb-pulse data from the NNH including our own measurements made in tree rings and seeds from Arizona as well as other previously published data. We show that our general-purpose calibration curve is valid for the whole NNH producing accurate dates within 1-2 years. In consequence, 14C AMS can precisely date individual points in recent peat deposits within the range of the bomb-pulse (from the mid-1950s on). Comparing the 14C AMS results with the customary dating method for recent peat profiles by 210Pb, we show that the use of 137Cs to validate and correct 210Pb dates proves to be more problematic than previously supposed. As a unique example of our technique, we show how this chronometer can be applied to identify temporal changes in Hg concentrations from Danish and Greenland peat cores.
    • In-Situ Cosmogenic 14C: Production and Examples of its Unique Applications in Studies of Terrestrial and Extraterrestrial Processes

      Lal, D.; Jull, A. J. T. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Nuclear interactions of cosmic rays produce a number of stable and radioactive isotopes on the earth (Lal and Peters 1967). Two of these, 14C and 10Be, find applications as tracers in a wide variety of earth science problems by virtue of their special combination of attributes: 1) their source functions, 2) their half-lives, and 3) their chemical properties. The radioisotope, 14C (half-life = 5730 yr) produced in the earth's atmosphere was the first to be discovered (Anderson et al. 1947; Libby 1952). The next longer-lived isotope, also produced in the earth's atmosphere, 10Be (half-life = 1.5 myr) was discovered independently by two groups within a decade (Arnold 1956; Goel et al. 1957; Lal 1991a). Both the isotopes are produced efficiently in the earth's atmosphere, and also in solids on the earth's surface. Independently and jointly they serve as useful tracers for characterizing the evolutionary history of a wide range of materials and artifacts. Here, we specifically focus on the production of 14C in terrestrial solids, designated as in-situ-produced 14C (to differentiate it from atmospheric 14C, initially produced in the atmosphere). We also illustrate the application to several earth science problems. This is a relatively new area of investigations, using 14C as a tracer, which was made possible by the development of accelerator mass spectrometry (AMS). The availability of the in-situ 14C variety has enormously enhanced the overall scope of 14C as a tracer (singly or together with in-situ-produced 10Be), which eminently qualifies it as a unique tracer for studying earth sciences.
    • In-Situ Radiocarbon Production by Neutrons and Muons in an Antarctic Blue Ice Field at Scharffenbergbotnen: A Status Report

      van der Borg, K.; van der Kemp, W. J. M.; Alderliesten, C.; de Jong, A. F. M.; Lamers, R. A. N.; Oerlemans, J.; Thomassen, M.; van de Wal, R. S. W. (Department of Geosciences, The University of Arizona, 2001-01-01)
      In the radiocarbon accelerator mass spectrometry (14C AMS) analysis of gases obtained in a dry extraction from a 52-m Antarctic ice core, we observed 14CO2 and 14CO concentrations decreasing with depth. The concentrations are explained in terms of in-situ production by neutrons and captured muons in ablating ice. The ratio of the 14CO2 concentration to that of 14CO has been found to be constant at 1.9 +/0.3. The ablation rates obtained of 42 +/18 cm.yr-1 and 40 +/13 cm.yr-1 for the neutron and muon components, respectively, are about three times higher than observed from stake readings. The discrepancy may point to an incomplete extraction of the dry extraction method. Using the constant ratio in 14CO2 and 14CO concentrations we correct for the in-situ component in the trapped 14CO2 and deduce an age of 10,300 +/900 BP for the ice core.
    • Influence of the Bomb-Produced 14C on the Radiocarbon Concentration in the Youngest Sediments of Lake Gościąż, Central Poland

      Pawlyta, Jacek; Pazdur, Anna; Goslar, Tomasz; Hałas, Stanisław (Department of Geosciences, The University of Arizona, 2001-01-01)
      This work is a study of changes of the radiocarbon concentration in the youngest part of Lake Gościąż sediments in the calendar time scale during the last 150 years. This period includes the time of the nuclear weapons tests performed in the upper atmosphere in the 1950s, and the 1960s, which caused large release of 14C and 137Cs into the environment. On the basis of this study, the isotope dilution factor for 14C and the exchange time of carbon between the atmosphere and Lake Gościąż was estimated. The chronology of the upper part of the sediments was constructed using many interdisciplinary investigations. Among them, measurements of 137Cs in the sediment were used. An unexpected discrepancy between the previously constructed time scale and that suggested by 137Cs is observed in one of the cases.
    • Late Holocene Climatic Change in the Balkans: Speleothem Isotopic Data from Serbia

      Kacanski, Aleksander; Carmi, Israel; Shemesh, Aldo; Kronfeld, Joel; Yam, Ruth; Flexer, Akiva (Department of Geosciences, The University of Arizona, 2001-01-01)
      A detailed profile of the stable isotopes of carbon and oxygen was obtained from a speleothem (stalagmite) from the Ceremosjna Cave in eastern Serbia. The stalagmite is a low magnesian calcite that did not show any evidence of diagenetic alteration. It was precipitated under isotopic equilibrium conditions from dripping water. The age and rate of deposition was derived from six internally consistent radiocarbon dates. The initial 14C activity was determined to be approximately 80 pMC. The stalagmite appears to preserve a continuous record of calcite deposition from approximately 2300 BP until the present. Oxygen isotopic data, based upon 100 samples, are used to derive the first paleotemperature record for Serbia. A regression analysis of the all the data indicates that over the period of time that the speleothem was deposited there was a general trend of lowering of the average temperature. Superimposed upon this are significant long-term temperature fluctuations. These can be divided into four broader climatic groupings. Going from the oldest times to the present, there are two warm periods separated by a period when the temperatures fell below the temperature trend line. However, the absolute temperatures were generally above those of the more recent period that is generally characterized by the coolest climatic conditions.
    • Major Recent Tectonic Uplift in Iskenderun Bay, Turkey

      Koral, H.; Kronfeld, J.; Avsar, N.; Yanko, V.; Vogel, J. C. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Radiocarbon dating was carried out in the sediment profiles of four marine sediment cores taken from Iskenderun Bay, Turkey. The bay is quite shallow in the present day, and a previous tectonic study had considered that the bay floor might have been subsiding. However, this cannot be so, for the 14C ages would thereby lead to the apparent paradox of normal marine sedimentation having taken place during times when glacio-eustatic sea level lowering would have exposed the bay floor. Rather, we conclude that the floor of Iskenderun Bay on the whole has been experiencing rapid uplift since the end of the Last Glacial, due to a combination of tectonic factors linked to the compression between the Anatolian and African plates.
    • Measurement of Radiocarbon Content in Leaves from Some Japanese Sites

      Muraki, Yasushi; Masuda, Kimiaki; Arslanov, K.; Toyoizumi, Hiroaki; Kato, Masataka; Naruse, Yukiko; Murata, Takuya; Nishiyama, Tohru (Department of Geosciences, The University of Arizona, 2001-01-01)
      We have measured radiocarbon contents in leaves collected from 15 sites in Japan, including mountain areas and big city areas for last three years. Comparing the radiocarbon contents in various areas, high 14C concentrations (80-100‰ as δ14C) are seen for the leaves from the mountain and country sites. On the contrary, low concentrations (5-40‰) were observed for the leaves from city region, especially near the road with heavy traffic. These results indicate that the atmosphere of the mountain and country sites in Japan is still clean but the CO2 gas coming from fossil non-radioactive carbon significantly pollutes the atmosphere of the city sites. The value of δ14C for the mountain areas implies that 14C produced by nuclear bomb test in 1960s still remains. The decrease of δ14C at heavy traffic sites in Tokyo is consistent with the increase of CO2 concentration in the atmosphere assuming that almost all CO2 gas in this region originates from the fossil fuel.
    • New Chronological Frame for the Young Neolithic Baden Culture in Central Europe (4th Millennium BC)

      Wild, Eva Maria; Stadler, Peter; Bondár, Maria; Draxler, Susanne; Friesinger, Herwig; Kutschera, Walter; Priller, Alfred; Rom, Werner; Ruttkay, Elisabeth; Steier, Peter (Department of Geosciences, The University of Arizona, 2001-01-01)
      The Baden Culture is a widely spread culture of the Young Neolithics in east-central Europe. In southeast Europe, several parallel cultures are found at different places. The main innovations in east-central Europe associated with the Baden Culture were traditionally thought to originate in southeast Europe, Anatolia, and the Levant. However, in recent years, doubt about this theory has arisen among archaeologists. Here, we try to contribute to this question by increasing the radiocarbon data set available for the Baden Culture. Thirty-two age determinations of samples from different sites assigned to the Baden Culture were performed by accelerator mass spectrometry (AMS) 14C dating. The new data were combined with previously published 14C dates. Data from the individual cultural phases of the entire Baden period and the parallel cultures in southeast Europe (Sitagroi, Cernavoda, and Ezero) were analyzed by sum calibration. Comparison of the results indicates that the southeastern cultures cannot be synchronized with the Boleráz period, the early phase of the Baden Culture. It seems that these cultures were parallel to the Baden Classical period. This finding, which has to be verified by more data from the southeastern cultures, contradicts the theory of the east–west spreading of these cultures.
    • New Data on Chronology of Landscape-Paleoclimatic Stages in Northwestern Russia During the Late Glacial and Holocene

      Arslanov, Kh A.; Savelieva, L. A.; Klimanov, V. A.; Chernov, S. B.; Maksimov, F. E.; Tertychnaya, T. V.; Subetto, D. A. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Two lake and bog sediments have been thoroughly studied using palynological and radiocarbon dating methods. These are the Lembolovskoye Lake section located in the southern part of the Karelian Ithmus and the Mshinskoye bog section located in the southwestern part of the Leningrad province. The data obtained allow us to reconstruct the main features of the vegetation cover evolution, the chronology for the appearance and a real distribution of the main arboreal species from the south of the Leningrad province to the north, and to construct curves of the paleoclimate parameter changes for the area under study. Thirty-six 14C dates were obtained for the Lembolovskoye Lake section (7 m thick). According to those dates, the organic gyttja formation in the lake began 9870 +/170 BP. Spore-pollen spectra with high percentage of herbs, arborescent, and shrub-birch dated back to the Younger Dryas were found out in clay layers at a depth of 6.5 m. An appearance of spruce and alder pollen is dated at 6860 +/120 and 7510 +/150 BP, respectively. The maximal percentage of broad-leaved species falls on the first half of the Atlantic (AT-1). Thirty-two dates were obtained for the Mshinskoye bog section (6 m thick): from 60 +/70 to 9520 +/170 BP (the last date fixed the beginning of peat formation); 12 palinozones from the Preboreal to the Subatlantic were recognized there. The spruce and alder pollen began to appear 7520 +/110 and 7670 +/130 BP, respectively. The maximal amount of broad-leaved species is observed at 4690 +/80 BP. The detailed reconstruction of changes in vegetation communities during the Late Glacial and Holocene was correlated with paleoclimatic characteristics, which have been reconstructed for the section under study by using the information from a statistical method of spore-pollen data processing.
    • New Radiocarbon Dates of the North Asian Steppe Zone and its Consequences for the Chronology

      Göersdorf, Jochen; Parzinger, Hermann; Nagler, Anatoli (Department of Geosciences, The University of Arizona, 2001-01-01)
      The chronological problems of the Steppe zone have been under intensive investigation during the last years but no generally accepted chronological system existed up to now. We present new radiocarbon dates of samples from several excavation sites. The dates allow a comparison of the Bronze Age development in the Siberian Steppe Zone with other neighboring regions.
    • Paleoenvironment in Dae-Am San High Moor in the Korean Peninsula

      Yoshioka, T.; Lee, J. Y.; Takahashi, H. A.; Kang, S. J. (Department of Geosciences, The University of Arizona, 2001-01-01)
      We discuss paleoenvironmental changes at the Dae-Am San high moor, located near the Demilitarized Zone at 38 degrees N. This area has been reported to be the only high moor in the Korean peninsula. The 14C age of the bottom sediment (75-80 cm in depth) at this site is about 1900 BP. Since the radiocarbon ages for the intervals at 50-55 cm and 75-80 cm were almost the same, we conclude that the deep layers (55-80 cm) in the high moor were all part of the original soil. Low organic C and N contents in the deeper layers support this inference. The 50-55 cm layer consists of sandy material with very low organic content, suggesting erosion from the surrounding area. The surface layer (0-5 cm) was measured as 190 BP, and the middle layer (30-35 cm) was 870 BP. The bulk sedimentation rate was estimated to be about 0.4 mm yr-1 for the 0-30-cm interval. The delta-13C value of organic carbon in the sediments fluctuated with depth. The delta-13C profile of the Dae-Am San high moor may be explained by climatic changes which occurred during the Little Ice Age and Medieval Warm Period.
    • Radiocarbon Age of Vertisols and its Interpretation Using Data on Gilgai Complex in the North Caucasus

      Kovda, Irina; Lynn, Warren; Williams, Dewayne; Chichagova, Olga (Department of Geosciences, The University of Arizona, 2001-01-01)
      Radiocarbon dates were analyzed to assess Vertisols age around the world. They show an increase of radiocarbon age from mainly modern-3000 BP in 0-100 cm layer up to 10,000 BP at a depth 100-200 cm. Older dates reflect the age of parent material. The inversion of 14C dates seems to be a frequent phenomenon in Vertisols. A series of new dates of Vertisols from gilgai microhigh, microslope and microlow in the North Caucasus was done in order to understand the nature of this inversion. 14C age in the gilgai soil complex ranges from 70 +/45 BP in the microlow to 5610 +/180 BP in the microhigh. A trend of similar depths being younger in the microslope and microlow was found. We explain this by intensive humus rejuvenation in the microlows due to water downward flow. The older date in the microhigh represents the old humus horizon sheared laterally close to the surface and preserved by impermeable water regime. We explain inversions of 14C age-depth curves by the sampling procedures. In a narrow pit, genetically different parts of former gilgai could easily be as a genetically uniform soil profile. Because of this strong microvariability, Vertisols require sampling in a trench accounting for gilgai elements, even when gilgai are not obvious.
    • Radiocarbon Age Profiles and Size Dependency of Mixing in Northeast Atlantic Sediments

      Brown, Louise; Cook, Gordon T.; MacKenzie, Angus B.; Thomson, John (Department of Geosciences, The University of Arizona, 2001-01-01)
      In recent years, the most common technique for radiocarbon dating of deep-ocean sediments has been accelerator mass spectrometry (AMS) analysis of hand-picked planktonic forminifera (forams). Some studies have exposed age offsets between different sediment size fractions from the same depth within a core and this has important implications when establishing a chronological framework for palaeoceanographic records associated with a particular sediment component. The mechanisms generating the age offsets are not fully understood, a problem compounded by the fact that the fraction defined as "large"varies between different studies. To explore this problem, we dated samples of hand-picked forams from two Biogeochemical Ocean Flux Study (BOFS) cores, for which the presence of an offset between the bulk carbonate and >150 micrometers foraminiferal calcite had already been demonstrated. The presence of a constant age offset between bulk carbonate and coarse fraction material at the two BOFS sites has been confirmed, but the magnitude of the offset is dependent on whether a simple size-separation technique or hand-picking of well-preserved forams is applied. This may be explained if the selection of well preserved forams biases the sample towards those specimens that have spent least time in the surface mixed layer (SML) or have undergone less size selective mixing. Modeling of the 14C profiles demonstrates that SML depth and sediment accumulation rates are the same for both the bulk and coarse sediment fractions, which is consistent with the hypothesis that size-selective mixing is responsible for the age offset.
    • Radiocarbon Ages of Beach Rocks and Late Holocene Sea-Level Changes in the Southern Part of the Nansei Islands, Southwest of Japan

      Omoto, Kunio (Department of Geosciences, The University of Arizona, 2001-01-01)
      Beach rock is a good indicator of the past sea levels, as it is considered to have been formed within the range of intertidal zone. Radiocarbon dates of beach rocks collected from Iriomote Island, Ishigaki Island, and Miyako Island, in the southern part of the Nansei Islands, indicate that the beach rocks were formed between around 4000 BP and 400 BP. Late Holocene sea-level changes were revealed based on the elevations and 14C dates of the beach rocks. The results indicate that the sea level was similar to the present one for at least the past 4000 BP. Isotopic fractionations (delta-13C) of the beach rocks were between +9.4 per mil and -0.8 per mil, suggesting a different origin for calcium carbonate.
    • Radiocarbon AMS Dates for Paleolithic Cave Paintings

      Valladas, H.; Tisnérat-Laborde, N.; Cachier, H.; Arnold, M.; de Quirós, F. Bernaldo; Cabrera-Valdés, V.; Clottes, J.; Courtin, J.; Fortea-Pérez, J. J.; Gonzáles-Sainz, C.; et al. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Advances in radiocarbon dating by accelerator mass spectrometry (AMS) have made it possible to date prehistoric cave paintings by sampling the pigment itself instead of relying on dates derived from miscellaneous prehistoric remains recovered in the vicinity of the paintings. The work at the Laboratoire des Sciences du Climat et de l’Environnement (LSCE) concentrated on prehistoric charcoal cave paintings from southern France and northern Spain. In most caves, pigment samples were collected from several paintings, and in some instances the sample size allowed for multiple independent measurements on the same figure, so that the coherence of the calculated dates could be tested. Before being dated, each specimen was subjected to a thermal treatment preceded by an acid and basic treatment of intensity commensurate with the sample size. Nine bison drawings from three caves in the Cantabrian region of Spain—two from Covaciella, three from Altamira, and four from El Castillo—were sampled and dated. The 27 dates fell between 13,000 and 14,500 BP, allowing us to attribute the drawings to the Magdalenian period. The 24 dates for 13 drawings in the Cosquer cave indicated two distinct periods of painting activity—one around 28,000 BP and the other around 19,000 BP. The Chauvet cave paintings turned out to be the oldest recorded to date, as five dates fell between 32,000 and 31,000 BP. After discussing the sample preparation protocol in more detail, we will discuss the ages obtained and compare them with other chronological data.
    • Radiocarbon as a Tool for Modeling the Diachronic Analysis of the Occupation Phases at the Velzeke Site (Belgium)

      Van Strydonck, Mark; De Mulder, Guy; Deschieter, Johan (Department of Geosciences, The University of Arizona, 2001-01-01)
      The oldest traces of Velzeke go back to the Late Bronze Age and Early Iron Age, followed by a Gallo-Roman settlement and a later medieval village. Although the excavations document the history of the site in general, radiocarbon was used to clarify the successive phases within each feature. The results showed that the ditches at the Roman settlement and the neighboring temple area were already used during the Late Iron Age. The filling up of the ditches could be 14C correlated to a Gallo-Roman occupation phase. The oldest Christian cemetery at the site of the medieval church predates the construction of an important Carolingian stone building (9th to 10th centuries.). The stratigraphically lowest sediments of the ditches, surrounding the Carolingian church, are synchronous with the latest fill of the Iron Age ditch. According to historical and toponymical sources the area of the Iron Age ditch becomes at that time part of a medieval agricultural field system.
    • Radiocarbon Chronology of the Earliest Neolithic Sites in East Asia

      Kuzmin, Yaroslav V.; Keally, Charles T. (Department of Geosciences, The University of Arizona, 2001-01-01)
      The radiocarbon age of the earliest pottery from Russian Far East-Gromatukha and Osipovka cultures-is between around 13,300 BP and around 10,400 BP. This shows that the Amur River basin was one of the centers of origin of pottery in East Asia, at the end of the Pleistocene. Today, there are three areas within East Asia with pottery-associated 14C dates between around 14,000 BP and 13,000 BP—Southern China, the Japanese Isles, and Russian Far East.