• 13C Variation in Limestone on an Aquifer-Wide Scale and Its Effects on Groundwater 14C Dating Models

      Muller, A. B.; Mayo, A. L. (American Journal of Science, 1986-01-01)
      In modeling the initial 14C activity of ground waters, the delta-13C of marine limestone is taken conventionally to vary little about 0 per mil PDB. This variation was found to be 6.28 per mil in samples taken over intervals from 10^-2 to 1^5 meters in the Mooney Falls Member of the Redwall Limestone in northern Arizona. Such a variation will cause appreciable variability in the results of all four initial activity models tested. The variability, due primarily to a numerical instability in the models dependent on this parameter, can introduce significant uncertainty into groundwater "age" calculations.
    • 14C Dating of Calcareous Tufa from Different Environments

      Pazdur, Anna; Pazdur, Mieczysław F. (American Journal of Science, 1986-01-01)
      14C dates of carbonate and organic matter fractions are compared with a series of calcareous tufa samples from selected sites representing different geochemical environments and associated with different bedrocks. Results obtained in this study indicate values of apparent age ranging from 940 +/- 110 yr for calcareous tufas associated with Pleistocene sediments to 2000 +/- 110 yr and even ca 4000 yr for tufas from sites associated with Jurassic or Cretaceous limestone. It was found also that within each of the investigated sites the value of apparent age does not change significantly with the age of the tufa layer.
    • 14C Depth Profiles as Indicators of Trends of Climate and 14C/12C Ratio

      Brown, Robert H. (American Journal of Science, 1986-01-01)
      Composite curvature averages for 14C age depth profiles of deep ocean sediment, continental sediment, and soil each indicate a global trend for 14C age increment per cm depth to increase with 14C age over the range for which a definitive statistical sample is available. The global trend indicated for peat profiles is constant 14C age increment per cm depth over the past 10,000 14C yr. Correlation coefficients between changes in 14C yr/cm and maximum profile thickness contradict compaction as an adequate explanation for the global trend indicated by sediment and soil profiles. This trend must be explained by additional factors such as progressively decreasing contamination from older carbon, increasing cosmic ray intensity, decreasing geomagnetic intensity, diminishing 12C in the active biosphere during profile accumulation, and climate factors affecting the rate of accumulation. The diverse trend of peat profiles may indicate climatic conditions more favorable to peat growth during the earlier portion of the past 10,000 yr.
    • 14C in the Deep Water of the East Atlantic

      Schlitzer, Reiner (American Journal of Science, 1986-01-01)
      The renewal of east Atlantic deep water and its large-scale circulation and mixing have been studied in observed distributions of temperature, silicate, Sigma-CO2, and 14C. 14C variations in northeast Atlantic deep water below 3500m depth are small. Delta-14C values range from -100 per mil to -125 per mil.14C bottom water concentrations decrease from &4C = -117 per mil in the Sierra Leone Basin to Delta-14C = -123 per mil in the Iberian Basin and are consistent with a mean northward bottom water flow. The characteristic of the water that flows from the west Atlantic through the Romanche Trench into the east Atlantic was determined by inspection of theta/Delta-14C and theta/Si02 diagrams. A mean potential temperature of theta = 1.50 +/- .05 degrees C was found for the inflowing water. A multi-box model including circulation, mixing, and chemical source terms in the deep water has been formulated. Linear programing and least-squares techniques have been used to obtain the transport and source parameters of the model from the observed tracer fields. Model calculations reveal an inflow through the Romanche Trench from the west Atlantic, which predominates over any other inflow, of (5 +/- 2) Sv (potential temperature 1.50 degrees C), a convective turnover of (150 +/- 50) years and a vertical apparent diffusivity of (4 +/- 1) cm2/s. Chemical source terms are in the expected ranges.
    • A Study of Errors in 14C Dates of Peat and Sediment

      Olsson, Ingrid U. (American Journal of Science, 1986-01-01)
      It is a well-established fact that 14C dates from lake sediments are usually too old because of contamination with allochthonous material and/or due to discrete reservoir effects. The latter can occur in soft water lakes and may be examined by the 14C measurement of aqueous plants or the carbon dissolved and suspended in the water column. Some plants assimilate CO2 from the sediment. Their 14C activity is then dependent on the sediment accumulation rate and nutrients stored in the root system may also contribute misleading results. If water is filtered through ultra-fine membranes and then treated chemically, several fractions can be isolated for dating. The present study shows that the 14C activity of such fractions varies widely but with the weighted mean indicating an overall deficiency. Even the water from a raised bog evidences a 14C deficiency relative to contemporary atmospheric CO2. Charcoal from an archaeologic site and peat from corresponding layers in a nearby bog have yielded significantly different ages. The fact that the Cladium peat was from a very calcareous area is significant. The risk of contamination by younger root material is also documented.
    • AMS Radiocarbon Dates on Foraminifera from Deep Sea Sediments

      Andree, Michael; Oeschger, Hans; Broecker, Wallace S.; Beavan, Nancy; Mix, Alan C.; Bonani, Georges; Hofmann, Hans Jakob; Morenzoni, Elvezio; Nessi, Marzio; Suter, Martin; et al. (American Journal of Science, 1986-01-01)
      14C ages were determined on samples of foraminifera separated from cores from three areas of the tropical Pacific (Fast Pacific Rise, Oontong Java Plateau, and South China Sea). Analyses were made on four planktonic species and on mixed benthics. The purpose of the multiple analysis on planktonic species is to assess the importance of artifacts resulting from the bioturbation-abundance change couple, from the bioturbation-partial dissolution couple and from redeposition by bottom currents. The goal is to use the benthic-planktonic age difference as a means of establishing changes in deep sea ventilation rate over the past 25,000 years. Results of a part of this work are presented in this paper.
    • Anomalous High 14C Activity Found in Recent Corals from the Philippines

      Willkomm, Horst (American Journal of Science, 1986-01-01)
      The carbonate skeletons of small living corals collected in Spring 1981 from Cebu Island, the Philippines, had 14C activities up to 147% of recent standard. Similarly high values were found in the carbonate structure of three large coral heads, where the 14C content of six penetrating cores was measured. In these corals the activity of the outer parts grown since 1960 reached values as high as 155% (corrected for delta-13C = -25 per mil) while the inner part grown from 1860 to 1950 had values of 106 to 110%. The 14C content of corals should be ca 116% due to the atomic bomb effect and 95% before 1955. The samples were taken from the shore, exposed to tidal waters, so that local contamination is improbable. Organic samples collected from the same region showed normal 14C activity.
    • Archaeologic Sherd Dating: Comparison of Thermoluminescence Dates with Radiocarbon Dates by Beta Counting and Accelerator Techniques

      Johnson, R. A.; Stipp, J. J.; Tamers, M. A.; Bonani, Georges; Suter, Martin; Wölfli, Willy (American Journal of Science, 1986-01-01)
      Sherds can be dated by four independent methods. 14C beta counting on associated material, accelerator mass spectrometry on carbon traces on and within the sherd, thermoluminescence studies on minerals within the sherd, and stylistic form. Age analyses of materials and sherds from several sites are shown in this work. Each technique has its own frequently encountered non-laboratory sources of error. A combination of at least two independent techniques is indispensable for the highest level of confidence.
    • Bomb Produced 14C Content in Tree Rings Grown at Different Latitudes

      Dai, Kai-Mei; Fan, C. Y. (American Journal of Science, 1986-01-01)
      The 14C content in 1961-1967 rings of each of three spruce pines grown at (68 degrees N, 130 degrees W), (47 degrees 30' N, 129 degrees 16' E) and (27 degrees 13' N,100 degrees 20' E) were measured. Delta-14C values of the three specimens rise dramatically from a common level (~250 per mil) in 1961 to their respective maxima, 964 per mil, 909 per mil, and 743 per mil in 1964 and then fall to a common level ~680 per mil in 1967. The observed Delta-14C increase comes most likely from the nuclear bomb test of the USSR at 75 degrees N in 1961, although there were many other tests since the 1950s. The different effects at different latitudes reflect the atmospheric circulation patterns in the stratosphere and the transport of 14C nuclei from the stratosphere to the troposphere.
    • Dating of Holocene Stratigraphy with Soluble and Insoluble Organic Fractions at the Lubbock Lake Archaeological Site, Texas: An Ideal Case Study

      Haas, Herbert; Holliday, Vance; Stuckenrath, Robert (American Journal of Science, 1986-01-01)
      The Lubbock Lake site, on the Southern High Plains of Texas, contains one of the most complete and best-dated late Quaternary records in North America. A total of 117 14C dates are available from the site, determined by the Smithsonian and SMU Laboratories. Of these dates, 84 have been derived from residues (humin) and humates (humic acids) of organic-rich marsh sediments and A horizons of buried soils. Most of the ages are consistent with dates determined on charcoal and wood, and with the archaeologic and stratigraphic record. The dates on the marsh sediments are approximate points in time. Dates from the top of buried A-horizons are a maximum for burial and in many cases are close to the actual age of burial. Dates from the base of the A-horizons are a minimum for the beginning of soil formation, in some cases as much as several thousand years younger than the initiation of pedogenesis. A few pairs of dates were obtained from hurnin and humic acid derived from split samples; there are no consistencies in similarities or differences in these age pairs. It also became apparent that dates determined on samples from scraped trench walls or excavations that were left open for several years are younger than dates from samples taken from exactly the same locations when the sampling surfaces were freshly excavated.
    • Dating Polar Ice by 14C Accelerator Mass Spectormetry

      Andree, Michael; Beer, Jürg; Loetscher, H. P.; Moor, Ernst; Oeschger, Hans; Bonani, Georges; Hofmann, Hans Jakob; Morenzoni, Elvezio; Nessi, Marzio; Suter, Martin; et al. (American Journal of Science, 1986-01-01)
      Results of 14C/12C ratio measurements on CO2 extracted from air bubbles in polar ice are presented. The samples investigated originate from the Dye 3, South Greenland, deep ice core and span approximately the last 10,000 years. The results are calibrated with tree-ring records. The 14C ages are compared with information obtained from seasonal variations of ice-core parameters and rheologic model calculation.
    • Discordant Ages Related to Reservoir Effect of Associated Archaeologic Remains from the Tunel Site, Beagle Channel, Argentine Republic

      Albero, Miguel C.; Angiolini, Fernando E.; Piana, Ernesto L. (American Journal of Science, 1986-01-01)
      Evidence of a tradition of human maritime adaptation was recovered from various sites at Beagle Channel dating back to ca 6000 yr BP. Final occupations date to European settlement in the 19th century. The Túnel site exhibits discontinuous human occupation ranging from 6000 to 500 yr BP, represented by different archaeologic remains in each layer. Associated charcoal, mollusk shells, and Lama guanicoe and Arctocephalus australis bones were dated. Shells and Arctocephalus are consistently older than charcoal, demonstrating the reservoir effect at Beagle Channel. Results encourage further work in the area to evaluate the spatial and temporal magnitude of the effect.
    • Early Slavonic Settlements and Navigation at the Mouth of the Odra River

      Awsiuk, Romuald; Filipowiak, Władyslaw; Goslar, Tomasz; Pazdur, Anna; Pazdur, Mieczysław F. (American Journal of Science, 1986-01-01)
      An attempt is presented to establish an absolute chronology of early Slavonic habitation in the region of the mouth of the Odra River up to the Baltic and to find associations with a series of stave boats and dugouts of different levels of technology and navigation. The methodology of the research project is presented and some conclusions of a general nature are drawn from the results already obtained.
    • Extension of the Holocene Dendrochronology by the Preboreal Pine Series, 8800 to 10,100 BP

      Becker, Bernd; Kromer, Bernd (American Journal of Science, 1986-01-01)
      Holocene tree-ring chronologies have been established for south-central Europe covering the past 11,000 years. The Hohenheim absolute oak chronology extends to 4089 BC. The 14C-calibrated mid-Holocene floating oak master covers a 3181-year period from ca 4045 to 7225 BC. The earliest well-replicated floating oak master (estimated calendar age 7215 to 7825 BC) extends the European oak dendrochronology back to Boreal times. Further extension of the Holocene dendrochronology has been achieved by subfossil oak and pine trees from the Rhine, Main, and Danube Rivers. A 774-year floating series of Preboreal pine has been established. 14C ages range (from younger to older end) from 9200 to 9800 BP. Within this series a major atmospheric 14C variation is indicated, resulting in nearly constant 14C ages (9600 BP) over a period of 370 tree-rings. The European oak and pine tree-ring chronologies cover without major gaps the entire Holocene epoch. Based on the length of the dendro-records, an approximate solar year age of 11,280 years is calculate for the Holocene/Pleistocene boundary. The Preboreal pine forests along the rivers were replaced by mixed oak forests between 9200 and 8800 BP. By linking the earliest oak masters and the Preboreal pine series, the European dendrochronology can be extended up to the end of Late Glacial times.
    • High-Precision 14C Measurement of Irish Oaks to Show the Natural 14C Variations from AD 1840-5210 BC

      Pearson, Gordon W.; Pilcher, J. R.; Baillie, M. G. L.; Corbett, D. M.; Qua, F. (American Journal of Science, 1986-01-01)
      High-precision measurement of dendrochronologically dated Irish oak at bidecade/decade intervals has continued in the Belfast laboratory, extending the 14C data base from ca AD 1840 to 5210 Bc. The dendrochronology is now considered absolute (see Belfast dendrochronology this conference) (Brown et al, 1986) and a continuous detailed curve is presented, showing the natural variations in the atmospheric concentration of 14C over >7000 years. Each data point has a precision of <2.50 per mil, and some 4500 years have now been compared with Seattle, giving excellent agreement. Discussion of this data base and the justification of the claimed accuracy is given together with a comparison of other chronologies. Some of the advantages and limitations of the above are discussed.
    • High-Precision Calibration of the Radiocarbon Time Scale, 3930-3230 Cal BC

      De Jong, A. F. M.; Becker, Bernd; Mook, W. G. (American Journal of Science, 1986-01-01)
    • High-Precision Calibration of the Radiocarbon Time Scale, 500-2500 BC

      Pearson, G. W.; Stuiver, Minze (American Journal of Science, 1986-01-01)
    • High-Precision Calibration of the Radiocarbon Time Scale, AD 1950-500 BC

      Stuiver, Minze; Pearson, Gordon W. (American Journal of Science, 1986-01-01)
    • High-Precision Decadal Calibration of the Radiocarbon Time Scale, AD 1950-2500 BC

      Stuiver, Minze; Becker, Bernd (American Journal of Science, 1986-01-01)
    • High-Precision Radiocarbon Dating of Bristlecone Pine from 6554 to 5350 BC

      Linick, Timothy W.; Long, Austin; Damon, Paul E.; Ferguson, C. Wesley (American Journal of Science, 1986-01-01)
      New results of radiocarbon dating of ca 100 decadal bristlecone pine samples from 6554 to 6084 BC and from 5820 to 5350 BC are presented. Using 3 new 2.5L counters filled to ca 3atm with carbon dioxide, high-precision dating has been performed by this laboratory for more than two years. Demonstration of the precision and accuracy of these counters is presented using +/2 per mil measurements from the Spörer minimum period. For the older samples, +/3 per mil measurements were made using ca 12-day counting times. Results are presented both as 14C age BP vs dendro-year BC, particularly for calibration purposes, and as Delta-14C vs time.