The major work involved is the development of a practical and reliable radiocarbon dating laboratory at Ball State University. The method involved in determining the age of an organic sample, such as wood, peat, bone, or shell, is a carbon to benzene conversion procedure, followed by a liquid scintillation counting technique. The procedure involves producing; lithium carbide at 9000 C from our carbon sample, and then adding distilled water at room temperature to generate acetylene gas. Using a vanadium pentoxide on alumina catalyst, the acetylene is trimerized to benzene. The benzene is used in the liquid scintillation counter to determine the radiocarbon content. The age of a sample is then calculated from the ratio of carbon-14 to carbon-12, as found through the counting technique.Ball State UniversityMuncie, IN 47306

第23回名古屋大学年代測定総合研究センターシンポジウム平成22(2010)年度報告

第23回名古屋大学年代測定総合研究センターシンポジウム平成22(2010)年度報告

Plasma oxidation, an alternative to combustion, is shown to be a non-destructive method for obtaining radiocarbon dates on perishable organic artifacts. Electrically excited oxygen gently converts organic carbon to carbon dioxide. Radiocarbon measurements are then performed using accelerator mass spectrometry. Because only sub-milligram amounts of material are removed from an artifact over its exposed surface, no visible change in fragile materials has been observed, even under magnification. Materials in this study include: Third International Radiocarbon Intercomparison (TIRI) sample B (Belfast pine); Fourth International Radiocarbon Intercomparison (FIRI) optional samples; six different materials from a naturally mummified baby bundle from southwest Texas; and peyote from Shumla Caves, Texas, and Cuatro Ci??negas, Mexico. Continuing previous research in the Rowe laboratory, a primary application of plasma oxidation has been its use to date rock art at archaeological sites around the world. This dissertation includes dates for: Toca do Serrote da Bastiana, Brazil; Ignatievskaya Cave, Russia; partially buried megalithic monuments, Spain; Arnold/Tainter Cave, Wisconsin; and Little Lost River Cave No. 1, Idaho.

No description available.

The Bahamian Archipelago is one of the few locations in the world where ooid formation is actively occurring. Ooid cortices from six locations in the region were incrementally dissolved and analyzed for 14C, δ18O, δ13C, Mg/Ca and Sr/Ca ratios. Ooids were examined under SEM after each step in the incremental analyses to characterize the nature of dissolution. Radiocarbon dating indicates that surface ooids began forming across the Archipelago between 1000 and 2800 yr BP and continue to form today. The ooids have the same pattern of microboring alteration across the region. The surface and outer cortex of the ooids are punctuated with unfilled microborings, whereas the inner cortex contains two morphologies of aragonite cement filling the microborings. The two morphologies of cement form in association with two different species of cyanobacteria, one is Solentia sp. the other is interpreted to be Hyella sp.. The chemistry of ooids from across the region is remarkably similar. δ18O and δ13C values for all samples vary directly, having a slope of approximately 1. The outer cortex has low δ18O and δ13C values of -3.4‰ and 0.2‰ respectively, whereas the δ18O and δ13C values of the inner cortex are high with values of 1.9‰ and 6.8‰ respectively. The presence of aragonite cement in microborings in the inner cortex increases the overall isotopic composition of both oxygen and carbon in the ooid, causing it to appear close to equilibrium with seawater. The isotopic variation in δ18O and δ13C within the cortex can be characterized as a mixing line between the low values in the unaltered ooid laminae and the aragonite cement in the microborings. The most exterior portion of the ooid has very high Mg/Ca values and is interpreted as an amorphous calcium carbonate (ACC) coating. There are two other phases in the cortex, both being aragonite. The outer cortex has a higher Mg/Ca ratio and lower Sr/Ca ratio than the inner cortex. This difference in chemistry is a result of the presence of aragonite cement in the inner cortex. Stable isotopic and trace element results coupled with SEM investigations indicate that microbes do not play a role in ooid formation, but instead alter the texture and chemistry of ooids after they have formed. This alteration occurs throughout the entire shoal region. A new model of ooid formation is proposed whereby a veneer of ACC precipitates on an ooid while it is at the sediment-water interface (the active phase). This veneer of ACC later recrystallizes to aragonite needles, possibly nucleating on organic material and a new cortex layer is formed. Observations from this study lead to a deeper understanding of the chemical processes involved in ooid genesis, which allows for a better understanding of paleoenvironments hosting ooid formation. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2009-01-27 13:29:42.765

第23回名古屋大学年代測定総合研究センターシンポジウム平成22(2010)年度報告

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 165-166). / xii, 166 leaves, bound col. ill., maps 29 cm

Abstract This thesis deals with the Holocene development of palsa mires in continental Europe, especially permafrost dynamics and its consequences on vegetation succession and peat accumulation. Peat deposits of four permafrost mires in boreal and subarctic northeastern European Russia and in northern oroboreal Finland have been studied using plant macrofossil analysis, (AMS) radiocarbon dating, dry bulk density and carbon content measurements. In addition, preliminary results are available from another palsa mire in northeastern European Russia. Modern vegetation has been investigated to support the interpretation of fossil plant assemblages. Earlier literature on vegetation, stratigraphy and dating of permafrost mires in Europe has been reviewed. The vegetation of palsa mires in general is well known. As a rule, palsas are dry ombrotrophic habitats, surrounded by wet flarks of variable trophic levels. There is a lack of information about vegetation in different small-scale habitats within palsa mires, which would have been useful when studying the permafrost-vegetation relationship. Although no functional indicator species of permafrost have been found, permafrost dynamics in peat stratigraphy can often be detected with high degree of probability based on changes in vegetation. Some plant assemblages and vegetation successions are typical on permafrost, while many species rarely grow on or near to permafrost. Relatively sudden changes between dry and wet mire environments and continuously dynamic conditions are good signs of permafrost impact. Also gradual changes towards drier conditions may be caused by permafrost; in these cases the timing of first permafrost aggradation is more difficult to ascertain and can usually be pronounced only in terms of maximum and minimum ages. Changes in peat accumulation rates and even hiatuses in stratigraphy are additional tools to support the interpretation on permafrost history at the studied sites. Dry organic matter and carbon accumulation rates for different developmental stages are calculated for the five studied mires. From earlier studies this information is not available. Accumulation rates in the permafrost environment are very variable: from zero or negative rates in old palsas to as high as 100 gC/m2yr in incipient palsas. On moist plateau palsas, permafrost flarks and in unstable permafrost conditions, accumulation continues at low to moderate rates. Thermokarst processes result in decomposition of former peat deposits with important consequences for the ecosystem carbon balance, especially in plateau palsa mires. Radiocarbon datings are available from 27 permafrost mires in continental Europe; only 5 of these are situated in Russia. Many of the published dates cannot be considered reliable as dating permafrost aggradation. Based on limited material, permafrost started to develop at latest about 3000 BP in mires of northern Russia and 2500 BP in Fennoscandia. Older permafrost formation is suggested for a few sites, but the evidence is insufficient to confirm this interpretation. The oldest preserved palsas are ca. 2500–2000 14C years old. Most of the modern palsas are less than 600 14C years old. Permafrost aggradation follows the major climate development in the Holocene, with formation being most active during the coldest stages. Global warming is expected to greatly affect the Arctic in the near future, which would imply significant changes in ecosystem functioning and carbon balance of permafrost mires. This study contributes to the understanding of the possible impacts of climate change on these ecosystems using paleoecological techniques.

Archaeologists describe the Uinta Fremont (A.D. 0 – 1300) as a mixed foraging-farming society that underwent a dramatic social change from A.D. 700 – 1000. Researchers observe through different architectural styles and subsistence activity a change from large, aggregated settlements to more dispersed and defensively oriented villages and hamlets. The Ideal Free Distribution (IFD) model provides an explanatory framework through which to interpret these changes. IFD predicts the order in which people or animals will occupy habitats based on a habitat’s relative suitability and suggests hypothetical behaviors that people or animals might engage in to improve or maintain the relative suitability of a habitat. One prediction of IFD is that behaviors indicating resource competition will become more frequent when population density increases. I test whether this hypothesis explains changes in storage features by considering storage behavior as a manifestation of resource competition, and I investigate whether storage feature frequency correlates with periods of Fremont population increases and paleoenvironmental degradation. These tests explain aspects of Fremont culture change and suggest future research possibilities. Storage feature frequency, representing resource competition, remains low from A.D. 0 – 700, suggesting that the habitats could absorb growing Fremont populations. After A.D. 700, however, resource competition rose and remained high, a condition that likely spurred the defensive architecture and dispersed settlements that became increasingly common after A.D. 1000. The successes and limitations of applying IFD to the archaeological record point the way toward future uses of the model to investigate settlement spacing and reaffirm the use of radiocarbon data in archaeological science.