Contemporary sediment transport, suspended sediment flux, rates of intertidal sedimentation, and Holocene sedimentation history are assessed for Hamford Water, a small meso-tidal inlet and saltmarsh embayment in Essex, UK. Sediment transport rates are calculated using semi-empirical equations; suspended sediment flux is computed by integration of suspended sediment concentration and velocity across the inlet throat; intertidal sedimentation rates are assessed from monitoring of discrete markers on saltmarsh and mudflat; and Holocene sedimentation is estimated from radiocarbon dating of buried organic layers, sampled using a vibrocorer. Results show a tidal regime typical of ebb-dominated inlets: moderate, ebb-dominant flow (==1 m S·l) in the central ebb channel is matched by similar flood-dominant marginal channel flows. The sediment dynamics are not influenced by any fluvial input; there is negligible fresh water input. The net direction of sediment transport is predominantly ebb-orientated. Coarse sand transport pathways are circulatory and dependent on longshore drift. Sand (D = 0.25 mm) enters at the margins and is expelled in the central ebb channel. Negligible sand is transported further landward than the mouth; intertidal sedimentation relies mainly on levels of suspended sediment. Rates of intertidal sedimentation are spatially variable: tidal creek sedimentation is greater than saltmarsh, with a mean rate of 4.2mm yr"l. Buried organic horizons. radiocarbon dated to 600 years BP, are attributed to reclaimed land levels. Holocene sedimentation rates since 4300 years BP, estimated from 14C dating of shell bands. accord with current estimates of sea-level rise of approximately 1 mm i 1 • The role and evolution of the inlet entrance and ebb tidal delta are seen as critical to the evolution of the embayment as a whole. The interaction of the embayment with the adjacent coastal zone considered essential when fonnulating shoreline management plans. Hamford Water is considered an integral part of the Stour/OrwelllNaze coastal system.

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No / First presented at an August 2001 national meeting of the American Chemical Society, material in this book provides a cross-section of current research in the area of chemistry applied to archaeological questions. Examples are given of the use of analytical methods in the study of a variety of archaeological materials, and inferences that can be made based on data patterns are discussed. Emphasis is on nondestructive testing and new developments in determining an object's age and composition.

Radiocarbon calibration is a fundamental stage of the radiocarbon dating process if meaningful calendar ages are to be derived from samples’ radiocarbon determinations. However, the present limit of direct, non-reservoir-corrected, atmospheric radiocarbon calibration is 12,550 calibrated years before present (Reimer et al. 2009), leaving approximately three quarters of the radiocarbon timescale to be necessarily calibrated via less secure marine records. The sediment profile of Lake Suigetsu, Honshu Island, central Japan, offers an ideal opportunity from which to derive an extended, ‘wholly terrestrial’ and continuous record of atmospheric radiocarbon back to the limits of radiocarbon detection (circa 60,000 years before present). The presence of well-defined, annually-deposited laminae (varves) throughout this extended time period provides an independent, high resolution chronometer against which radiocarbon measurements, performed upon plant macrofossil samples retrieved from the sediment column, can be directly related. This site was first exploited for radiocarbon calibration purposes by Kitagawa and van der Plicht (1998a, 1998b), however, issues pertaining to the reliability of the calendar age scale of this work precluded the widespread uptake of this dataset. The work presented in this DPhil thesis represents a significant contribution to the broader, ‘Suigetsu Varves 2006’ project – an international collaboration centring on the re-coring of Lake Suigetsu, which was undertaken in summer 2006 to improve upon the shortcomings of the previous project and, thereby, to fully exploit the site’s potential for both radiocarbon calibration and multi-proxy palaeoenvironmental study (Nakagawa et al. 2011). This DPhil thesis describes the generation of the revised (‘SG06’) terrestrial radiocarbon calibration dataset from Lake Suigetsu, comprising 647 accelerator mass spectrometry (AMS) radiocarbon determinations, and extending across the complete range of the radiocarbon dating method. Furthermore, visual matching of archive SG93 core sections to the continuous SG06 sediment profile was undertaken, allowing the integration of the ≈ 300 radiocarbon determinations from the original Lake Suigetsu project into a higher resolution (≈ 900 radiocarbon measurements), combined Lake Suigetsu radiocarbon calibration dataset, providing a unique reconstruction of atmospheric radiocarbon across the entire radiocarbon dating timescale.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 43-46). Also available on the World Wide Web.

名古屋大学年代測定総合研究センターシンポジウム報告

タンデトロン加速器質量分析計業績報告

Paleosols contain information about the rates of soil organic carbon turnover when the soil was actively forming. However, this temporal information is often difficult to interpret without tight stratigraphic control on the age of the paleosol. Here we apply ramped pyrolysis/oxidation (Ramped PyrOx) C-14 analyses to evaluate age spectra of transgressive early Holocene paleosols from the Mississippi Delta in southeastern Louisiana, USA. We find C-14 age spectra from soil organic matter (SOM) in both paleosols and overlying basal peats that represent variability in age that is close to, or only slightly greater than, analytical uncertainty of C-14 measurements, despite different sources of carbon with likely disparate ages. Such age spectra have not previously been observed in the sedimentary record. Here they indicate vigorous soil carbon turnover prior to burial, which homogenized C-14 ages within SOM across the entire thermochemical spectrum. The weighted bulk C-14 ages from Ramped PyrOx of paleosols and overlying peats are identical within analytical and process-associated uncertainty, and corroborate C-14 ages from charcoal fragments and plant macrofossils from the overlying peat. The youngest ages from Ramped PyrOx age spectra may also potentially be applied as chronometers for stratigraphic burial ages. Our results suggest rapid turnover (<<300 years) of carbon in these soils relative to input of allochthonous carbon, indicating that the C-14 age of different soil components is decoupled from thermochemical stability and instead reflects vigorous turnover processes. The concurrence of paleosol and peat C-14 ages also suggests that pedogenic processes were linked with the development of coastal marshes, and that the priming effect potentially masked the signal of allochthonous carbon inputs during sea level rise.

The lowland Maya site of Ceibal, Guatemala, had a long history of occupation, spanning from the Middle Preclassic Period through the Terminal Classic (1000 BC to AD 950). The Ceibal-Petexbatun Archaeological Project has been conducting archaeological investigations at this site since 2005 and has obtained 154 radiocarbon dates, which represent the largest collection of radiocarbon assays from a single Maya site. The Bayesian analysis of these dates, combined with a detailed study of ceramics, allowed us to develop a high-precision chronology for Ceibal. Through this chronology, we traced the trajectories of the Preclassic collapse around AD 150–300 and the Classic collapse around AD 800–950, revealing similar patterns in the two cases. Social instability started with the intensification of warfare around 75 BC and AD 735, respectively, followed by the fall of multiple centers across the Maya lowlands around AD 150 and 810. The population of Ceibal persisted for some time in both cases, but the center eventually experienced major decline around AD 300 and 900. Despite these similarities in their diachronic trajectories, the outcomes of these collapses were different, with the former associated with the development of dynasties centered on divine rulership and the latter leading to their downfalls. The Ceibal dynasty emerged during the period of low population after the Preclassic collapse, suggesting that this dynasty was placed under the influence from, or by the direct intervention of, an external power.