A radiocarbon database for Scottish archaeological samples

For the majority of dating laboratories and their respective user communities, the journal Radiocarbon is no longer regarded as the medium for primary publication of radiocarbon measurements. In compliance with editorial policy, the emphasis has long since moved towards the publication of research papers on technological enhancements and applications of C-14 as well as other cosmogenic isotopes and this has left a requirement for an alternative medium for the publication of date lists per se.In the late 1980s, an International Radiocarbon Data Base was proposed by Renee Kra (then the managing editor) but limitations in computer and communications technologies together with the inevitable financial implications meant that this timely concept could not be taken to completion. In the last year, we have taken advantage of the development of the worldwide web to compile a database of C-14 age measurements of a Scottish archaeological nature which can be found at the web address http://www.historic-scotland.gov.uk/

Is comparability of C-14 dates an issue?: A status report on the fourth international radiocarbon intercomparison

For more than 15 years, the radiocarbon community has participated in a series of laboratory intercomparisons in response to the issue of comparability of measurements as perceived within the wider user communities (Scott et al. 1990; Rozanski et al. 1992; Guiliksen and Scott 1995; Scott et al. 1997).<br/> In this report, we provide an update on the current C-14 laboratory intercomparison and reflect on future issues linked to the laboratory intercomparison program, not least those resulting from a significant growth in the number of accelerator mass spectrometry (AMS) facilities providing routine dating of small samples (milligram size)

Implications for the dating of Wisconsinan (Weichselian) late-glacial events of systematic radiocarbon age differences between terrestrial plant macrofossils from a site in SW Ireland

AMS radiocarbon dates were obtained from Salix herbacea leaves, Carer seeds, and bulk organic detritus from a lake sediment profile of Wisconsinan (Weichselian) Lateglacial age in SW Ireland. There is a systematic age difference between the dated series from the two types of macrofossils, with ages obtained from Salix herbacea leaves being 900 to 1500 C-14 years younger than those obtained from Carer seeds. The latter tend to be more in accord with dates from the total organic detritus in the lake sediment, although the bulk organic fraction invariably registered the older ages. Intact survival of the fragile Salix leaves indicates that they are unlikely to have been physically transferred within the sediment matrix and/or otherwise reworked from the surrounding catchment, Hence, these macrofossils are the more likely to be contemporaneous with the time of deposition, However, there is no significant correlation between measured C-14 age and depth in the Salix values, which scatter over a range of 700 C-14 years. In contrast, the age/depth relationship for Carer shows a significant reversal, possibly reflecting the redeposition of these macrofossils, and therefore giving radiocarbon ages that are anomalously old, The data have important implications for the dating of lake sediment sequences by AMS radiocarbon measurement of terrestrial plant macrofossils

NERC radiocarbon age measurements determined by radiometric counting 1996-2005

We describe a new compilation of radiocarbon age measurements performed by the NERC Radiocarbon Laboratory that is freely available to access over the World Wide Web. The database contains 1000 14C measurements performed using the liquid scintillation counting method between 1996 and 2005, and further results will be added as the information is compiled. Contextual information including sampling location and the nature of sample material is provided, alongside 14C age results and publications codes. Hypertext links provide access to the original 14C age report associated with the samples, providing additional details. The 14C measurements were originally performed for earth and environmental science NERC projects and are therefore likely to be most relevant to the Quaternary research community

NERC radiocarbon age measurements determined by radiometric counting 1996-2005

We describe a new compilation of radiocarbon age measurements performed by the NERC Radiocarbon Laboratory that is freely available to access over the World Wide Web. The database contains 1000 14C measurements performed using the liquid scintillation counting method between 1996 and 2005, and further results will be added as the information is compiled. Contextual information including sampling location and the nature of sample material is provided, alongside 14C age results and publications codes. Hypertext links provide access to the original 14C age report associated with the samples, providing additional details. The 14C measurements were originally performed for earth and environmental science NERC projects and are therefore likely to be most relevant to the Quaternary research community

Late Quaternary primary tephras in Sacred Lake sediments, northeast Mount Kenya, Kenya

In this paper, a sequence of five Late Quaternary tephras occurring as discrete, well-preserved horizons in lake sediments on the northeastern flank of Mount Kenya are characterised and their ages determined by a combination of high-resolution indirect radiocarbon dating and direct U/Th dating. The grain size characteristics suggest that the tephras are of fairly local origin. These Na-K-rich alkali pyroclasts with a trachytic chemical composition have a highly correlated chemistry and mineralogy, suggesting that they were probably derived from the same genetic series and possibly erupted from a single source vent. Morphological differences are attributed to the peculiar characteristics of each eruption episode. The magma source was probably a small, highly differentiated magma chamber following the olivine basalt-trachyandesite-trachyte-phonolite series, which broadly reflects the Quaternary rock suite of Mount Kenya

A coherent high-precision radiocarbon chronology for the Late- glacial sequence at Sluggan Bog, Co. Antrim, Northern Ireland

Seventy-five radiocarbon dates are presented from Sluggan Bog in Co. Antrim, Northern Ireland. The Holocene peats are underlain by Late-glacial sediments, which also appear to have accumulated largely in a mire environment. The radiocarbon dates, from the Late-glacial and early Holocene part of the profile, were obtained from the humic and humin fractions of the sedimentary matrix, and from plant macrofossils. The last- named were dated by AMS and the sediment samples by radiometric (beta counting) methods. Age-depth models for the three dating series show a very high level of agreement between the two fractions and the macrofossils. No statistically significant difference is found between the beta counting and AMS results. Three tephras were located in the profile, the uppermost of which is in a stratigraphical position Suggestive of the Vedde Ash, but the geochemical and radiocarbon evidence do not support this interpretation. The lower ashes are in the correct stratigraphical position for the Laacher See and Borrobol tephras, attributions substantiated by the radiocarbon evidence, but not by the geochemical data. The Sluggan sequence has generated one of the most internally consistent radiocarbon chronologies for any Late-glacial site in the British Isles, and it is suggested that in future more effort should be devoted to the search for, and analysis of, Late-glacial mire sequences, rather than the limnic records that have formed the principal focus of Late-glacial investigations hitherto

Stable isotopes, radiocarbon and the Mesolithic-Neolithic transition in the Iron Gates

The results of stable carbon and nitrogen-isotope analyses of human bone collagen from the Iron Gates sites of Lepenski Vir, Vlasac and Schela Cladovei are reconsidered in the light of recent developments in stable isotope palaeodietary research and new information on chronology. The revised data have implications for the interpretation of Lepenski Vir and Vlasac, and the timing of the Mesolithic-Neolithic transition in the Iron Gates