Early researchers of radiocarbon levels in Southern Hemisphere tree rings identified a variable North-South hemispheric offset, necessitating construction of a separate radiocarbon calibration curve ...for the South. We present here SHCal20, a revised calibration curve from 0–55,000 cal BP, based upon SHCal13 and fortified by the addition of 14 new tree-ring data sets in the 2140–0, 3520–3453, 3608–3590 and 13,140–11,375 cal BP time intervals. We detail the statistical approaches used for curve construction and present recommendations for the use of the Northern Hemisphere curve (IntCal20), the Southern Hemisphere curve (SHCal20) and suggest where application of an equal mixture of the curves might be more appropriate. Using our Bayesian spline with errors-in-variables methodology, and based upon a comparison of Southern Hemisphere tree-ring data compared with contemporaneous Northern Hemisphere data, we estimate the mean Southern Hemisphere offset to be 36 ± 27 14C yrs older.
Bayesian chronological modelling is fast becoming the method of choice for the interpretation of radiocarbon dates in archaeological and palaeoenvironmental studies around the world. Although ...software enabling the routine application of the method has been available for more than twenty years, more than half of published models have appeared in the past five years. Unfortunately, the pace of development in statistical methodology has not been matched by the increased care in sample selection and reporting that is required for robust modelling. Barely half the applications considered in this article provide the information necessary to assess the models presented critically. This article discusses what information is required to allow the quality of Bayesian chronological models to be assessed, and provides check-lists for authors, editors and referees, in the hope of improving current practice.
In 2018 Pearson et al. published a new sequence of annual radiocarbon (14C) data derived from oak (Quercus sp.) trees from Northern Ireland and bristlecone pine (Pinus longaeva) from North America ...across the period 1700–1500 BC. The study indicated that the more highly resolved shape of an annually based calibration dataset could improve the accuracy of 14C calibration during this period. This finding had implications for the controversial dating of the eruption of Thera in the Eastern Mediterranean. To test for interlaboratory variation and improve the robustness of the annual dataset for calibration purposes, we have generated a replicate sequence from the same Irish oaks at ETH Zürich. These data are compatible with the Irish oak 14C dataset previously produced at the University of Arizona and are used (along with additional data) to examine inter-tree and interlaboratory variation in multiyear annual 14C time-series. The results raise questions about regional 14C offsets at different scales and demonstrate the potential of annually resolved 14C for refining subdecadal and larger scale features for calibration, solar reconstruction, and multiproxy synchronization.
Sixty years ago, the advent of radiocarbon dating rewrote archaeological chronologies around the world. Forty years ago, the advent of calibration signaled the death knell of the diffusionism that ...had been the mainstay of archaeological thought for a century. Since then, the revolution has continued, as the extent of calibration has been extended ever further back and as the range of material that can be dated has been expanded. Now a new revolution beckons, one that could allow archaeology to engage in historical debate and usher in an entirely new kind of (pre)history. This paper focuses on more than a decade of experience in utilizing Bayesian approaches routinely for the interpretation of 14C dates in English archaeology, discussing both the practicalities of implementing these methods and their potential for changing archaeological thinking.
The Sun sporadically produces eruptive events leading to intense fluxes of solar energetic particles (SEPs) that dramatically disrupt the near-Earth radiation environment. Such events have been ...directly studied for the last decades but little is known about the occurrence and magnitude of rare, extreme SEP events. Presently, a few events that produced measurable signals in cosmogenic radionuclides such as
C,
Be and
Cl have been found. Analyzing annual
C concentrations in tree-rings from Switzerland, Germany, Ireland, Russia, and the USA we discovered two spikes in atmospheric
C occurring in 7176 and 5259 BCE. The ~2% increases of atmospheric
C recorded for both events exceed all previously known
C peaks but after correction for the geomagnetic field, they are comparable to the largest event of this type discovered so far at 775 CE. These strong events serve as accurate time markers for the synchronization with floating tree-ring and ice core records and provide critical information on the previous occurrence of extreme solar events which may threaten modern infrastructure.
A recent study into prescreening techniques to identify bones suitable for radiocarbon dating from sites known for poor or variable preservation (Brock et al. 2007, 2010a) found that the percent ...nitrogen (%N) content of whole bone powder was the most reliable indicator of collagen preservation. Measurement of %N is rapid, requires little preparation or material, and is relatively cheap. The technique reduces the risk of needlessly sampling valuable archaeological objects, as well as saving time and money on their unsuccessful pretreatment prior to dating. This method of prescreening is now regularly used at the Oxford Radiocarbon Accelerator Unit (ORAU). In the original study, linear regression analysis of data from 100 bones from 12 Holocene sites across southern England showed that when 0.76% N was chosen as a threshold, 84% of bones were successfully identified as containing sufficient (i.e. >1%) or insufficient (i.e. <1%) collagen for dating. However, it has been observed that for older, Pleistocene bones the failure rate may be higher, possibly due to the presence of more degraded, short-chain proteins that pass through the ultrafilters used in pretreatment, resulting in lower yields. Here, we present linear regression analysis of data from nearly 600 human and animal bones, antlers, and teeth, from a wide range of contexts and ages, to determine whether the 0.76% threshold identified in the previous study is still applicable. The potential of carbon:nitrogen atomic weight ratios (C:N) of whole bone to predict collagen preservation is also discussed.
Archaeological investigations at Huntsman’s Quarry, Kemerton, south Worcestershire during 1995-6 recorded significant Late Bronze Age occupation areas and field systems spreading across more than 8 ...hectares. Limited evidence for Upper Palaeolithic, Mesolithic, Neolithic and Beaker activity was also recovered together with an Early Bronze Age ring-ditch. Waterholes and associated round-houses, structures and pits were set within landscape of fields and droveways radiocarbon dated to the 12th–11th centuries cal BC. Elements of this field system probably predated the settlement. Substantial artifactual and ecofactual assemblages were recovered from the upper fills of the waterholes and larger pits . The settlement had a predominantly pastoral economy supported by some textile and bronze production. Ceramics included a notable proportion of non-local fabrics demonstrating that the local population enjoyed a wide range of regional contacts. Wider ranging, national exchange networks were also indicated by the presence of shale objects as well as the supply of bronze for metalworking, perhaps indicative of a site of some social status. Together the evidence indicates a small settlement within which occupation of individual areas was short-lived with the focus of the settlement shifting on a regular basis. It is proposed that this occurred on a generational basis, with each generation setting up a new ‘homestead’ with an associated waterhole. The settlement can be compared favorably to those known along the Thames Valley but until now not recognized in this part of the country. Cropmark evidence and limited other investigations indicate that the fields and droveways recorded represent a small fragment of a widespread system of boundaries established across the gravel terraces lying between Bredon Hill and the Carrant Brook. This managed and organized landscape appears to have been established for the maintenance of an economy primarily based on relatively intensive livestock farming; the trackways facilitating seasonal movement of stock between meadows alongside the Carrant Brook, the adjacent terraces and the higher land on Bredon Hill.
A handful of new radiocarbon dates from three Balaton-Lasinja culture graves at the site of Veszprém-Jutasi út in western Hungary form the starting point for formal models for late Lengyel and ...post-Lengyel chronology in that region. The graves date to the later fifth millennium cal BC. They provide the opportunity to put the earlier Copper Age Balaton-Lasinja culture of Transdanubia into its regional and wider context, and to highlight both gradually improving understanding of its character and remaining problems of chronology and classification. The Balaton-Lasinja culture was part of a whole series of regional shifts in settlement and society connected to the end of the Neolithic and the demise of major settlement aggregations which had dominated lifestyles in previous centuries. This study indicates how much further detailed research continues to be needed to get fully to grips with this set of important changes, which run on into the Copper Age. Contrasts are drawn between western and eastern Hungary, and the uncertainties surrounding the chronology of the fourth millennium cal BC, including for the Furchenstich pottery style, are emphasised.
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