Prof Christopher Ramsey

Abstract:

The Marine20 radiocarbon (14C) age calibration curve, and all earlier marine 14C calibration curves from the IntCal group, must be used extremely cautiously for the calibration of marine 14C samples from polar regions (outside ∼ 40ºS–40ºN) during glacial periods. Calibrating polar 14C marine samples from glacial periods against any Marine calibration curve (Marine20 or any earlier product) using an estimate of ΔR, the regional 14C depletion adjustment, that has been obtained from samples in the recent (non-glacial) past is likely to lead to bias and overconfidence in the calibrated age. We propose an approach to calibration that aims to address this by accounting for the possibility of additional, localized, glacial 14C depletion in polar oceans. We suggest, for a specific polar location, bounds on the value of ΔR20(θ) during a glacial period. The lower bound ΔR Hol 20 may be based on 14C samples from the recent non-glacial (Holocene) past and corresponds to a low-depletion glacial scenario. The upper bound, ΔR, representing a high-depletion scenario is found by increasing ΔR Hol 20 according to the latitude of the 14C sample to be calibrated. The suggested increases to obtain are based upon simulations of the Hamburg Large Scale Geostrophic Ocean General Circulation Model (LSG OGCM). Calibrating against the Marine20 curve using the upper and lower ΔR 20 bounds provide estimates of calibrated ages for glacial 14C samples in high- and low-depletion scenarios which should bracket the true calendar age of the sample. In some circumstances, users may be able to determine which depletion scenario is more appropriate using independent paleoclimatic or proxy evidence.

Abstract:

<jats:title>ABSTRACT</jats:title> <jats:p>The IntCal family of radiocarbon (<jats:sup>14</jats:sup>C) calibration curves is based on research spanning more than three decades. The IntCal group have collated the <jats:sup>14</jats:sup>C and calendar age data (mostly derived from primary publications with other types of data and meta-data) and, since 2010, made them available for other sorts of analysis through an open-access database. This has ensured transparency in terms of the data used in the construction of the ratified calibration curves. As the IntCal database expands, work is underway to facilitate best practice for new data submissions, make more of the associated metadata available in a structured form, and help those wishing to process the data with programming languages such as R, Python, and MATLAB. The data and metadata are complex because of the range of different types of archives. A restructured interface, based on the “IntChron” open-access data model, includes tools which allow the data to be plotted and compared without the need for export. The intention is to include complementary information which can be used alongside the main <jats:sup>14</jats:sup>C series to provide new insights into the global carbon cycle, as well as facilitating access to the data for other research applications. Overall, this work aims to streamline the generation of new calibration curves.</jats:p>

Abstract:

Analyses of radiocarbon dates (all corrected for the freshwater reservoir effect) and associated stable isotope values obtained from the skeletal remains of ~560 individuals provide many new insights about Middle Holocene hunter-gatherers (HG) of the Cis-Baikal region, Eastern Siberia. The new radiocarbon evidence clarifies the culture history of the region by defining better the boundaries between the chronological (archaeological periods) and cultural (mortuary traditions) units, as well as our understanding of the transitions between them. Furthermore, differences between the four archaeological micro-regions with regard to the timing and duration of these culture historical units have come into focus for the first time. In terms of dietary patterns, the Early Neolithic foragers of the Angara and Southwest Baikal trended towards a greater reliance on aquatic foods. A similar trend was found in the Late Neolithic Isakovo group on the Angara, while the Late Neolithic Serovo group in the Little Sea trended towards an increased dietary reliance on terrestrial game. In the Early Bronze Age HG, a mosaic of dietary patterns was found: some groups experienced dietary shifts (frequently emphasizing different foods), while other groups displayed stability. Such differences were found even between close neighbours. All these results suggest significant variation in patterns of culture change within and between archaeological periods, mortuary traditions, and micro-regions. Some cultural patterns developed at a quick pace, others much more slowly; some appear to have collapsed rapidly, while others probably went through a more gradual transition to a different pattern. Additionally, this large set of radiocarbon dates allows novel insights into patterns of cemetery use: some seem to have been used continuously, others only sporadically, and some show long periods of disuse. Moreover, some cemeteries of the same mortuary tradition were apparently in use substantially earlier than others were even established. In sum, Cis-Baikal Middle Holocene HG strategies underwent a range of changes not only at the boundaries between relevant culture historical units but also within such units. New insights suggest considerable spatio-temporal variation in the nature, pace, and timing of these developments.

Abstract:

Hunter-gatherer archaeology typically focusses on the details of subsistence strategies and material culture and, in the case of cemeteries, on various aspects of mortuary practices, beliefs, and social differentiation. This paper aims to look rather at patterns of change over time and space in how past hunter-gatherer cemeteries were used from Late Mesolithic to Early Bronze Age (~8600–3500 cal BP) in the Cis-Baikal region of Eastern Siberia. The approach is based on a Kernel Density Estimate methodology applied to 560 radiocarbon dates obtained for individual burials from 65 cemeteries and representing 5 distinct mortuary traditions. This enables a number of different types of analysis to be performed at different scales: (1) It is possible to examine the overall tempo of burial events at each cemetery or a group of cemeteries; (2) Within each cemetery the spatial patterns of the sequence of graves and burials can be analyzed further; (3) It is possible to compare the different cemetery-specific chronologies within the microregional or regional context; and (4) Although tentatively at this time, the spatiotemporal pattern of cemetery use over the whole region can be visualised. The spatiotemporal analysis of individual cemeteries shows that each one had its own pattern, some very distinct and clear in their characteristics, which relate to the role the cemetery played for the local group, and within the microregional or regional population. On the regional scale some broader patterns such as shifts in frequency of burial events between microregions within mortuary traditions are visible. However, at this scale the existing sampling biases require caution in assessment of the results and future fieldwork will help improve the analysis and insights. On the other hand, many of the individual cemeteries have been excavated in full and such comprehensive datasets already provide a range of entirely new and important insights into cemetery use by the Middle Holocene hunter-gatherers of Cis-Baikal.

Abstract:

The FeedSax project combined bioarchaeological data with evidence from settlement archaeology to investigate how, when and why the expansion of arable farming occurred between the 8th-13th centuries in England. It has generated and released a vast, multi-faceted archaeological dataset both to underpin its own published findings and to support further research.