Spatial variation in the MRE throughout the Scottish Post-Roman to late Medieval period: North Sea values (500-1350 BP)

The marine radiocarbon reservoir effect (MRE) occurs as a spatially and temporally dependent variable owing to localized changes in oceanic water composition. This study investigates ΔR values (deviations from the global average MRE whose ΔR = 0) during the period 500–1350 BP for the east coast of Scotland, where a complex estuarine system exists that drains into the semi-enclosed North Sea basin. Due to the availability of suitable archaeological samples, the data set has a distinct Medieval focus that spans the area from Aberdeen in the north to East Lothian in the south. Many of the ΔR values are not significantly different from 0 (the global average), but there are occasional excursions to negative values (max –172 ± 20) indicating the presence of younger water. These values show greater variability compared to other published data for this general region, suggesting that considerable care must be taken when dating marine derived samples from archaeological sites on the east coast of Scotland

Reservoirs and radiocarbon: ¹⁴C dating problems in Myvatnssveit, Northern Iceland

This paper examines 2 potential sources of the radiocarbon offset between human and terrestrial mammal (horse) bones recovered from Norse (~AD 870–1000) pagan graves in Mývatnssveit, north Iceland. These are the marine and freshwater 14C reservoir effects that may be incorporated into human bones from dietary sources. The size of the marine 14C reservoir effect (MRE) during the Norse period was investigated by measurement of multiple paired samples (terrestrial mammal and marine mollusk shell) at 2 archaeological sites in Mývatnssveit and 1 site on the north Icelandic coast. These produced 3 new ΔR values for the north coast of Iceland, indicating a ΔR of 106 ± 10 14C yr at AD 868–985, and of 144 ± 28 14C yr at AD 1280–1400. These values are statistically comparable and give an overall weighted mean ΔR of 111 ± 10 14C yr. The freshwater reservoir effect was similarly quantified using freshwater fish bones from a site in Mývatnssveit. These show an offset of between 1285 and 1830 14C yr, where the fish are depleted in 14C relative to the terrestrial mammals. This is attributed to the input of geothermally derived CO2 into the groundwater and subsequently into Lake Mývatn. We conclude the following: i) some of the Norse inhabitants of Mývatnssveit incorporated non-terrestrial resources into their diet that may be identified from the stable isotope composition of their bone collagen; ii) the MRE off the north Icelandic coast during the Norse period fits a spatial gradient of wider North Atlantic MRE values with increasing values to the northwest; and iii) it is important to consider the effect that geothermal activity could have on the 14C activity of samples influenced by groundwater at Icelandic archaeological sites

Psychoanalytic parent-infant psychotherapy in South Africa : opening ports of entry and flexing the frame.

Parent-infant psychotherapy is a small but growing field in South Africa. Its potential to contribute to mental health services in South Africa is, by contrast, vast. This thesis contributes towards much-needed research on the state of the field in the country and its potential applications across different sectors. Drawing on Daniel Stern’s concept of ports of entry, it is argued that an expansion of ports of entry offers an important integrating tool through which different aspects of parent-infant psychotherapy can be examined and adapted to the South African context. A history of parent-infant psychotherapy in South Africa is offered, together with an analysis of the experiences of current practitioners in the field. These aspects of the thesis draw on interviews with key stakeholders. The dominant context of private practice is then explored through two case study based papers. The first explores the meaning of symptoms in parent-infant psychotherapy. The second introduces the ‘grandmaternal transference’ as an important but under developed port of entry. These different aspects of parent-infant psychotherapy in South Africa are then considered through the prism of ports of entry in order to argue for a flexing of the psychoanalytic frame. Implications for the growth of the parent-infant psychotherapy field in South Africa are considered

Temporal and spatial variations in freshwater 14C reservoir effects: Lake Myvatn, Northern Iceland

Lake Mývatn is an interior highland lake in northern Iceland that forms a unique ecosystem of international scientific importance and is surrounded by a landscape rich in archaeological and palaeoenvironmental sites. A significant Freshwater 14C Reservoir Effect (FRE) has been identified in carbon from the lake at some Norse (c.870-1000 AD) archaeological sites in the wider region (Mývatnssveit). Previous AMS measurements indicated this FRE was ~1500-1900 14C years. Here we present the results of a study using stable isotope and 14C measurements to quantify the Mývatn FRE for both the Norse and modern periods. This work has identified a temporally variable FRE that is greatly in excess of previous assessments. New, paired samples of contemporaneous bone from terrestrial herbivores and omnivores (including humans) from Norse sites demonstrate at least some omnivore diets incorporated sufficient freshwater resources to result in a herbivore-omnivore age offset of up to 400 14C yrs. Modern samples of benthic detritus, aquatic plants, zooplankton, invertebrates and freshwater fish indicate an FRE in excess of 5000 14C yrs in some species. Likely geothermal mechanisms for this large FRE are discussed, along with implications for both chronological reconstruction and integrated investigation of stable and radioactive isotop

Impact of small-scale vegetation structure on tephra layer preservation.

The factors that influence tephra layer taphonomy are poorly understood, but vegetation cover is likely to play a role in the preservation of terrestrial tephra deposits. The impact of vegetation on tephra layer preservation is important because: 1) the morphology of tephra layers could record key characteristics of past land surfaces and 2) vegetation-driven variability in tephra thickness could affect attempts to infer eruption and dispersion parameters. We investigated small- (metre-) scale interactions between vegetation and a thin (<10 cm), recent tephra layer. We conducted surveys of vegetation structure and tephra thickness at two locations which received a similar tephra deposit, but had contrasting vegetation cover (moss vs shrub). The tephra layer was thicker and less variable under shrub cover. Vegetation structure and layer thickness were correlated on the moss site but not under shrub cover, where the canopy reduced the influence of understory vegetation on layer morphology. Our results show that vegetation structure can influence tephra layer thickness on both small and medium (site) scales. These findings suggest that some tephra layers may carry a signal of past vegetation cover. They also have implications for the sampling effort required to reliably estimate the parameters of initial deposits

Degrees of success : evaluating the environmental impacts of long term settlement in South Iceland.

This paper focuses on the occupation and landscape history of Dalur and Mörk, two areas of long-term settlement in the Eyjafjallahreppur district of southern Iceland. The aim is to illustrate the importance of evaluating not only farm occupation and abandonment, but also to assess the complexities of the environmental interactions of long-term settlements. Environmental records are assessed using data from 50 sediment profiles, constrained by tephrochronology, located in the farm infields (tún) and outfields (hagi). This record indicates that despite similar outward appearances today, the environs of Dalur and Mörk have experienced different histories of environmental change over the last 1000 years. At least 14 subsidiary settlements were at one time or another established within Dalur, or were dependent on the Church farm there. Ten of these settlements were subsequently abandoned and sediment accumulation rates, a proxy indicator of erosion, remained low, indicating restricted local human impact. We conclude that this illustrates the importance of access and rights to additional resources out with the principal farm. In addition, much of the immediate environs of the main farm site was probably un-wooded at the time of settlement, so the total degree of vegetative change was limited. In contrast, palaeoenvironmental data indicates that the environs of Mörk were extensively wooded at the time of Landnám, but this woodland was rapidly cleared and this was followed by several centuries of landscape instability. In a cultural contrast, the landholdings of Mörk experienced less subdivision with a total of only five dependent farms established across the land belonging to three main farms (all of which had chapels). From the early 10th to 14th centuries there was significantly enhanced erosion within the Mörk landholdings, but this stabilised and the principal farms endured and to form sites of long-term settlement. The ownership of additional resource rights, including woodland further up-valley, may have made the crucial contribution to long term endurance

Soil moisture, stressed vegetation and the spatial structure of soil erosion in a high latitude rangeland

Funding: Research was supported by a NERC PhD studentship (ref: NE/L002558/) to Polly Thompson and a World-Leading Scholarship, funded by St Leonard’s Postgraduate College, University of St Andrews, to Georg Kodl.Soil erosion has been a persistent problem in high-latitude regions and may worsen as climate change unfolds and encourages increased anthropogenic exploitation. We propose that soil moisture is likely to shape future erosion trends, as moisture stress reduces the capacity of vegetation cover to retard erosive processes. However, the spatial variability of soil moisture in high-latitude soils—and the ways in which this variability drives the spatial distribution of erosion features—is poorly understood. We addressed this knowledge gap with a study of andosol erosion in southern Iceland. Our study used a combination of high-resolution (10 m from eroded terrain. We found lower moisture availability close to existing erosion features: mean volumetric soil moisture content varied from 17% (proximal to erosion patch) to 36% (distal to erosion patch). We also found that variability in soil moisture decreased with distance from eroded areas: the coefficient of variation (CV) in soil moisture varied from 0.33 (proximal to erosion patch) to 0.13 (distal to erosion). Our findings indicate that the margins of erosion patches have a stressful soil environment due to exposure to the atmosphere. The vegetation in these locations grows less vigorously, and the exposed soil becomes more vulnerable to erosion, leading to erosion patch expansion and coalescence. If these conditions hold more generally, they may represent a feedback mechanism that facilitates the lateral propagation of soil erosion in high-latitude regions.Publisher PDFPeer reviewe

Settlement history, land holdings and landscape change, Eyjafjallahreppur, Iceland

In this paper we focus on a region in south Iceland and assess the confidence with which it is possible to determine the changing patterns of settlement history for a region and relate it to contemporaneous land boundaries. For a geographically coherent group of up to 38 possible farm sites in the northern and western part of Eyjafjallahreppur, south Iceland, the timing of occupation and abandonment is assessed. In addition, boundaries of landholdings, probable status and inter-site relationships are identified. Currently only 10 sites are occupied. There is some uncertainty over the location of the earliest settlements, but after the 11th century, successful principle farm sites such as Dalur, Seljaland and Mörk remain in the same locations. As a result, recent data on landholdings combined with a knowledge of the form of landholding sub-division, offers insights into pre-modern times, with some data relevant to medieval times. An ‘abandoned frontier’ exists in the inland area of Þórsmörk, but abandonment is not restricted to the uplands; it has occurred throughout the region. Most desertion occurred before the cold phases of the Little Ice Age in the 18th century. Overall, much farm desertion can be attributed to landscape destruction as a result of river migration, but it is also biased towards small dependent farms often established for social reasons (such as the property requirement for marriage) and evidently insufficiently resourced for long term success in a changing physical environment

Tephra transformations: variable preservation of tephra layers from two well-studied eruptions

Financial support was provided by the National Science Foundation of America through grant 1202692 ‘Comparative Island Ecodynamics in the North Atlantic’, and grant 1249313 ‘Tephra layers and early warning signals for critical transitions’ (both to AJD).Volcanologists often use terrestrial tephra layers to reconstruct volcanic eruptions. However, the conversion of fresh tephra deposits into tephra layers is poorly understood. To address this knowledge gap, we surveyed tephra layers emplaced by the 1980 eruption of Mount St Helens, USA (MSH1980) and the 1947 eruption of Hekla, Iceland (H1947). We compared our measurements with observations made shortly after the 1947 and 1980 eruptions, to calibrate the subsequent transformation of the tephra deposit. We expected the tephra layers to retain the broad characteristics of the original deposits, but hypothesized a) changes in thickness and mass loading due to re-working, and b) positive correlations between thickness and vegetation density. We observed some systematic changes in tephra layer properties with distance from the vent and the main plume axis. However, the preservation of the layers varied both between and within our survey locations. Closed coniferous forest appeared to provide good conditions for the preservation of the MSH1980 tephra, as expected; preservation of the H1947 deposit in sparsely vegetated parts of Iceland was much more variable. However, preservation of the MSH1980 deposit in sparsely vegetated areas of eastern Washington State was also excellent, possibly due to biocrust formation. We concluded that the preservation of tephra layers is sensitive to surface conditions at the time of the eruption. These findings have implications for the reconstruction of past eruptions where eruption plumes span regions of variable surface cover.PostprintPeer reviewe