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Papers by Sarah-Jane Clelland

Objective: To present the initial experience on lumboscopic radical nephrectomy in our hospital. ... more Objective: To present the initial experience on lumboscopic radical nephrectomy in our hospital. Materials and methods: We reviewed the clinical files of 18 patients who underwent a radical lumboscopic nephrectomy at

Physics of the Earth and Planetary Interiors, 2012

Lake sediments can play an important role in understanding and reconstructing temporal characteri... more Lake sediments can play an important role in understanding and reconstructing temporal characteristics of the geomagnetic field, as they potentially offer near continuous high-resolution archives of magnetic information extending throughout the Holocene. To date lake sediment geomagnetic data has typically been excluded from British archaeomagnetic secular variation curves (SVC) due to uncertainties with the acquisition of magnetisation by lake sediments. This paper presents the argument that, with regards to British datasets, the real problem lies with poor chronological control and sets out to illustrate that with British archaeomagnetic data some progress has been made. The results indicate that it is not currently possible to resolve secular variation on a time scale of $100 years from published British lake sediment data but more success has been made with data from archaeological sediments. This level of detail has been considered necessary for the incorporation of lake sediment data into the British archaeomagnetic dataset, as the ability to resolve short-term geomagnetic changes is critical for the integration of any dataset into the British SVC. As the latter is predominantly employed to date archaeological architecture and artefacts requires that it has the ability to resolve changes over timescales relevant to human lifetimes. Using currently available data this retrospective critique confirms that, in archaeological sediments, depositional and thermoremanent magnetisation can record the same direction over the same time interval.

Archaeometry, 2013

To obtain accurate results in the RHX dating of ceramics, it is essential that the RHX measuremen... more To obtain accurate results in the RHX dating of ceramics, it is essential that the RHX measurements are continued until the rate of mass gain is constant with (time) 1/4. In this paper, we discuss how the initial stages of mass gain are affected by the specific surface area (SSA) of the ceramic material. The paper provides guidance on experimental protocols to avoid dating results being distorted by relatively early-time mass gain data.

Applied Geochemistry, 2006

The authors report a preliminary study of the light stable isotopic (δD, δ13C and δ18O) values fo... more The authors report a preliminary study of the light stable isotopic (δD, δ13C and δ18O) values for bulk archaeological birch bark tars, over a geographical (e.g. Greece to Norway) and chronological (9500–3000BP) range. For δ13C an increase in fractionation with increase in latitude is observed in samples from Greece which are less depleted than those from northern Europe. There is no clear difference between the samples from northern Europe. There is no apparent trend in δ13C value with the 14C age of the sample. Due to biosynthetic fractionation all the samples are significantly depleted in 2H and enriched in 18O relative to the global meteoric water line. This study indicates that archaeological birch bark tar from Greece can be distinguished from those of northern Europe; this separation is probably based on the extreme geographical range of the samples examined here. But this does provide evidence that the birch bark tars were probably made locally rather than traded.

ABSTRACT This chapter describes two new investigations into the use of several different scientif... more ABSTRACT This chapter describes two new investigations into the use of several different scientific methods - magnetic methods, trace element, mineralogical and isotopic analyses - to characterise steatite sources from Shetland. Provenancing studies tend to proceed by systematic elimination of probable sources but there is always the possibility that unidentified sources of raw material may have a similar geochemical signature. Fortunately, as talc has many industrial and commercial uses, there have been extensive studies on the talc deposits of Shetland. Within the Shetland archipelago, there are twenty three known sources of steatite. Of these at least seven have evidence of quarrying in prehistoric through to medieval times. In the first investigation, carried out at Bradford University (Clelland, Batt and Stern), geological samples were taken from four of Shetland’s steatite outcrops: Fethaland, Houbie, Cunningsburgh and Clibberswick. These were found to have easily measurable and distinctive magnetic properties, arising predominantly from soft magnetic minerals. Analysis of rare earth elements (REE), support the hypothesis that REE patterns are representative of individual sites. However, attempts to model the chemical processes undergone during the formation of each outcrop were unable to discriminate between the outcrops which suggests that each outcrop underwent the same formation process. The second investigation, undertaken at East Kilbride and Athens, had similar aims: twelve steatite outcrops on Shetland, including the four studied at Bradford, were characterised for their REE and other trace element contents, as well as their mineralogical and strontium isotope compositions.

Physics of the Earth and Planetary Interiors, 2012

ABSTRACT A chronological framework is an integral part of any archaeological interpretation but i... more ABSTRACT A chronological framework is an integral part of any archaeological interpretation but it is often restricted by the lack of precision in the dates available to the archaeologist. This is a particular problem in the Iron Age, due to the limitations of radiocarbon dating in this period; specifically the period between 700-400BC where the radiocarbon calibration curve provides large errors. Archaeomagnetic dating is predominately a method of dating materials that have been heated in antiquity. Therefore archaeomagnetic studies offer an underexploited opportunity to provide dates for the Iron Age through the study of past geomagnetic field, as recorded by archaeological materials. As with radiocarbon, archaeomagnetic dating requires a calibration curve to provide calendar dates. However, in order to produce a calibration curve it is necessary to assign a calendar date to every magnetic direction used to construct it. One of the main problems with the current method of calibrating magnetic directions is the imprecision of the calendar dates attributed to the magnetic direction determinations used in it. This ongoing research is attempting to improve on the independent dating associated with each data point in the current calibration curve. Unlike radiocarbon dating, there is evidence that the direction of the geomagnetic field was undergoing rapid changes between 700-100BC, so archaeomagnetism should be capable of high resolution dating during this period. This paper describes how evidence from the Iron Age hillfort at Rainsborough is being used to improve the current archaeomagnetic calibration curve for the UK.

Archaeomagnetic dating is a derivative dating method, matching regionally specific patterns of se... more Archaeomagnetic dating is a derivative dating method, matching regionally specific patterns of secular changes in geomagnetism, therefore needs a calibration curve. The calibration curve is a record of the secular variation in the geomagnetic field so is referred to as a secular variation curve (SVC). The current SVC for the UK is the accumulation of 60 years of research by geophysists (Aitken & Weaver 1962; Aitken & Hawley 1967; Clark et al. 1988; Batt 1997; Zananiri et al. 2007) and currently the section of the curve that relates to the first millennium BC is described by just under 100 magnetic directions. The pattern of change for each magnetic phenomenon has to be established by other chronometric methods, typically: historical records, radiocarbon or dendrochronology, as the secular variation pattern of geomagnetism is not predictable (Batt 1997). It is therefore necessary to assign a date to every magnetic direction used to construct the SVC. The main problem with the current...

This paper will present the results of an extensive re-evaluation and supplementing of the availa... more This paper will present the results of an extensive re-evaluation and supplementing of the available British archaeomagnetic records for the period between 2000 and 3000 years ago. The aim of this PhD research was to use archaeological and geological material to characterise changes in the geomagnetic direction in the UK. This period of time was selected for two reasons: firstly it represents the end of prehistory on this archipelago, the British Iron Age and therefore represents a period of significant archaeological interest; secondly, results from previous work on lacustrine records and other fired materials suggest that during this period the geomagnetic field over Western Europe experienced a rapid change in direction. The archaeological period currently suffers from poor chronological resolution. This is due to a combination of factors but mainly results from high degree of regional variation in the archaeology of the British Iron Age, which means that dating based on cultural...

Archaeometry, 2014

In rehydroxylation (RHX) dating, the activation energy of the rehydroxylation reaction is require... more In rehydroxylation (RHX) dating, the activation energy of the rehydroxylation reaction is required first in the estimate of a material's effective lifetime temperature (ELT), and second to correct the RHX rate constant obtained at a given measurement temperature to that at the ELT. Measurement of the activation energy is thus integral to the RHX methodology. In this paper, we report a temperature-step method for the measurement of activation energy and develop fully the underlying theoretical basis. In contrast to obtaining the activation energy from a series of separate experiments (each of which requires the sample to be dehydroxylated prior to measuring the RHX rate constant), the temperature-step method not only requires a single dehydroxylation at 500°C but also eliminates repeated acquisition of Stage I data, which are not required for dating purposes. Since the first temperature step is set to correspond to the temperature at which a dating determination is carried out, the measurement of rate constants at higher temperatures simply becomes an extension of dating. Consequently, the logistics of obtaining the activation energy of rehydroxylation are greatly simplified.

Journal of Archaeological Science

Archaeomagnetic dating offers a valuable chronological tool for archaeological investigations, pa... more Archaeomagnetic dating offers a valuable chronological tool for archaeological investigations, particularly for dating fired material. The method depends on the establishment of a dated record of secular variation of the Earth's magnetic field and this paper presents new and updated archaeomagnetic directional data from the UK and geomagnetic secular variation curves arising from them. The data are taken from publications from the 1950's to the present day; 422 dated entries derived from existing archaeo and geomagnetic databases are re-evaluated and 487 new directions added, resulting in 909 entries with corresponding dates, the largest collection of dated archaeomagnetic directions from a single country. An approach to improving the largest source of uncertainty, the independent dating, is proposed and applied to the British Iron Age, resulting in 145 directions from currently available databases being updated with revised ages and/or uncertainties, and a large scale reassessment of age assignments prior to inclusion into the Magnetic Moments of the Past and GEOMAGIA50 databases. From the significantly improved dataset a new archaeomagnetic dating curve for the UK is derived through the development of a temporally continuous geomagnetic field model, and is compared with previous UK archaeomagnetic dating curves and global field models. The new model, ARCH-UK.1 allows model predictions for any location in the UK with associated uncertainties. It is shown to improve precision and accuracy in archaeomagnetic dating, and to provide new insight into past geomagnetic field changes.

The authors report a preliminary study of the light stable isotopic (dD, d 13 C and d 18 O) value... more The authors report a preliminary study of the light stable isotopic (dD, d 13 C and d 18 O) values for bulk archaeological birch bark tars, over a geographical (e.g. Greece to Norway) and chronological (9500-3000 BP) range. For d 13 C an increase in fractionation with increase in latitude is observed in samples from Greece which are less depleted than those from northern Europe. There is no clear difference between the samples from northern Europe. There is no apparent trend in d 13 C value with the 14 C age of the sample. Due to biosynthetic fractionation all the samples are significantly depleted in 2 H and enriched in 18 O relative to the global meteoric water line. This study indicates that archaeological birch bark tar from Greece can be distinguished from those of northern Europe; this separation is probably based on the extreme geographical range of the samples examined here. But this does provide evidence that the birch bark tars were probably made locally rather than traded.

Archaeometry

To obtain accurate results in the RHX dating of ceramics, it is essential that the RHX measuremen... more To obtain accurate results in the RHX dating of ceramics, it is essential that the RHX measurements are continued until the rate of mass gain is constant with (time)1/4. In this paper, we discuss how the initial stages of mass gain are affected by the specific surface area (SSA) of the ceramic material. The paper provides guidance on experimental protocols to avoid dating results being distorted by relatively early-time mass gain data.

Physics of the Earth and Planetary Interiors, 2012

Archaeometry, 2013

Applied Geochemistry, 2006

Physics of the Earth and Planetary Interiors, 2012

Archaeometry, 2014

Journal of Archaeological Science

Archaeometry

To obtain accurate results in the RHX dating of ceramics, it is essential that the RHX measuremen... more To obtain accurate results in the RHX dating of ceramics, it is essential that the RHX measurements are continued until the rate of mass gain is constant with (time)1/4. In this paper, we discuss how the initial stages of mass gain are affected by the specific surface area (SSA) of the ceramic material. The paper provides guidance on experimental protocols to avoid dating results being distorted by relatively early-time mass gain data.

This paper will present the results of an extensive re-evaluation and supplementing of the availa... more This paper will present the results of an extensive re-evaluation and supplementing of the available British archaeomagnetic records for the period between 2000 and 3000 years ago. The aim of this PhD research was to use archaeological and geological material to characterise changes in the geomagnetic direction in the UK. This period of time was selected for two reasons: firstly it represents the end of prehistory on this archipelago, the British Iron Age and therefore represents a period of significant archaeological interest; secondly, results from previous work on lacustrine records and other fired materials suggest that during this period the geomagnetic field over Western Europe experienced a rapid change in direction. The period currently suffers from poor chronological resolution. This is due to a combination of factors but mainly results from high degree of regional variation in the archaeology of the British Iron Age, which means that dating based on cultural indicators (artefacts, building style etc) produces a spectrum of possible age ranges. This situation is further compounded by limitations with radiocarbon dating for this time period due to a plateau in the radiocarbon calibration curve. Therefore this period provides a promising target for improving the temporal resolution of palaeosecular variation curves and addressing a significant archaeological issue.

This research on palaeosecular variation has two unique aspects: the refinement of the chronological precision of secular variation records from archaeological material and investigations into the potential for combining directional data from geo-archives with archaeological material. Primarily the focus has been on improving the precision of the chronological assignment associated with each magnetic directional measurement from archaeological materials. A total of 114 magnetic directions related to the period 2000 to 3000 years ago have been re-evaluated. This resulted in an improvement in 89% of cases due to the critical application of archaeological dating evidence within a Bayesian framework. Furthermore, 105 new data points have been added, doubling the amount of data for this time period. Together these approaches have resulted in a more evenly distributed dataset over the time span of interest. Secondly the deposition of British lake sediments was re-assessed using Bayesian modelling procedures to improve the age estimates for these data. This was followed up with the development of a statistical approach to quantify the differences between directional data recovered from sedimentary and baked clay archives with a view to combining them. This methodology, developed to refine the British archaeomagnetic dataset, has improved the precision of the British SV curve and could be applied to other SV curves to provide a detailed snapshot of secular variation in periods of archaeological interest. The potential benefits of this research impact the related fields of modelling and interpretation of the global geomagnetic field.

Hillforts have been the focus of British Iron Age studies since the beginnings of field archaeolo... more Hillforts have been the focus of British Iron Age studies since the beginnings of field archaeology due to their conspicuous presence in the present day landscape. It has been noted that that there were different methods of constructing the key characteristic of hillforts, namely the presence of a circuit (or part) of artificial enclosing works. This prompted both the process of classifying these groups and attempts to trace the origin of these methods of construction. One of these subgroups is timber-laced ramparts and examples have been found all over Britain. However, in northern Britain over sixty timber-laced ramparts exhibit signs of vitrification; a feature that appears to be unique to this area of Britain but has also been observed on the continent, particularly the Atlantic fringes. Seven British vitrified hillfort sites have been sampled for archaeomagnetic dating and previous research has highlighted huge discrepancies in the dating of what appear to be a morphologically similar class of sites. This paper will present a re-evaluation of the dating evidence provided by earlier workers and will use these seven sites as a case study to introduce an updated version of the British archaeomagnetic calibration curve.

The British Iron Age marks the end of prehistory and was a period of change, yet in the archaeolo... more The British Iron Age marks the end of prehistory and was a period of change, yet in the archaeological record is unclear whether this was a time of upheaval and migration or prosperity and trade. Archaeologists want to answer these questions and comment on the rate and causes of changes but these discussions are limited by poor chronological resolution. Archaeomagnetism is an under-exploited dating technique with particular relevance to Iron Age archaeology due to the increase in pyrotechnological applications during this period for example: metalworking , ceramic production, salt manufacture, corn drying and enamelling. There is some evidence to suggest that investigations into the behaviour of the geomagnetic field during the first millennium BC may provide a promising avenue for research both for archaeomagnetic and radiocarbon dating. Therefore the overall aim of this research is to improve our ability to date the archaeological record in the first millennium BC in Britain using archaeomagnetic dating. This is achieved by focusing on improving the precision of the data used to construct the British archaeomagnetic reference curve, increasing the number of suitable data points and will include comparison with European datasets. This presentation will provide a summary description of the work undertaken on geological and archaeological datasets over the past 2 years, describe the methodologies devised to address this research question and outline the preliminary results.

Radiocarbon dating is problematic for the British Iron Age, not only due to the issues with the c... more Radiocarbon dating is problematic for the British Iron Age, not only due to the issues with the calibration curve during the first millennium BC but also in relating the organic material sampled to the archaeological events of interest. A critical assessment of how material culture is applied to the question of dating through typological sequences reveals that it is still rooted in essentially an evolutionary approach, although tempered by the stratigraphic relationships of the “type site”. It is argued here that the chronological framework underlying all Iron Age archaeological understanding is perhaps based on an outmoded concept. As humans utilise material culture to constantly redefine themselves and reinforce differences this creates problems in using typological sequences and cultural packages to date archaeology even over relatively small regions. Therefore some of the issues with dating this period are related to how archaeologists have been attempting to order the observed cultural changes. When in fact these patterns could be due to the nature of how large groups of people interact. To be able to objectively examine change and identify the forces that generated it, it is imperative to have an independent measure of time. Here archaeomagnetic dating provides a currently underexploited opportunity. This presentation will discuss the application and potential impact of this method of dating for the British Iron Age.

The primary aim of this research is to use studies of the geomagnetic field, as recorded by arc... more The primary aim of this research is to use studies of the geomagnetic field, as recorded by archaeological materials, to identify and characterise decadal timescale changes in the Earth’s magnetic field. This research will redefine the direction of the geomagnetic field between 800BC and AD100, improving the precision of archaeomagnetic dating and therefore the chronology of this period. This work will benefit archaeomagnetic dating, which can directly date the last use of architecture associated with pyrotechnology, for example hearths, ovens and furnaces.

An initial survey of data within the current archaeomagnetic direction calibration dataset suggests that the associated median date for just over 100 data points fall within the period 800BC-AD100 but these previous studies need re-evaluation. This project will also involve collecting new data from this period and investigating the potential to incorporate magnetic data from sedimentary sequences, given the different mechanisms of detrital and thermo remenant magnetisation recording. Furthermore, the relationship between the geomagnetic field and the radiocarbon calibration curve in this period will be examined, possibly contributing to the debate on palaeoclimate.

The establishment of a reliable chronology is a fundamental aspect of archaeological investigatio... more The establishment of a reliable chronology is a fundamental aspect of archaeological investigation. The traditional view of the Viking dispora across the North Atlantic has been developed from details recorded in historical documents centuries after the events they are describing. Atlantic Vikings are believed to have left their Scandinavian homelands around 800AD; migrating across the Atlantic Ocean they settled in each of the archipelagos along this route and reached America around 1000AD. Advances in scientific methods of dating archaeological assemblages have provided a corpus of evidence which is independent to the conventional art-historical and literary based approach currently employed. The aim of this project was to compare the scientific dating evidence to dates provided by the literary evidence. This was achieved by collating and critically assessing the dating evidence provided by chronometric methods relating to the Viking landnám event across the island groups in the North Atlantic. This survey provides evidence to suggest that there was some Nordic presence in Atlantic Scotland before the traditional date of 800AD but with regards to the other island groups it did not reveal evidence that refuted the currently established time-frame for expansion.

Archaeomagnetism is an area of research that utilises the magnetic properties of archaeological m... more Archaeomagnetism is an area of research that utilises the magnetic properties of archaeological materials to date past human activity. This research aimed to use the evidence of past geomagnetism, as recorded by archaeological and geological materials, to identify and characterise short timescale changes in the Earth’s magnetic field. This contribution to the discipline focused on the first millennium BC, as there is evidence that during this time the Earth’s magnetic field experienced rapid changes in direction. This work focused on an established weakness in archaeomagnetic studies, i.e. the application of archaeological information to assign a date range to the magnetic directions. The date ranges for 232 magnetic directions from 98 Iron Age sites were reviewed and a programme of fieldwork produced 25 new magnetic directions from 11 Iron Age sites across Britain. The approach developed in this thesis has made significant improvements to the data examined, which represent the prehistoric section of the British secular variation curve (SVC). These data have been incorporated into the British archaeomagnetic dataset that now comprises over 1000 magnetic directions and will be used to generate future British SVCs. The potential of the near continuous records of geomagnetic secular variation from British lake sediment sequences to SVCs was explored. This showed that these sediments have recorded the relative changes in the Earth’s magnetic field but the dating and method of constructing the British master curve requires revision. As SVCs are predominately used as calibration curves for archaeomagnetic dating, this work provides a foundation for a revised and extended British SVC. This revision would be to the mutual benefit of studies in archaeology and archaeomagnetism, as the latter could potentially enable high-resolution dating of Iron Age material, providing a viable alternative to radiocarbon dating.

"The establishment of a reliable chronology is a fundamental aspect of archaeological investigati... more "The establishment of a reliable chronology is a fundamental aspect of archaeological investigation. The traditional view of the Viking dispora across the North Atlantic has been developed from details recorded in historical documents centuries after the events they are describing. These documents suggest that Atlantic left their Scandinavian homelands around 800AD; migrating across the Atlantic Ocean they settled in each of the archipelagos along this route and reached America around 1000AD. Advances in scientific methods of dating archaeological assemblages have provided a corpus of evidence, which is independent to the conventional art-historical and literary based approach currently employed.

The aim of this project was to compare the scientific dating evidence to dates provided by the literary evidence. This was achieved by collating and assessing the dating evidence provided by chronometric methods, relating to the Viking landnám event across the island groups in the North Atlantic. A total of 660 dates from over 180 Viking sites were collated from across the region. The methodology devised in this study to identify reliable dates meant that only 121 dates from 29 sites were selected for inclusion in this survey. The results provide some evidence to suggest that there was some Nordic presence in Atlantic Scotland before the traditional date of 800AD but with regards to the other island groups it did not reveal evidence that refuted the currently established time-frame for expansion. This work has revealed the limitations in the present approach to dating this episode of human history and puts forward some suggestions for future development.
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This study describes an investigation into the feasibility of using magnetic analytical methods a... more This study describes an investigation into the feasibility of using magnetic analytical methods and trace element analysis to characterise archaeologically recovered steatite from the site of Old Scatness, Shetland. The magnetic methods employed were magnetic susceptibility, magnetic viscosity and the intensity of natural remanence magnetisation and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was utilised to obtain rare earth element compositional data, all these techniques are rapid and minimally destructive.

In order to compare the archaeological results to reference geological data, a series of experiments were performed to examine the potential effects of anthropogenic activity and diagenesis on the chemical and magnetic composition of steatite. The models employed in this study suggest that neither the domestic use of steatite nor the burial environment have any detrimental effects on the ability to characterise it. By comparing selected archaeological artefacts from Old Scatness’ steatite assemblage to geological reference material it can be suggested that there was a shift in the location that was exploited for steatite procurement over time. The conclusions are restricted by the limited reference collection but an attempt has been made to integrate archaeological contextual information with the analytical data.

In summary it is possible to obtain composition data from archaeological steatite with minimal damage and thus could provide direct evidence for contact between societies in North Atlantic region.

website: http://datingceramic.manchester.ac.uk/index.htm Following removal from the kiln, fired c... more website: http://datingceramic.manchester.ac.uk/index.htm Following removal from the kiln, fired clay ceramic begins to chemically combine with atmospheric moisture (rehydroxylation). This results in a super-slow, progressive increase in mass which occurs in two distinct stages. The RHX rate constant is defined as the gradient of the linear second-stage mass versus (time) 1/4 graph and is unique to any particular material . Following reheating at 500 O C in the laboratory, which removes all the chemically combined water (dehydroxylation), the material once again gains mass according to the (time) 1/4 law and this occurs at the same rate as in the freshly fired material . This is the basis of RHX dating ): the mass of water removed at 500 O C is measured; from the RHX rate constant the time that it would take to recombine with that mass of water is calculated and this is equivalent to the age of the sample. We were aware of the effect of temperature, as RHX is a chemical reaction, but when we started to work with archaeological fired clay material getting consistent and usable data became very challenging.

The overall aim of this research is to improve our ability to date the archaeological record that... more The overall aim of this research is to improve our ability to date the archaeological record that relates to the first millennium BC in Britain using archaeomagnetic dating. This will achieved by focusing on improving the precision of the data used to construct the British archaeomagnetic reference curve and increasing the number of suitable data points. The ability to produce a high resolution secular variation record of the geomagnetic field is restricted by the nature of the source of information available. For the late Holocene epoch, around 5000BP in the UK, the most frequently used are: remains of past anthropogenic activity and evidence from natural sediments deposited during the interglacial period. The mechanisms by which these two difference sources record the contemporary geomagnetic field differ and this has led to some difficulties in combining them into a single record. By focusing on the first millennium BC, which is characterised by a rapid change in declination, this research is attempting to quantitatively assess the "time lag" between the geomagnetic field recorded by sedimentary and archaeological material from the UK. It has been possible to improve the precision and accuracy of the chronological placements designated to the archaeological magnetic directions in the current British SVC. This poster presents the progress made in the first year and a proposed methodology for combining these data with magnetic directions from UK lake sediments.

This research commenced in October 2007. The primary aim is to use studies of the geomagnetic fie... more This research commenced in October 2007. The primary aim is to use studies of the geomagnetic field, as recorded by archaeological and geological materials, to identify and characterise short (decadal) timescale changes in the Earth's magnetic field.

Recent excavations at Mine Howe have focused on a large circular stone built structure, 5m in dia... more Recent excavations at Mine Howe have focused on a large circular stone built structure, 5m in diameter with a single entrance on the southern wall and numerous alcoves . It appears to have been deliberately constructed as a smithy due to the amount of evidence for metalworking . Two phases of use have been identified and during the earliest phase, 7.2, a central flag based hearth with an upright stone backstop was on the southern side. A small clay lined hearth was set into the floor to the east of the hearth with a flue leading into the base. It is thought that this was used to heat and melt copper alloy due to the large amount of small crucibles and snippets of copper that were recovered from the vicinity. Archaeomagnetic dates from the second phase of activity, Phase 7.3, put the last use of the central hearth to 100BC to 100AD (Outram & Batt 2004).

Archaeological interpretation requires a chronological framework but it is often overlooked how d... more Archaeological interpretation requires a chronological framework but it is often overlooked how dependent absolute dating is on a few key sources and diagnostic artefact types.