Chris Burbidge - Academia.edu (original) (raw)

Papers by Chris Burbidge

This study supports a new investigation into the construction, occupation and utilisation history... more This study supports a new investigation into the construction, occupation and utilisation history of a Mediaeval ring fort near Newry, southwest Northern Ireland (section 2). Optically stimulated luminescence (OSL) profiling and age determinations have been made for two sequences of sediments accumulated in the ring ditch surrounding the fort, and potential has been assessed for TL dating of a Souterrain-Ware sherd from a pit feature within the site complex (section 3). The archaeological significance of the age determinations has been reviewed in the light of the luminescence results and the samples’ depositional contexts, to constrain the deposition/formation dates of the sampled sediments (section 6). A total of 31 profiling (sections 5.1, 5.2) and 12 age (section 5.5) determinations were made. Profiling measurements were made using simplified equivalent dose determination procedures on polymineral coarse and hydrofluoric etched sand-sized mineral grains (sections 4.2.2). Dose ra...

This study supports a new investigation into the timing and rates of clay formation in mid-Arabia... more This study supports a new investigation into the timing and rates of clay formation in mid-Arabia as a function of climatic and geomorphological context. Optically stimulated luminescence (OSL) age determinations have been made for a range of dune, wadi, sabkha and playa deposits across mid-Arabia (section 3). The geomorphological significance of the age determinations has been reviewed in the light of the luminescence results and the samples’ depositional contexts, to constrain the deposition/formation dates of the sampled sediments (section 6). 36 sets of dose rate determinations were made (sections 4.2.1, 5.1) using thick source beta counting, high resolution gamma spectrometry, measured water contents and calculated cosmic dose rates, including separate measurements on bulk and sieved (<1 mm) material from one inhomogeneous sample. 39 sets of equivalent dose determinations were made (sections 4.2.2, 5.2) using the OSL signals from sand sized grains of quartz separated from each sample, including a travel dosimeter, two modern surface samples, and one repeat. A total of 35 age determinations were made (section 5.3), including two each from the middle and bottom parts of two vertically cored samples. Dose rates ranged from 0.42 to 2.4 mGy/a, and with the exceptions of the travel dosimeter and one sample with its OSL signal in saturation, De values ranged from 0.01 to 24 Gy. Age estimates for these samples ranged from 0.01 to 15 ka, the average being 5 ka ± 5 (section 5.3). Uncertainties on the age estimates were commonly 10 – 20 % at one standard deviation, though percentage uncertainty was higher for age estimates close to zero. Overall the data indicated that a variety of geomorphological features have ages spread through the late glacial period and early-mid Holocene (~15 to ~4 ka). Few features date to between ~4 ka and ~0.2 ka, but many date to within the last ~200 years (section 6.3). Most of the youngest features were active dune slipfaces and thin sand sheets, they also included a thicker structureless sand, relict foresets, and playa deposits, but no sabkha. The older features were mainly aggraded sabkha deposits (horizontal bedding), relict foresets (including those in which sabkha has formed), and thick structureless sands. Of these older features, the foresets and sands all dated to before ~7 ka. This period includes both wetter and dryer climatic phases, but is notable for dramatic sea level rise in the Arabian Gulf. The coastal aggraded sabkhas, and one inland sabkha, have ages ranging from 3.3 ka ± 0.5 to 5.9 ka ± 1. These correspond to a period of fluctuating wet and dry climatic conditions, and sea level fluctuating about its present day level. The results indicate major sand emplacement in the study region during late glacial and early Holocene sea level rise (16 – 7 ka), followed by mid-Holocene (6 – 3.5 ka) sabkha formation as sea levels stabilised. A lack of samples dating from the late Holocene, followed by a number dating to the last ~ 2 centuries, indicates that either there was a hiatus in landform formation until relatively recent times, or that features formed since the mid Holocene have been reworked, possibly on a bicentennial timescale.

Ditch and pit fills from four archaeological sites in the Baixo Alentejo region of Portugal were ... more Ditch and pit fills from four archaeological sites in the Baixo Alentejo region of Portugal were studied to explore the relationship between Luminescence Profiling (IRSL, OSL, TSL, sensitivity and sensitization) and X-ray diffraction (XRD) analyses. Series of small (ca. 10 g) samples were collected, through the different fill materials. XRD results show that the predominant mineral is calcite (40-90%), and this exhibited the strongest relationships with luminescence behaviour. In the present sites it was often related to high absorbed doses, and so to residual signals rather than low dose rates. Commonly, the calcite content and the absorbed dose value tended to increase from the top to the bottom of a section. Layers with lower calcite content and residual luminescence signals were used to stratigraphically define different phases of accumulation. The best reset luminescence signals for dating at these sites come from the layers with the lowest calcite content. In other cases similar absorbed doses through archaeological stratigraphies, independent of composition, were interpreted to indicate that signals in the different mineral fractions were well reset prior to accumulation in the structure.

This is the second report relating to the Anuradhapura Hinterland project. It includes details fr... more This is the second report relating to the Anuradhapura Hinterland project. It includes details from the first report (Burbidge and Sanderson, 2007: 13 samples dated from 6 sites) and OSL age estimates for a further 13 samples from 4 sites sampled in 2007, following review of sampling strategy in the light of results from the 2006 field season.

Journal of Coastal Research, 2013

A large earthquake shook the offshore region of Portugal in November 1 st 1755 with an estimated ... more A large earthquake shook the offshore region of Portugal in November 1 st 1755 with an estimated magnitude of 8.5±0.3 in the Richter scale. It lead to the massive destruction of the city of Lisbon, which was followed by intense fires. Although most of the detailed consequences of the earthquake and tsunami focused in Lisbon, the effect of tsunami destruction was also reported in other locations along the Peninsula coasts and Morocco. At Setúbal, located 30 km to the south of Lisbon in the Sado estuary, evidences of inundation were also documented, reporting wave heights that reached a first floor height. Despite the magnitude of the inundation in the interior of the estuary, there has not been reported any evidence of the impact of this event on the estuarine shorelines. In order to understand the consequences of such a wave on the sandy shores of the region, we explore the inlet shoreline and seaward exposed region of the estuary, the Tróia peninsula. To do so, we integrate multiple types of data and information: dune ridge position were extracted from aerial photographs, shorelines from the historical maps, shoreline progradation rates, Ground Penetrating Radar profiles and optically stimulated dating of barrier sediments. This information allows us to reconstruct the shoreline following the tsunami, documenting a greater impact towards the inlet where the water flow concentrate as it entered the estuary. The impact of the tsunami in Tróia peninsula translates on the erosion of about 1000 years of barrier deposits within the spit end.

Radiation Measurements, 2011

This study explores the potential for using photon-stimulated luminescence of quartz grains to re... more This study explores the potential for using photon-stimulated luminescence of quartz grains to retrospectively evaluate multi-kGy gamma radiation doses. Subsamples from two ceramic tiles were given 60 Co gamma doses of 1, 3, 5, 15 and 30 kGy (nominal), accompanied by PMMA dosimeters and quartz grains from a geological sample known to exhibit thermally-transferred optically-stimulated luminescence (TTOSL). Following gamma irradiation, quartz grains were prepared from each subsample. OSL and TTOSL signals were measured for different preheat temperatures, and following re-irradiation with beta doses designed to equal the nominal gamma doses. OSL responses to 10 Gy beta test doses were measured following each cycle of high dose irradiation. Gamma doses were predicted from the beta responses, to evaluate the effectiveness of retrospective dose evaluation for different signal integrals, preheat combinations, and dose intervals. The use of linear modulation limited maximum OSL signal levels to 1.5 Â 10 6 cps without reducing detector sensitivity, for the measurement of smaller TTOSL signals. The dosimetric behaviour of the three samples differed significantly: the best results were obtained from the pre-prepared geological quartz. OSL signals evident at short stimulation times, which are conventionally used for dosimetry and dating, did not in general appear appropriate for dosimetry in the range of doses examined. They exhibited dose response characteristics that were highly preheat dependant and variable in form between samples, which contained rapidly saturating and/or non-monotonic components. Higher preheats, up to 300 C, preferentially removed OSL and TTOSL signals evident at longer stimulation times: those that remained yielded growth in signal with dose to approximately 10 kGy, but the accuracy of retrospective dose determinations was variable. TTOSL signals evident at short stimulation times increased proportionally with dose when 300 C preheats were used, up to 30 kGy of beta irradiation for two of the samples, but the given gamma doses were underestimated by 15e23%. Refinement of the present measurement protocol may improve assessment of the gamma doses, and the short term stability of the signal needs to be characterised, but the observed level of accuracy is already sufficient to provide approximate estimates for severity of radiation exposure. The present study has identified certain elements of OSL and TTOSL signals that can be used, in combination with a relatively severe preheating regime, to retrospectively evaluate doses of tens of kGy: beyond the range traditionally possible using quartz.

Quaternary Geochronology, 2007

A luminescence-based approach to the rapid characterisation of sites in terms of their datability... more A luminescence-based approach to the rapid characterisation of sites in terms of their datability and sedimentary history is described (luminescence profiling), and contrasting results presented for three Palaeolithic archaeological sites in Russia. Three mineral/grain-size fractions (polymineral silt-sized, polymineral sand-sized, quartz-enriched sand-sized) were separated from each of many small samples taken through the sites' stratigraphies. Luminescence signals from the different fractions were measured using infra-red light, blue light, and thermal stimulation. Patterns in luminescence sensitivity and equivalent dose values are used to indicate which sites, samples, fractions and/or signals may yield meaningful luminescence ages, and the experimental effort that may be required to obtain said ages. Case studies range from a site where a detailed chronostratigraphy might be produced using a limited number of full luminescence dates to tie in the profiling results, to a site where profiling indicates there is little chance of producing useful luminescence dates. These interpretations are based on dialogue between the luminescence profiling results and archaeological, palaeoenvironmental, and geomorphological evidence. Luminescence profiling is shown to be a useful tool for understanding sedimentological process at each site, independent of full luminescence dating.

Journal of Archaeological Science, 2012

Neutron tomography (NT) has been applied to visualize the inner structure of ancient Portuguese g... more Neutron tomography (NT) has been applied to visualize the inner structure of ancient Portuguese glazed tiles undergoing conservation treatments. Neutrons have the advantage of interacting strongly with hydrogen, so NT is able to map hydrogenous compounds with high sensitivity. The present study explores its potential for assessing the distribution of the consolidant Paraloid B-72 inside tiles, to evaluate the efficiency of two different methods of treatment: brushing and immersion in solution. Using a prototype NT setup at the Reactor Português de Investigação (Sacavém, Portugal), each two-dimensional image is obtained from a 90 s exposure, at a thermal neutron flux of 2 Â 10 5 n cm À2 s À1 at the irradiation site. The neutron beam has a diameter of 5 cm, so fragments with outer dimensions up to 4.8 cm can be inspected. Samples are automatically rotated by an angle of 0.9 between successive images. Images were obtained before and after the application of the consolidant. The results obtained show that: (i) NT is a useful tool for visualization of the inner structure of ancient glazed tiles, and to assess penetration depth of consolidant and its distribution inside the tile; and (ii) brushing with 10% Paraloid Ò B-72 in acetone solution appears to be more efficient than immersion. Neutron tomography showed a greater and more uniform retention of resin inside the tile if the brush is used to apply the consolidant, to increase the cohesion of the object.

AIP Conference …, 2004

The optically stimulated luminescence from minerals is proving to be a very useful dating techniq... more The optically stimulated luminescence from minerals is proving to be a very useful dating technique in archaeology and physical geography. In this work we study the analysis of the relevant data from a Bayesian viewpoint, comparing some simple age and noise models. FIGURE 1. (a)-(c) Data obtained by irradiating quartz grains with a laboratory beta-dose of 5, 10 and 20 Gy respectively; (d) the amalgamated measurements for the 103 (= 43 +25 +35) grains.

Single crystal chips of Al2O3 : C (TLD500) were evaluated and employed for measurements of combin... more Single crystal chips of Al2O3 : C (TLD500) were evaluated and employed for measurements of combined gamma, beta, and cosmic dose-rate. A regenerative dose optically stimulated luminescence (OSL) measurement procedure is described, using the closed source of a RisH reader for irradiation. The reproducibility of these measurements was assessed for both irradiation within the reader, and during ÿeld deployment. Combined dose-rate measurements using the chips were corrected for beta attenuation by comparison with independent dose-rate measurements. Dosimeters were buried for up to 3 weeks in the ÿeld, providing parallel measurements of in situ combined dose-rate for 79 OSL samples.

Archaeometry, 2001

A series of deposits from the agricultural in®eld of the multiperiod settlement mound, Old Scatne... more A series of deposits from the agricultural in®eld of the multiperiod settlement mound, Old Scatness, were investigated for their potential to yield optically stimulated luminescence dates. Luminescence properties of quartz grains were found to vary through the sequence, but dates were successfully obtained from ®ve deposits, including anthropogenic soils, windblown sands and sands within midden deposits. Single-aliquot equivalent dose measurement was found to be the most appropriate method for dating the deposits. The OSL dates obtained accorded well with the dates provided by archaeological evidence and included the postmedieval, Iron Age, Bronze Age and Neolithic periods of Shetland, while a substantial midden was dated to the Bronze/Iron Age transition.

It has recently been shown that it is possible to construct standardised curves of the sensitivit... more It has recently been shown that it is possible to construct standardised curves of the sensitivity corrected growth in optically stimulated luminescence (OSL) with exposure to ionising radiation, and that they may be used in the dating of quartz and polymineral samples. Standardised growth curves are particularly advantageous where measurement time is limited, as once they have been defined, only the natural signal and the response to a subsequent test dose are required in order to determine the equivalent dose of a sub-sample. The present study is concerned with the application of the standardised growth curve approach to OSL dating of Holocene age samples. Systematic changes in the shape of the standardised growth curve of coarse-grain quartz are identified as the size of the test dose is varied, because of non-proportionality between the test dose and the luminescence test response. The effect is characterised by fitting the change in gradient of the standardised growth curve as test dose is varied. An equation is defined to describe standardised growth as a function of regenerative dose and test dose.Regenerative dose responses of other samples in this study are treated as unknowns and recovered through different growth curves to compare precision and accuracy of various methods of De determination. The standardised growth curve is found to yield similar precision to conventional fits of single aliquot regenerative data, but slightly poorer accuracy. The standardised growth curve approach was refined by incorporating the measurement of one regenerative response for each aliquot as well as its natural signal. Measurements of this additional data point for aliquots of 22 samples were used to adjust the standardised growth equation, improving its accuracy. The incorporation of this additional data point also indicated a systematic uncertainty of 2.4% in the estimates of De.

Annali dell’Università di Ferrara Museologia Scientifica e Naturalistica, 2010

Different analytical methods comprising mineralogical and chemical analysis and thermoluminescenc... more Different analytical methods comprising mineralogical and chemical analysis and thermoluminescence dating were used to assess the most appropriate techniques for the characterisation and dating of a ceramic collection. This study demonstrates the complementary nature of these techniques. The materials studied consist of ceramics from the collection of the Estrada Foundation, which will form part of a future museum in Abrantes Portugal.

Journal of Archaeological Science, 2010

Bulk samples of mortars from the Santa Eulalia de Bóveda temple (NW Spain) have been characterize... more Bulk samples of mortars from the Santa Eulalia de Bóveda temple (NW Spain) have been characterized from a chemical and mineralogical point of view, with the aims of contributing technological and provenance inferences, and evaluating possible correlations with the various identified stages along historical periods of construction.Mortar samples were analyzed by X-ray diffraction and neutron activation analysis.Mineralogical associations found are

Journal of Archaeological Science, Feb 1, 2013

We identify and offer new explanations of change in water management infrastructure in the semi-a... more We identify and offer new explanations of change in water management infrastructure in the semi-arid urban hinterland of Anuradhapura, Sri Lanka between ca. 400 BC and AD 1800. Field stratigraphies and micromorphological analyses demonstrate that a complex water storage infrastructure was super-imposed over time on intermittently occupied and cultivated naturally wetter areas, with some attempts in drier locations. Our chronological framework, based on optically stimulated luminescence (OSL) measurement, indicates that this infrastructure commenced sometime between 400 and 200 BC, continued after Anuradhapura reached its maximum extent, and largely went into disuse between AD 1100 and 1200. While the water management infrastructure was eventually abandoned, it was succeeded by small-scale subsistence cultivation as the primary activity on the landscape. Our ﬁndings have broader resonance with current debates on the timing of introduced ‘cultural packages’ together with their social ...