Radiocarbon Dates from the Oxford Ams System: Archaeometry Datelist 31

This thirty-first list of AMS determinations measured at the Oxford Radiocarbon Accelerator Unit (ORAU) is predominantly made up of those measured since the start of 1996. However, it also includes some determinations measured earlier which have not been published in previous lists. The dates presented here include those measured through the NERC-funded Oxford Radiocarbon Dating Service (ORADS), those funded by English Heritage and Historic Scotland, and those submitted to the laboratory on a commercial basis. All dates have been measured using the procedures outlined in Law and Hedges (1989), Hedges et al. (1989; 1992) and Bronk Ramsey et al. (Arch. List 30). AMS determinations with OxA numbers greater than 6293 were measured either as graphite (if sufficiently large) or as CO2 (Bronk Ramsey and Hedges 1997). In accordance with international radiocarbon convention all dates are expressed in radiocarbon years before AD 1950 (years BP) using the half-life of 5568 years. Errors are quoted as one standard deviation (1 σ) and are based on an assessment of all the contributions to the error in the laboratory isotope ratio measurement. Natural fractionation of carbon isotopes is accounted for by measuring the δ13C values relative to PDB (with errors of approximately 0.3‰). All combining procedures and significance tests are based on Ward and Wilson (1978). Comments composed by the Laboratory on the basis of information supplied by submitters are given without attribution. All calendrical dates quoted, unless stated otherwise, have been calibrated using the OxCal computer program (Bronk Ramsey 1995; 1998a; 1998b; 2001) using atmospheric data from 'INTCAL98' (Stuiver and van der Plicht 1998), and are quoted to 95.4% probability. Previous Archaeometry datelists are referred to in the form: Arch. List 30. Details of methods used are described fully in our in-house documentation. This is regularly updated and archived, so the exact method used for any sample is always fully recorded. Over the 7–8 years the measurements in this list cover, much work has been done to ensure the reliability and reproducibility of measurements made at the laboratory. To a large extent this is to do with good laboratory practice and standardisation of all aspects of the dating process, from calibration of equipment to full traceability of key components and reagents used during the dating process. These aspects of 'Quality Management' are often best assessed by those outside the laboratory and, to this end, the lab was accredited to the ISO-9002 standard by the BSI in January of 2000. On a more scientific level, one important test of a radiocarbon dating laboratory is its ability to determine the correct radiocarbon concentration in material whose true age is known. This means the regular measurement of international standards, known-age material and background material (very old material of different types used to estimate sample treatment blanks) and participation in International Radiocarbon Intercomparisons. Another and equally important test is the ability to reproduce measurements on real archaeological material, since this is usually in a poorer state of preservation than known-age material. Here we summarise the results relating to measurements of known-age material (generally tree rings supplied to us by the Queen's University of Belfast, with known ages taken from the INTCAL98 calibration curve) and duplicate measurements made on unknown samples. The results for about 750 measurements on known-age material shown in Table 1 show that error terms quoted on the radiocarbon determinations do reflect very well the true uncertainty. The number falling within one, two and three standard error terms (σ) is very close to the expected proportion (see cf. values in the table header). They also show that any laboratory offset relative to the calibration curve is well under ten years. Overall, the figures suggest a reliability of about 99% (since the average proportion lying within 3σ is 98.93% rather than the theoretical 99.74%). Here we define reliability to be a measure of the probability that a typical sample will give a result in accordance with the quoted error. No process is totally reliable, however, and this can be seen in the details of the data in Table 1. There was one significantly aberrant (well over 2σ) measurement in 1997 and another in 1999. However in 2000 there were nine such measurements. Three of these were due to a known batch-specific problem (the results from these batches were not released). Measurements from batches involving the remaining six (about 4% of the total number) were also rejected, but were unexplained at the time. This intermittent problem with graphitisation was eventually diagnosed and eliminated in November 2000. Having already repeated approximately 150 measurements, we estimated that a further 2–3% of the output from 2000 (20–30 determinations) could have been affected. A further set of repeated measurements on samples especially likely to have been affected identified 21 determinations liable to be in error, which have now been withdrawn (see Appendix I). We therefore estimate, from the data on known-age material, that 99% of measurements for this year should now lie within the expected distribution, as for other years (though see next section). The results for about 250 measurements made in duplicate on unknown samples are shown in Table 2. These show, as one would expect, that duplication on real archaeological samples is harder to achieve than on selected, well-preserved material. These measurements include both randomly duplicated samples (now performed on ∼5% of submitted samples) as well as requested duplicates (either by submitter or laboratory, e.g. because of technical difficulty). Such duplicated samples can be expected to contain a higher proportion of 'problem samples', but are a fair reflection of the actual dating process. (For example, not all samples can be said to be 'single entities'.) Taking these data as they are, we can conclude that the reliability of the dating process, which is about 99% for well preserved standard material, is reduced to about 97% for real samples. It is likely that the distribution is not accurately Gaussian and it would be unwise to compensate for this decrease in reliability by increasing the estimated error (by, in this case, around 10%). In any case, the results vary from year to year, and indeed the latest results are now very close to the theoretical limit. Also, the number of samples rejected from this analysis has gradually fallen over the years in question, reflecting the more careful selection of sample material by submitters in collaboration with the laboratory. Quality control of the dating process is essential if radiocarbon results are to be used as the basis for assessing archaeological chronologies. The known-age and duplicate data presented here support the determinations published in this datelist. These data show that the error terms quoted on the measurements can be relied upon to provide a realistic assessment of the true uncertainty in the radiocarbon determinations. They also demonstrate that there is no significant laboratory bias relative to the radiocarbon dates used to build the radiocarbon calibration curve (INTCAL98) and so the measurements published here should be directly comparable to those produced in other laboratories with similar quality control. Obviously much work lies behind the dates published in this list. We must first thank the submitters for their care in sample selection, collaboration during the dating process and for providing comments on the dates for this publication. We would also like to acknowledge all the hard work of past and present members of ORAU who have done so much of the work involved in the dating process and who are not in the author list for this paper: Diane Baker, Angela Bowles, John Foreman, Gillian Hanford, Greg Hodgins, Rupert Housley, Martin Humm, Phil Leach, Neil Murphy, Tamsin O'Connell, Vanessa Pashley, Paul Pettitt, Angie Stokes, Christine Tompkins and G.-J. van Klinken. We also acknowledge that little of this work would ever have been attempted without the generous funding of NERC Scientific Services, English Heritage and Historic Scotland. Fragment of a human right clavicle (catalogue number GS 267), identified by Andrew Chamberlain in 1994 at the British Geological Survey, Keyworth. This previously unidentified bone was among a collection of faunal remains retrieved in 1822 from the third bone cave at Oreston Breakwater Quarry, Plymouth, Devon (NGR SX 502538), submitted by A. T. Chamberlain, Dept. Archaeol. & Prehistory, Univ. Sheffield, through the NERC-funded ORADS facility. Comment (A. T. C): fauna from the cave include a mixture of Pleistocene and Holocene species (Whidbey and Clift 1823; Chamberlain and Ray 1994). The Early Mesolithic date for GS 267 is similar to direct dates on human remains from other coastal caves in southern Britain including Kent's Cavern, Devon (OxA-1786: 8070 ± 90 BP), Worm's Head Cave, Gower (OxA-4024: 8800 ± 80 BP) and Ogof-yr-Ychen, Caldey Island (OxA-7690: 8290 ± 55 BP; OxA-7691: 8210 ± 55BP; OxA-7741: 8415 ± 65 BP). However the specimen from Oreston Breakwater Quarry may have been treated with Isinglass (a collagen-based preservative) and this radiocarbon determination must therefore be regarded as a minimum estimate of the age of the specimen, as the possible inclusion of modern collagen would bias the determination towards a younger date. Sample from skull from the site of Skirethorns (NGR SD 965645), North Yorks, submitted by S. Kirrane, District Museums Officer, Craven Museum, Skipton, N. Yorks. Comment (S. K.): this skull came to us as a result of superficial survey work at the Skirethorns site undertaken by the Department of Archaeological Sciences at Bradford University in 1994. The site forms part of an interesting plateau which has provided finds from the Mesolithic to the Medieval period. On this particular site there is evidence of what appears to be a Viking farmstead, and also of Iron Age round huts. The skull was retrieved from a deep crevice in the limestone, at the rear of one of the huts. Its date confirms Iron Age occupation. The fact that it was discovered without any other human bones has raised interesting questions about ritual Celtic 'head cults', however opinions are divided on this point. The fact that the skull was dated to this period added to its interest and it became the focal point for a major exhibition here at the Craven Museum (1997). This contrasted the archaeological interpretation of the site and the skull, with that of a local artist. This exhibition stimulated a great deal of interest and in this small, local way has contributed to public understanding and support for archaeology. Sample of bone from Taywood Homes, Fulbourn (NGR TL 552257), Cambridgeshire, submitted by C. Duhig, 109 Sturton Street, Cambridge, CB1 2QG. Comment (C. D.): this sample was submitted for the Cambridgeshire Constabulary, being a skeleton of suspiciously-modern appearance, found in a context which had no evidence of antiquity and in a location which might suggest that the bones were of forensic interest. They were extremely pleased to have the antiquity of the remains demonstrated. A sample of bone from Shavards Farm, Meonstoke, Hampshire (NGR 61651065), submitted by N. Stoodley, 207 Farley Lane, Braishfield, Romsey, Hampshire, SO51 0QL. Comment (N. S.): during work on the early Anglo-Saxon cemetery and settlement at Shavards Farm in 1998 and 1999 it was discovered that excavations on the site in the 1980s by Mike Hughes had recovered a crouched inhumation burial. It was suspected that the burial took place in the Bronze Age and a sample of bone was sent for dating in order to confirm this. However, the Middle Iron Age result was not expected and is further evidence, along with an enclosure, for activity at this time. Samples of bone from Southampton High Street (NGR SU 41991108), Hampshire. Submitted by A. D. Russell, Archaeology Unit, Heritage Services, Civic Centre, Southampton. Comment (A. D. R.): OxA-5941 and −5942 were from human remains found within the medieval town of Southampton at the lower end of the High Street. OxA-5941 was from remains found in C. Platt's excavation of 1966. Three partial skeletons were found, one cut by the construction of a twelfth to thirteenth century stone house, but they had no independent dating evidence. Further work on the adjacent site in the 1990s produced a human molar from a late Saxon deposit. This raised the possibility that an earlier cemetery had occupied the site before the late Saxon town was founded c. 950 AD. The two dates would appear to provide proof of this, and raise interesting questions about the sites relationship with Hamwic (AD 650–850), situated less than I km to the northeast. The settlement that the cemetery served has yet to be located. Sample of bone from St. Mary's Churchyard (NGR SU 42651159), Southampton, submitted by A. D. Russell, Archaeology Unit, Heritage Services, Civic Centre, Southampton. Comment (A. D. R.): OxA-7187 was obtained from bones of a human foot encountered during repairs to the nineteenth century churchyard wall of St Mary's Church, St Mary Street, Southampton. Although long considered to be the mother church of middle Saxon Hamwic (AD 650–850) there is little real evidence to back up this assumption. This new date fits well with dates from two skeletons found under the nearby pavement a few years ago (OxA-5447 and −5448). These all go to show that bodies were being buried some distance from the church by the ninth century. Sample of bone fromYsgol Twm O'r Nant, Denbigh, (NGR SJ 05956662) Wales, submitted via the Univ. Bradford, Dept. Archaeol. Sci., by C. Roberts, Dept. Archaeol., Univ. Durham, through the NERC-funded ORADS facility. Comment (C. R.): the site was dated archaeologically to pre-Columbus and therefore, with a skeleton with bone changes suggestive of venereal syphilis, we wanted to see whether it was actually pre-Columbian in date. It seems that the dates provided indicate that it may be but may not be. Of course, dates such as these are important for the discussions of the evolution and development of syphilis in the Old and New Worlds. A sample of bone from Hyde Abbey, Winchester, England (NGR SU 48323013), submitted by H. Rees, Historic Resource Centre, 75 Hyde Street, Winchester, SO23 7DW. Comment (H. R.): although it was a possibility that the date would be before the Norman Conquest, we were not surprised that it was later, as the disarticulated fragment could have been redeposited from any time in the late Saxon or medieval periods. It was quite surprising, however, that the calibrated ranges were in the seventeenth and eighteenth centuries (1520–1570, 5.4%; 1630–1690, 41.1%; 1730–1810, 40.1%; 1920–1950, 8.8%), as the site should have ceased to be used for human burial at the Dissolution in 1538. The date range AD 1520–1570 therefore fits the archaeological and documentary evidence best. Three samples of human bone and a fourth of olive wood from Cerro Virtud de las Herrerias, Cuevas de Almanzora, Almeria (37:17N 47:00W), Spain, submitted by R. W. Chapman, Dept. Archaeol., Univ. Reading, through the NERC-funded ORADS facility. Comment (R. W. C): three samples of human bone and a fourth of olive wood charcoal (with some bark attached) were taken from a Middle Neolithic collective burial in a pit, excavated in 1994: OxA-6713 dates a female aged 35–50 years, OxA-6714 an adult 35–45 years and OxA-6580 a juvenile, probably male, aged 14–15 years. The dates form an internally consistent series, dating to the early-mid fifth millenniumcal BC. Taken overall, the samples for Cerro Virtud provide the first reliably contextualised absolute dates for the Neolithic in lowland south-east Spain, extending its duration to a possible fifteen hundred years. Cerro Virtud is the first example of non-megalithic, Neolithic collective burial to be excavated in this region, although there are parallels in other parts of southern Spain (Montero Ruíz et al. 1999). The site has also yielded evidence for copper metallurgy at a similarly early date (Ruíz Taboada and Montero Ruíz 1999). Sample of bone from Gatas, Turre, Almeria (37:07N 01:53W), Spain, submitted by R. W. Chapman, Dept. Archaeol., Univ. Reading, through the NERC-funded ORADS facility. Comment (R. W. C): the sample dates the ribs of a juvenile, probably male, aged 14–16 years, and buried in a sealed stone cist, tomb 39, in a stratified context in the Bronze Age settlement of Gatas. According to the stratigraphy and to multiply-dated samples from other burials at (see Arch. and et al. tomb dates to of the c. BC. Dating was to confirm this and to show the late of stone as burial the expected period of time for tomb In the of laboratory error, this that either there is a or that the of the the construction and of the stone Samples of bone from de Spain, submitted by R. W. Chapman, Dept. Archaeol., Univ. Reading, through the NERC-funded ORADS facility. Comment (R. W. C): the samples date a de in a in a stratified context in the Bronze Age of the settlement of a aged years was on the and with a copper and by an adult male, aged 35–45 years, with the and The was with and and There are no of or Dating of both burials was to confirm the of and the the The dates suggest the took place within years of with the female the in other of such burials in south-east Spain these dates suggest the practice of by but at two or more from Samples of bone from Spain, submitted by R. W. Chapman, Dept. Archaeol., Univ. Reading, through the NERC-funded ORADS facility. Comment (R. W. C): the samples date a burial in a in a stratified context in the Bronze Age of a aged years, with a copper was by a of the age and the stone was sealed with no evidence of or Dating of both burials was to confirm the of and the de (see the dates confirm the order of is the female and is the and the practice of burials of different Spain, submitted by R. W. Chapman, Dept. Archaeol., Univ. Reading, Reading, through the NERC-funded ORADS facility. Comment (R. W. C): these two dates are in full with previous dates and confirm the interpretation of the ritual in the c. and (see et al. 1999). dates one of the first in the which has been preserved as a skeleton in a context of burial and bone On the other dates a burial in the of collective of the Samples from Spain, submitted by R. W. Chapman, Dept. Archaeol., Univ. Reading, through the NERC-funded ORADS facility. Comment (R. W. C): the is an burial cave in a deep in the of It was discovered by in and excavated in et al. 1999). the disarticulated of and human bones were found the long of and a sealed with a of and including wood and with cut human AMS dating was undertaken to the range for of bone and in different of the cave and are samples of from the the of the samples date human bone in 1. Taken the dates show that the cave was used as an from c. BC. The latest date for bone is from a sample on of the wall the to the cave bone samples from caves in the in the of submitted by R. C. and of Natural and N. Museums of and were undertaken with the support of the de The radiocarbon determinations presented here are divided three and Early Mesolithic Comment (N. R. and C. sites in are known to contain Early Mesolithic human of are collective used over a long period of time and to which the were The date of the of the confirms the of this of practice at the of the Holocene period. the of Mesolithic collective includes at ten in and the southern part of England in in southern with the of the and the Cave, the other known are from or excavations which give less about the exact of the these that collective burials in caves were during the ninth and in more the dates of human bones from the or the indicate the of this We a for these and this first with the date of the human bones from the the Mesolithic is by a great in The of the this The Middle Neolithic Comment (N. R. and C. these dates on human bones from caves show that the also had to the collective tomb as in the The is a good example 1994). The samples used for the other dates from old but the of a now suspected and that is and with the time of the excavation at the end of the nineteenth century. the quality of these it is now that the collective burial is not to the and a large part in the Middle Neolithic of the at the of the Middle Neolithic in southern and the 1999). The Neolithic Comment (N. R. and C. the dates presented here collective burials and to the and contain no They can be added to about dates already known for southern the nineteenth about collective have been discovered in the and some of burial from the The of the collective burials so dated to the first of the third and their place in a large including the of the and those from the in 1997). comments on the date from can be found in et al. These samples of human bone from collective burials discovered in the cave of and on the of the of They were excavated by in the and submitted by and of Natural Comment (R. C. and A. and that the skeletons to the period. This at first because of the burials found in the caves of the are dated to the However, a of the during the excavations of has been performed by A. and A. Museums of and It that to the Bronze and the Iron and another one to the of the first century AD. the site of has been to the on the basis of the and the fauna the of which support to the dates obtained here and to the possible of cave in during the period. Samples of human bone from submitted by Univ. Comment The of the burial an to the and the results confirm this attribution. Samples of bone from the site of submitted by Comments by and A. Comment (A. and in 1998 A. found in the a with two a bone point an as well as human bones and The can be to at three an adult with bones a and also with bones and and an adult with bone among part of a skull These finds were on a of to the of of and found there with It is that these finds were during in the modern of not from the the Samples from the bone point and a bone fragment to to the were sent for dating to the The bone fragment a date of ± 90 δ13C the bone point not contain collagen to date. This first age is now by the ORAU dating the adult and a fragment of the the sample of the skull a very date a fragment to an adult is of age the date for all samples. The new ORAU dates suggest that at three human were found at These are to burials of the period the and the so not by dated sites in the Samples in this were submitted by Street, and T. University in with R. T. and Samples of human bone from of late Pleistocene age submitted to ORAU include remains from archaeological (the burial at the in and human remains from the in which have been to the and material from in the and important of the dating program are human remains recovered from without an but to the late A number of are to the earlier of the and have contributed to the of the and development of modern In of the of this material, it to determine the reliability of results of dating and The fragment was discovered in with a number of faunal remains lying on the of the