Radiocarbon dating: Some practical considerations for the archaeologist

The article is divided into four main sections in each of which a key aspect of radio-carbon dating is discussed with emphasis on the practical implications for users of dates. The four topics which the article attempts to deal with are, in turn, (i) the effect on the radiocarbon timescale of the variations in atmospheric ¹⁴C now known to have occurred in the past and the role of other absorlute dating methods in investigating these, (ii) laboratory measurement of ¹⁴C, (iii) selection of optimum samples for dating and (iv) some of the limitations of the final dates. The theme is essentially that the technical difficulties of radiocarbon measurement in the laboratory have been overcome to the extent that the physical measurements can now be made with high precision, that is to within ±1% or better, as a routine. Thus, it is more important than ever (a) that only reliable samples having very firm associations should be dated and (b) that pretreatment of such samples by the dating laboratory to remove any age contaminants should be completely effective. However, in addition to the recognized statistical limitations, the absolute accuracy of radio-carbon dating is limited by the past ¹⁴C variations. Coupled with the requirements of proper association and pretreatment of samples is the long-term need to establish an overall correlation between radiocarbon and calendar years. At present this is still a matter for final agreement by the laboratories concerned. Meanwhile, when all possible steps have been taken to ensure the reliability of the date messurements, these can strictly only be compared with one another in terms of radiocarbon years bp. In practice this is often too restrictive but any attempts at calibration must be regarded as approximations for the time being. In this article the lower and upper case notation advocated in Antiquity46, 265, for radiocarbon and calendar years respectively has been followed.     

ESTIMATION OF THE AGE OF A PRE‐INDUSTRIAL IRON SITE IN KOREA*

A pre‐industrial iron‐smelting site in Korea, whose period of active use is placed on typological grounds between the eighth and 18th centuries ad , has been dated using accelerator mass spectrometry and thermoluminescence. The ages of two charcoal samples were 77 ± 25 and 81 ± 25 years bp , with the calibrated date for both ranging from ad 1700 to ad 1955, while a clay fragment dated to ad 1650 ± 50. The results from typology and radiocarbon seem insignificant due to the considerable uncertainties involved, but in combination with the thermoluminescence result they place the most probable date of the site at around ad 1700.     

RADIOCARBON DATES FOR BEESWAX FIGURES IN THE PREHISTORIC ROCK ART OF NORTHERN AUSTRALIA

Accelerator mass spectrometry radiocarbon ages have been taken for a test suite of small samples of material removed from some of the ‘beeswax’art figures found in rock shelters in northern Australia. The results indicate that we can reliably date this unique form of rock art with no noticeable damage. We had not expected to find figures of any great antiquity, and so we were surprised to find that the ages obtained spanned the time period from the recent past to about 4000 BP.     

A NEW DATE FOR THE NEANDERTHALS FROM EL SIDRÓN CAVE (ASTURIAS,NORTHERN SPAIN)*

Torres et al. (2010 ) published a series of radiocarbon, AAR, ESR and OSL dates from the site of El Sidrón, northern Spain, which is notable for the discovery of the partial remains of 12 Neanderthals. Whilst the non‐radiocarbon methods suggested an age beyond 32 600–46 300 years, direct radiocarbon dates on the human fossils were inconsistent, ranging between 10 000 and 50 000 bp . This study uses the ultrafiltration pre‐treatment protocol to obtain a date of 48 400 ± 3200 bp (OxA‐21 776) on a bone fragment and confirm the antiquity of the Neanderthal assemblage. Moreover, it demonstrates the comparability of the ultrafiltration and ninhydrin bone radiocarbon pre‐treatment protocols, and highlights the need for appropriate screening methods where valuable collections with poor biomolecular preservation are sampled for collagen extraction.     

ESR Dating of Micoquian Industry and Neanderthal Remains at K?lna Cave, Czech Republic

Electron spin resonance (ESR) and mass spectrometric U-series dating has been carried out on teeth recovered from K?lna cave during the excavations of 1961–76. Linear and early uptake (LU and EU) age estimates are similar due to low internal U content of the teeth. In general, ESR ages decrease upward in the section, but teeth from stone-rich (“lumpy”) layers give anomalously young ages, due to uneven dose-rate distribution. Elephant molars also give anomalously low ages, apparently due to self-absorption of gamma dose. Disregarding anomalous data, earliest appearance of Micoquian lithics and last occurrence ofDicerorhinus kirchbergensisin layer 9b is dated to 69±8 ka, which places them near the oxygen isotope stage (OIS) 5a/4 boundary. Neanderthal remains and the latest occurrence of Micoquian lithics in level 7a are dated to 50±5 ka, in good agreement with an uncalibrated radiocarbon date for this level of about 45 ka. The interstadial character of the fauna of this level also agrees with its date which places it in OIS 3. We also report that three stadial/interstadial cycles recognized in the lithological, faunal and palynological record of levels 9b through 7a at Kölna occurred during the timespan from about 70 to 50 ka.     

Methods for the Study of Ancient Hair: Radiocarbon Dates and Gene Sequences from Individual Hairs

Genetic data from archaeological specimens provides a potent new approach for addressing questions in prehistory. Hair from archaeological sites is an important but overlooked data source amenable to molecular analysis. To date DNA identification from hair is limited to modern samples. Our study is the first to report DNA recovery from a 9800-year-old specimen. We report methods used to extract mitochondrial DNA and obtain accelerator mass spectrometry radiocarbon dates (AMS-¹⁴C) from hairs plucked from a piece of ancient bighorn sheep (Ovis canadensis nelsoni) skin found at Smith Creek Cave, Nevada. The ability to obtain reliable radiocarbon dates and DNA sequences from single ancient hairs opens new possibilities for addressing biological questions in prehistory.     

A possible case of treponemal disease from England dating to the 11th–12th century AD

This short report describes a human skeleton from an archaeological site in England showing signs of treponemal disease. A radiocarbon determination indicates that it is firmly pre‐Columbian in date. The implications for recent debates concerning the origin of treponemal disease in Europe are discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

Radiocarbon dating of prehistoric hearths in alpine northern Sweden: problems and possibilities

The chronology of prehistoric Sami settlement sites has previously been established by conventional radiocarbon dating of bulk charcoal samples associated with hearths from sunken hut floors (stállo-foundations). Here we present results of a comprehensive dating exercise of stállo-foundations in the alpine area of northern Scandinavia using Accelerator Mass Spectrometry (AMS) radiocarbon dating of charcoal. Over a 3 km² study area, AMS calibrated ages of hearth charcoal from 22 stállo-foundations across 12 sites securely date these features to between cal. AD 640 and AD 1180. Only small variations in age were found between charcoal samples from different areas of a given hearth. Statistical analysis of all the charcoal AMS radiocarbon dates obtained reveals that 12 stállo-foundations across nine sites are contemporaneous and date to the Viking Period (AD 800–AD 1050). The tightly constrained AMS-based chronology of stállo-foundations contrasts with the existing chronology based on conventional radiocarbon analysis, which places these features within a significantly greater time-frame of between AD 600 and AD 1900, with most dates ranging between AD 800 and AD 1350.This discrepancy is likely to result from the necessity of collecting composite hearth charcoal particles, which may originate from different phases of occupation, in order to achieve the required final carbon content for conventional radiocarbon analysis. We argue that the new AMS-based radiocarbon chronology of stállo-foundations presented here supersedes the existing chronology based on conventional (Gas Proportional counting) radiocarbon analysis and we advocate the use of AMS radiocarbon dating in future hearth investigations.     

A first prehistoric case of tuberculosis from Britain

A likely case of tuberculosis in an Iron Age human burial from Dorset, England is described. Osteological examination and biomolecular study support the diagnosis. A radiocarbon determination indicates a date range for the burial of BC 400–230. This case represents the earliest reported case of tuberculosis from Britain, and indicates that the disease was present here prior to the Roman invasion. Copyright © 2003 John Wiley & Sons, Ltd.     

A further consideration of neolithic dogs with special reference to a skeleton from Grime's Graves (Norfolk), England

The complete skull and skeleton of a dog were recently excavated from the neolithic flint mines at Grime's Graves in Norfolk. As very few complete skeletons of dogs have been found from neolithic contexts in Britain a detailed metrical comparison was made between the Grime's Graves specimen and dog skeletons of comparable antiquity and completeness from Easton Down and Windmill Hill in Wiltshire.Implicit in the study of the dog from Grime's Graves was the need to date it precisely. As the skeleton could not be sacrificed for radiocarbon dating, closely associated antlers of Red deer (Cervus elaphus) were used for this purpose. The date of the Grime's Graves dog is compared with the dates for other dog remains from recently excavated neolithic sites in the British Isles.     

ABSOLUTE DATING OF THE AEGEAN LATE BRONZE AGE

A recent argument for raising the absolute date of the beginning of the Aegean Late Bronze (LB) Age to about 1700 B.C. is critically examined. It is argued here that: (1) the alabaster lid from Knossos did have the strati-graphical context assigned to it by Evans, in all probability Middle Minoan IIIA, c. 1650 B.C.; (2) the attempt to date the alabastron found in an early Eighteenth Dynasty context at Aniba to Late Minoan IIIA:1 is open to objections; (3) radiocarbon dates from Aegean LB I contexts are too wide in their calibrated ranges and too inconsistent both within and between site sets to offer any reliable grounds at present for raising Aegean LB I absolute chronology to 1700 B.C. Other evidence, however, suggests this period began about 1600 B.C., i.e. some fifty years earlier than the conventional date of 1550 B.C.     

Chronostratigraphy of an Eroding Complex Atlantic Round House,Baile Sear,Scotland

A high-resolution chronostratigraphy has been established for an eroding Atlantic round house at Sloc Sàbhaidh (North Uist, Scotland), combining detailed OSL profiling and dating of sediments encompassing the main bracketing events associated with the monument, radiocarbon AMS dates on bone recovered from excavated features and fills within it, and TL dates on pottery and burnt clay. Concordant OSL and radiocarbon evidence place construction of the wheelhouse in the first to second centuries AD, contemporary with dates from the primary occupation. Beneath the wheelhouse, clay deposits containing burnt material, attest to cultural activity in vicinity to the monument in the preceding second to first centuries BC. At a later date, the southern wall collapsed, was rebuilt, and the interior spaces to the monument re-structured. The chronology for the later horizons identified from the sediment luminescence dates extends to the second half of the first millennium AD, which goes beyond the range of the radiocarbon dates obtained. The data from ceramics encompass both periods. The juxtaposition of the dating evidence is discussed relative to short and longer chronologies for this Iron Age monument. Corollaries of this research are the implications that based on the long chronology, some of the ecofacts (bone) appear to be residual, and that the temporal duration of Hebridean Coarse Ware may extend into the second half of the first millennium AD.     

The age of the Dalton culture: a Bayesian analysis of the radiocarbon data

ABSTRACT

Since a radiocarbon chronology of the Dalton culture in the Southeast was first proposed, several new sites have been dated. I propose a new chronology based on radiocarbon dates from sites in the Dalton Heartland and its eastern periphery using Bayesian statistical models in OxCal and an analysis of the associated diagnostic projectile points. The analyses indicate that the Dalton culture probably evolved from the Clovis or Gainey phenomena about 12,680?cal?BP (ca. 10,700?BP) and lasted at least until ca. 10,400?cal?BP (ca. 9,200?BP), if not several centuries later. I propose early and late Dalton phases that follow changes in how Dalton points were made and resharpened. It appears that the people living to the east of the Heartland followed a different trajectory of projectile point evolution. There, notched points appear about 11,500?cal?BP, while in the Heartland, true notched points do not appear in large numbers until the Graham Cave point over 2,000 years later. The chronologies demonstrate that early, coeval, region-wide cultural changes may not have been the norm. They also raise interesting questions about how people in the Heartland and its eastern periphery interacted.     

RADIOCARBON DATING ARCHAEOLOGICAL SAMPLES IN THE EASTERN MEDITERRANEAN, 1730 TO 1480 BC: FURTHER EXPLORING THE ATMOSPHERIC RADIOCARBON CALIBRATION RECORD AND THE ARCHAEOLOGICAL IMPLICATIONS*

The East Mediterranean Radiocarbon (Inter‐)Comparison Project (EMRCP) has measured time series of radiocarbon ages for known age samples of German oak (GeO) and for samples from the near‐absolutely placed Gordion juniper dendrochronology from central Anatolia. In this paper, we review the data for the calendar years from 1730 to 1480 bc , relevant in particular to controversy and debate concerning the absolute date of the Minoan eruption of the Santorini (Thera) volcano. We consider the issue of the radiocarbon (¹⁴C) dating of the Santorini eruption, and the problem of how this relates to the archaeological record and historical chronology of Egypt in light of the ¹⁴C data. We find that these ¹⁴C data, and other recent radiocarbon work, provide good grounds to be confident in the possibility of a robust radiocarbon‐based chronology for the eastern Mediterranean. In contrast, as the radiocarbon case becomes stronger, questions must be asked about some archaeological dating: in particular, at the site of Tell el‐Dab‘a in the Nile Delta of Egypt.     

Problems in the interpretation of radiocarbon dates: the Pastoral Neolithic of East Africa

For the Pastoral Neolithic of East Africa radiocarbon dates suggest two apparent anomalies in the archaeological record: pastoralism in the Central Rift at perhaps 7000 bp, and the very long duration of particular pottery traditions. This paper examines the dating evidence closely, in particular the assertion that apatite gives more reliable dates than collagen. Both the assertion and the anomalies appear to be false. It is shown that there is no firm evidence for pastoralism in East Africa before about 4000 bp. Similarly, the Narosura tradition is of shorter duration and more recent than previously supposed. The meagre dating evidence for the Namoratunga sites and its implications are also assessed. Examination of the dates for the Pastoral Iron Age shows that the Turkwel tradition is dated only by a single date and that the appearance of twisted cord rouletted pottery in the present millennium post-dates the end of stone tool manufacture by several centuries. The paper concludes with a plea for more critical assessment of radiocarbon dates and for greater rigour in their presentation.     

DIRECT GAMMA-RAY SPECTROMETRIC DATING OF FOSSIL BONES: PRELIMINARY RESULTS

A non-destructive gamma-ray spectrometry was used for direct dating of fossil animal and human bones taken from an alluvial Quaternary site in northern Italy. The ages were obtained using the U-Pa method: the chronological results are in agreement with palaeofaunal indicators and taphonomic data. The ages of two samples showed concordance with the U-Th method; in a third case good agreement was also found with the radiocarbon date, thus lending credence to our modified gamma spectrometric method.     

A NEW DIRECT RADIOCARBON AMS DATE FOR AN UPPER PALAEOLITHIC HUMAN BONE FROM SIBERIA

A new AMS radiocarbon date has been obtained from a Siberian human bone sample taken directly from a cranial fragment. The specimen comes from the north‐east Siberian site of Pokrovka 2 (55⁰19′46.30″N, 92⁰26′48.80″E). The remains consist of the anterior portion of the cranium or the superior part of the face; that is, the forehead and the roof of the eye sockets. Sadly, indifferent features of the frontal bone do not allow a confident diagnosis of the sex of the individual. The evidence suggests, however, that the remains are probably those of a young adult (teenager) and an anatomically modern human, rather than a Neanderthal. Radiocarbon dating was undertaken at the Oxford Radiocarbon Accelerator Unit (ORAU). The radiocarbon age determination of the bone fragment, 27 740 ± 150 bp (OxA‐19850), is one of the earliest direct dates for a modern human from Siberia. The Pokrovka cranial fragment dates to the middle Upper Palaeolithic of Eurasia and is broadly contemporary with the human remains from the famous eastern European site of Sunghir. When the radiocarbon age is compared with the Cariaco Basin ¹⁴C data set and the Greenland oxygen isotope record of NGRIP, it corresponds with Greenland Interstadial 5, a warmer phase of the Last Glacial period, although this is a preliminary conclusion, and is based on climate records that may or may not be wholly synchronous between the two locations.     

Special Studies: The Pre-Chavín Stone Sculpture of Casma and Pacopampa

Abstract

In a recent article, “Early Carving From Pampa de las Llamas-Moxeke, Casma Valley, Peru,” Thomas Pozorski and Shelia Pozorski (Journal of Field Archaeology 15 [1988] 114–119) describe an important stone sculpture discovered in their 1987 excavations of Huaca A at Pampa de las Llamas-Moxeke, Casma Valley, Peru. They argued that it was the oldest securely-dated sculpture in Peru based on a radiocarbon date of 1565 b.c. (unrecalibrated), and deemed it unique on the basis of comparisons with the corpus of early stone sculptures from Peru. The dual purpose of this short contribution is to: 1) suggest that on the basis of radiocarbon measurements available it cannot be demonstrated that the Huaca A sculpture is older than the hundreds of stone sculptures from Cerro Sechin in Casma; and 2) draw attention to some intriguing similarities between the Huaca A sculpture and a stone carving from Pacopampa in the Chotano Valley of the Peruvian highlands. These two points highlight the inadequacy of our understanding of the origins of stone sculpture in Peru.     

THERMOLUMINESCENCE DATING OF A CRUCIBLE FRAGMENT FROM AN EARLY TIN PROCESSING SITE IN TURKEY

Archaeological exploration in the Taurus mountains at Göltepe in south-central Turkey has uncovered a site indicating the presence of extensive tin ore mining and smelling operations The most recent find of smelting crucible fragments allowed for a thermoluminescence-hased age determination spanning a late fifth to early third millennium BC date. This result is consistent with a number of radiocarbon dates derived for charcoal also found at the site. The importance of this site relates to the possible tin production and subsequent trade with southwestern Asia which would have provided this otherwise scarce ingredient to bronze technology in that area. This date is directly for crucible material and thus confirms the antiquity of tin smelting at Göltepe.