Relation between radiocarbon,archaeological dating and sediment properties on the example of colluvial deposits (NE Poland)

This study focuses on the analysis of the structural and textural features of the colluvial (deluvial) deposits in the Suwałki Lake District (NE Poland) and their absolute age. The colluvium has a thickness of up to 150 cm. The dates of the peat under colluvium or lowermost fossil humus-rich horizons point to the ages from 5405±80 BP to 480 BP. Deposition of material at the footslope is a result of a denudation triggered by human action (surface water erosion and tillage erosion) and usually corresponds with the settlement stages. The ¹⁴C dating of deposited sediment sometimes indicated to older dates of colluvium then the archaeological evidence available for examined sites. Locally, the overlying fossil humic horizon was older then the lowermost one. The textural features of the colluvial deposits such as: the content of fine fraction, weak sorting and relationship between the mean grain-size (Mz) and the sorting index (σ₁) were used to recognize sediment redeposited from the upper part of the slope. Basing on the mineral composition and electrical conductivity of fossil humus horizon it is possible to say whether the soil was degraded or aggraded. These features of the humus-rich horizons occurring between colluvial sediments can be used to explain discrepancy between the radiocarbon dating and archaeological evidence.     

OPTICAL DATING RESULTS FOR BRITISH ARCHAEOLOGICAL SEDIMENTS

In this paper optical dating results for a range of British archaeological sediments are presented to illustrate the potential this method offers for archaeologists. The optical dating is shown to offer an absolute method for directly dating the deposition of sediments for an age range of approximately 1–300ka. Problems have been found with recuperation of the optically stimulated luminescence signal and insufficient bleaching at deposition of the sediment. A suitable correction method for the recuperation has been found and a method of identifying insufficient bleaching is suggested.     

DATING OF THE HOMINID (HOMO NEANDERTHALENSIS) REMAINS ACCUMULATION FROM EL SIDRÓN CAVE (PILOÑA,ASTURIAS, NORTH SPAIN): AN EXAMPLE OF A MULTI‐METHODOLOGICAL APPROACH TO THE DATING OF UPPER PLEISTOCENE SITES

The age of Neanderthal remains and associated sediments from El Sidrón cave has been obtained through different dating methods (¹⁴CAMS, U/TH, OSL, ESR and AAR) and samples (charcoal debris, bone, tooth dentine, stalagmitic flowstone, carbonate‐rich sediments, sedimentary quartz grains, tooth enamel and land snail shells). Detrital Th contamination rendered Th/U dating analyses of flowstone unreliable. Recent ¹⁴C contamination produced spurious age‐values from charcoal samples as well as from inadequately pretreated tooth samples. Most consistent ¹⁴C dates are grouped into two series: one between 35 and 40 ka and the other between 48 and 49 ka. Most ESR and AAR samples yielded concordant ages, ranging between 39 and 45 ka; OSL dating results permitted adequate bracketing of the sedimentary layer that contained the human remains. Our results emphasize the value of multi‐dating approaches for the establishment of reliable chronologies of human remains.     

THE CHRONOSTRATIGRAPHY AND GEOARCHAEOLOGICAL SIGNIFICANCE OF AN ALLUVIAL GEOARCHIVE: COMPARATIVE OSL AND AMS 14C DATING FROM GREECE*

The Basin of Phlious in southern Greece is known for its thick colluvial and alluvial deposits from the Holocene. It offers a good opportunity to reconstruct the history of Holocene soil erosion and its interaction with historical farming activities. In this study, we present new results based on optically stimulated luminescence (OSL) dating from the Basin of Phlious. The comparison between OSL and ¹⁴C AMS ages shows good agreement, and demonstrates the need for the detection of insufficiently bleached OSL samples in order to obtain accurate results. The discovery of a Neolithic site, buried under thick alluvial deposits, confirms the hitherto postulated Neolithic human impact on the landscape.     

On the frontier of the Western Shire,British Central Africa

Superficial deposits (residual, colluvial, alluvial) are important as environmental resources in tropical environments. An understanding of their formation through varying time periods is essential to a correct interpretation of their economic and hazard potentials. This requires an integration of process studies with a reconstruction of longer term development. Saprolite formation is considered over 10⁵‐10⁷ yr, while colluvial and alluvial sediments are commonly Late Quaternary (10³‐10⁵ yr) in age. The importance of Quaternary environmental changes in the humid tropics to an understanding of heavy mineral placer deposits in West Africa and Indonesia is illustrated. It is concluded that geomorphologists can often make their most important contributions to developing areas by offering a sound interpretation of landsurfaces and their underlying deposits for engineers, geologists and pedologists, with whom a close working relationship is essential.     

ANTHROPOGENIC IMPACT ON THE LANDSCAPE OF SOUTHERN BADENIA (GERMANY) DURING THE HOLOCENE—DOCUMENTED BY COLLUVIAL AND ALLUVIAL SEDIMENTS*

In the study area (the Upper Rhine Lowlands and the southern Black Forest), colluvial and alluvial sediments could be dated with the aid of ¹⁴C analysis, archaeological finds, pollen analysis and stratigraphic assessments. On the basis of these dated deposits, six different maps have been produced showing the distribution of the colluvial and alluvial sediments for the corresponding archaeological cultural periods. For each of these periods, the intensity of human impact on the environment has been estimated in relation to climatic conditions and different economic activities; for example, woodland clearance and mining activities.     

FIFTY YEARS OF LUMINESCENCE DATING*

Luminescence techniques for dating both heated materials (e.g., pottery and burnt stone) and sediments have gone through three phases in the past 50 years. The first 22 years, from 1957 to 1979, were devoted to thermoluminescence (TL) techniques applied to heated material. In the next six years, from 1979 to 1985, it was found that TL dating could be applied to sediments. However, the TL signals of both quartz and feldspar grains observed for modern sediments were small, but were not zero, thus making them useful only for older sediments. A new luminescence signal that was totally zeroed by exposure to sunlight for a relatively short period of time, a few hours or less, was found; this led to the development of optically stimulated luminescence (OSL) dating techniques in 1985. Further developments have continued to the present day. Within the past 22 years, 1999 was also a year with major developments. A reliable procedure for single aliquots of quartz that have a rapidly bleached (‘fast’) OSL component was formalized and an instrument that allowed rapid measurement of equivalent doses for single grains was constructed. These developments have led to OSL becoming a major dating tool in Quaternary geology, at least for the past 100 000 years, and in archaeology, particularly as related to the dispersal of modern humans.     

OPTICAL DATING OF ANTHROPOGENIC SEDIMENTS AT THE ARCHAEOLOGICAL SITE OF HERRENBRUNNENBUCKEL,BRETTEN-BAUERBACH (GERMANY)*

Optical dating was applied to natural and anthropogenic silts at an Iron Age settlement in southern Germany. The natural sediments were dated accurately and allowed study of the human impact on the landscape. The studied anthropogenic sediments were infills of cellars and ditches. Again, deposits derived from soil erosion proved to be datable using infrared-optically stimulated luminescence. However, optical dating of fine grained sediments was at its limits when sediments consisted of a mixture of bleached and unbleached grains. This is shown on sediments of known age originating from cellar infills. Improvements were obtained when using the 560 nm emission and a partial bleach approach. Experimental evidence shows that the D_E versus shine-time plot discloses insufficient bleaching only in cases in which all grains are insufficiently bleached to the same degree.     

HOLOCENE ACCUMULATION OF COLLUVIAL AND ALLUVIAL SEDIMENTS IN THE WEIßE ELSTER RIVER VALLEY IN SAXONY,GERMANY*

Geoarchaeological investigations at two archaeological excavation sites lead to new results with respect to the Holocene landscape development of an archaeologically important loess landscape of Central Europe. Colluvial and alluvial sediments were sampled during archaeological excavations on the valley edge of the Weiße Elster and dated by means of ¹⁴C, TL and dendrochronology, and on the basis of archaeological finds. Thus, for the first time, the development of a valley edge of a river in the Leipzig area, which has been continuously settled for 7300 years, can be reconstructed. The first soil erosion on the valley edge is established towards the end of the Atlantic period. During the High Middle Ages, a colluvial sediment developed. Its deposition time can be limited to between ad 1000 and 1100. The flood loam near Großstorkwitz, which can be stratified by means of the soil and colluvial deposits, originated in the late Sub‐Boreal and early Sub‐Atlantic, as well as after ad 1100. During the first millennium ad, a soil developed in the older flood loam, which indicates a phase of reduced flood loam sedimentation.     

On the Possible Origins of an Unusual (Mid to Late Holocene) Coastal Deposit,Old Punt Bay,South‐East Australia

An unusual coarse, shelly sedimentary unit is found elevated above present mean sea level in a sheltered pocket embayment at Old Punt Bay in south‐eastern Australia. The coarse sediments, diverse microfauna, and large shelly macrofauna of mixed affinity suggest that the deposit is the result of high‐energy deposition. The deposit was previously thought to have been deposited 1000–1300 cal bp based on one shell dated using ¹⁴C and amino acid racemisation. However, additional ¹⁴C dating indicates a likely age of ～2500 cal bp . Regardless of age constraints, the presence of rock‐encrusting oyster shells and large articulated bivalves, suggests that the depositional event must have been capable of removing and transporting coarse sediments (rock clasts), bivalves, and oysters shells from a variety of seaward environments and depositing them with little abrasion, something storm waves are unlikely to do. The deposit may be tsunamigenic. If a tsunami origin is accepted, the new dating results indicate that it is possibly coeval with a tsunami event previously reported to have affected several other sites along the coast of New South Wales at c. 2900 cal bp . Consequently, this deposit provides evidence for the event at a new site and importantly, a tighter constraint on the likely date of the events occurrence. It further adds weight to the developing catalogue of palaeotsunamis that may have affected the south‐eastern coast of Australia. Regardless of the deposit's origins, if viewed from a coastal planning perspective, this deposit indicates that this part of the coast has experienced large‐scale overwash events in the past that if repeated, would be catastrophic. There are serious implications for risk management.     

Fossil fruit identification by SEM investigations, a tool for palaeoenvironmental reconstruction of Dmanisi site, Georgia

Archaeological excavations and multidisciplinary studies at the site of Dmanisi (Lesser Caucasus, Georgia) have provided an assemblage of lithic artefacts and numerous palaeontological and human remains in a volcano-sedimentary context dating to the early Lower Pleistocene. The sieving of archaeological sediments from Dmanisi also yielded mineralised botanical macro-remains that were analysed according to a particular protocol. The use of scanning electron microscopy (SEM) allowed the comparison between fossil fruit remains and modern specimens, leading to a precise identification of the earlier. Seed remains recognised by this method belonging to several taxa from the Boraginaceae family as well as to the genus Celtis L., of the Ulmaceae family. The ecological requirements of these taxa suggest the presence of xeric conditions, a result that is in accordance with data obtained by faunal and stratigraphic studies.     

On the applicability of post-IR IRSL dating to Japanese loess

Recent work on infrared stimulated luminescence (IRSL) dating has focussed on finding and testing signals which show less or negligible fading. IRSL signals measured at elevated temperature following IR stimulation at 50°C (post-IR IRSL) have been shown to be much more stable than the low temperature IRSL signal and seem to have considerable potential for dating. For Early Pleistocene samples of both European and Chinese loess natural post-IR IRSL signals lying in the saturation region of the laboratory dose response curve have been observed; this suggests that there is no significant fading in nature. As a contribution to the further testing of post-IR IRSL dating, we have used 18 samples from two Japanese loess profiles for which quartz OSL and tephra ages up to 600 ka provide age control. After a preheat of 320°C (60 s), the polymineral fine grains (4–11 μm) were bleached with IR at 50°C (200 s) and the IRSL was subsequently measured at 290°C for 200 s. In general, the fading uncorrected post-IR IRSL ages agree with both the quartz OSL and the tephra ages. We conclude that the post-IR IRSL signal from these samples does not fade significantly and allows precise and accurate age determinations on these sediments.     

SIMS‐SS,A NEW OBSIDIAN HYDRATION DATING METHOD: ANALYSIS AND THEORETICAL PRINCIPLES*

The water diffusion mechanism in obsidian has been revisited with the advent of a new dating approach employing secondary ion mass spectrometry (SIMS). The water diffusion SIMS(+) profile and the concept of a surface saturation (SS) layer in obsidians both provide a sound basis for the new diffusion age equation (SIMS‐SS) and are supported by dated world examples ( Liritzis et al. 2004 ). Here, we present the basic physical–chemical analysis of the mass transport phenomenon on which the new dating method is based. The crucial age parameter of the SIMS‐SS dating approach for archaeological obsidians—that is, the surface saturation (SS) layer—is supported by both theoretical and experimental data.     

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.     

New age constraints for hominid footprints found on Jeju Island,South Korea

In 2004 numerous hominid footprints, along with diverse animal footprints, were found in the Late Quaternary strata of Jeju Island, South Korea. However, the age of the sediments in which the footprints were found is still controversial. Previous age estimates included radiocarbon ages of ca. 15,000 yr BP (Late Pleistocene) and quartz optically stimulated luminescence ages of ca. 7000 yr BP (mid-Holocene). In this study we report on 11 AMS ¹⁴C dating results from a new set of samples collected from the footprint-bearing strata and from associated sediments. Despite some variations and age reversal, all samples collected from the footprint-bearing strata yielded ¹⁴C ages of late Pleistocene. These ages are comparable with previous radiocarbon dating results. Furthermore, the presence of the proboscidean footprints attributable to woolly mammoths in the footprint-bearing strata supports the radiocarbon dating results. Based on the new radiocarbon dates and the presence of the alleged mammoth footprints, the age of the hominid footprints found at Jeju Island is thought to be late Pleistocene (about 19,000–25,000 cal yr BP). Therefore, this is the second discovery of hominid footprints dated to the Pleistocene age in Asia, and the first to be discovered in Korea.     

‘Old wood’ effect in radiocarbon dating of prehistoric cremated bones?

Numerous reports of successful radiocarbon dating of cremated bones have emerged during the last decade. The success of radiocarbon dating cremated bones depends on the temperature during burning and the degree of recrystallisation of the inorganic bone matrix. During cremation bones undergo major morphological and mineralogical changes which have raised some interesting questions and discussion on the origin of the carbon source in archaeologically cremated bones. Recent laboratory experiments reveal that the properties of the combustion atmosphere play a significant role regarding the source carbon in cremated bones. Thus radiocarbon dating cremated bones is potentially dating the wood used for the cremation fire. Here we compare a high precision radiocarbon dated human bone with an associated dendrochronological age from an oak coffin. We find that the age discrepancy between the dendrochronological age and the cremated bone of 73 ± 26 ¹⁴C yr is best accounted for by the so called ‘old wood’ effect.     

Proposing new approaches for dating young volcanic eruptions by luminescence methods

The application of luminescence dating to young volcanic sediments has been first investigated over three decades ago, but it was only with the technical innovations of the last decade that such analyses became viable. While current analytical procedures show promise for dating late Quaternary volcanic events, most efforts have been aimed at unconsolidated volcanic tephra. Investigations into direct dating of lava flows or of non-heated volcanoclastics like phreatic explosion layers, however, remain scarce. These volcanic deposits are of common occurrence and represent important chrono- and volcanostratigraphic markers. Their age determination is therefore of great importance in volcanologic, tectonic, geomorphological and climate studies. In this article, we propose the use of phreatic explosion deposits and xenolithic inclusions in lava flows as target materials for luminescence dating applications. The main focus is on the crucial criterion whether it is probable that such materials experience complete luminescence signal resetting during the volcanic event to be dated. This is argued based on the findings from existing literature, model calculations and laboratory tests.     

Radiocarbon dating by the accelerator technique

Radiometric dating of archaeological samples by the accelerator mass spectrometry (AMS) technique is well established today. The main advantage of this method compared to the old decay counting procedure is the small sample size (1 mg carbon equivalent weight) needed to carry out a dating. The basic principles as well as the present status of the technique are presented. Experiences from the first year of routine measurements in the Uppsala laboratory are discussed and some examples of the material analysed are given.     

Rock surface luminescence dating of prehistoric rock art from central Iberia

Rock art paintings are notoriously difficult to date numerically. Recently, luminescence dating has been shown to provide reliable rock surface burial ages in various archaeological settings. Here we use the cross-cutting relationship between a fallen rock and two paintings of the Iberian Levantine (older) and Schematic (younger) styles to constrain the age of the paintings by dating the rockfall event using rock surface luminescence dating. Infrared-stimulated luminescence (IRSL) signals as a function of depth into the buried face of the talus border indicate that the IRSL signal measured at 50°C (IR₅₀) was sufficiently reset to a depth of about 1.6 mm prior to burial. An uncorrected IR₅₀ age of 1.6 ± 0.2 ka was calculated for the rockfall event by dividing the surface equivalent dose (D_e) by the total dose rate. This age was corrected using both conventional and field-to-laboratory saturation approaches to yield indistinguishable ages of 2.7 ± 0.5 and 2.9 ± 0.3 ka, respectively. Since the panel with Schematic art was first available to the artist after the rockfall, we conclude the Schematic rock art at Villar del Humo is younger than ~2.9 ka. The Levantine rock art was painted on a panel constrained by the talus boulder before detachment, and so it is likely to be older than ~2.9 ka.     

A NEW THERMOLUMINESCENCE DATING TECHNIQUE FOR HEATED FLINT*

A new thermoluminescence (TL) technique for determining the age of heated flint artefacts from archaeological sites is presented. It is a variant of the SAR protocol, which is usually used for OSL dating of sediment, but it is not based on a presumed model for fitting the dose–response curve. Dose recovery tests as well as comparisons with standard protocols show the accuracy of the new technique. It is found that the sensitivity of the thermoluminescence (TL) signal of flint in the orange–red waveband does not show severe changes due to the heating process while measuring the TL. This allows the application of a short SAR procedure, which requires only two dose points. The technique does not require as much instrument time as other SAR techniques, and thus is advantageous for dating very old samples. The major advantage of this new technique is the small amount of sample material required, which allows the dating of samples that are too small for standard TL dating techniques.