Caves and rockshelters are critical loci for the analysis and understanding of human trajectories in the past. Use and re-uses of the same context, however, might have had serious impacts on depositional aspects. This is particularly true for the archaeological history of desert environments, such as the central Sahara, where most of the deposits are made of loose sand, rich in organic matter. Besides traditional stratigraphic reconstructions and a detailed study of the material culture, radiocarbon measurements from different contexts analyzing several types of material (bone, dried and charred coprolite, uncharred and charred plant remains, etc.) can highlight intrinsic critical aspects of 14C determinations. These measurements must be carefully evaluated to provide a correct chronological assessment of the life history of the site. We present the statistics derived from the set of about 50 14C measurements from the site of Takarkori, southwest Libya, where early Holocene foragers and then groups of cattle herders inhabited the area from ∼10,200 to 4600 cal yr BP. We have used the BCal Bayesian 14C calibration program designed for statistical presentation of the calibrated data and the estimation of their probability for different phases. Results indicate that the Takarkori rockshelter was occupied during 4 phases of the following cultures: Late Acacus from 10,170 to 8180 cal yr BP; Early Pastoral, 8180–6890 cal yr BP; Middle Pastoral, 7160–5610 cal yr BP; and Late Pastoral, 5700–4650 cal yr BP.

This paper discusses the chronology of burial grounds containing specific Seima-Turbino type bronze weaponry (spears, knives, and celts). The “transcultural” Seima-Turbino phenomenon relates to a wide distribution of specific objects found within the sites of different Bronze Age cultures in Eurasia, not immediately related to each other. The majority of the Seima-Turbino objects represent occasional findings, and they are rarely recovered from burial grounds. Here, we present a new set of 14C dates from cemeteries in western Siberia, including the key Asian site Rostovka, with the largest number of graves containing Seima-Turbino objects. Currently, the presented database is the most extensive for the Seima-Turbino complexes. The resulting radiocarbon (14C) chronology for the western Siberian sites (22nd–20th centuries cal BC) is older than the existing chronology based on typological analysis (16th–15th centuries BC) and some earlier 14C dates for the Seima-Turbino sites in eastern Europe. Another important aspect of this work is 14C dating of complexes within specific bronze objects—daggers with figured handles—which some researchers have related to the Seima-Turbino type objects. These items are mostly represented by occasional finds in Central Asia, however, in western Siberia these have been recovered from burials, too. The 14C dating attributes these daggers to the end of the 3rd millennium cal BC, suggesting their similar timing to the Seima-Turbino objects. Further research into freshwater reservoir offsets in the region is essential for a more reliable reconstruction of the chronology of the Seima-Turbino phenomenon and the daggers with figured handles.

Mazar and Bronk Ramsey (2008) recently proposed that the Iron I/IIA transition in the Levant took place during the first half of the 10th century. In the first part of this article, we challenge their method and conclusions. We argue against the inclusion of charcoal in their model, which could lead to an “old wood effect.” We also argue that in dealing with a transition date, all available data must be taken into consideration. In the second part of the article, we propose Bayesian Model I for the Iron I/IIA transition, which is based on 2 sets of data—for the periods immediately before and after this transition. Our model, along with the other 11 published Bayesian models for this transition that used only short-lived samples, agrees with the Low Chronology system for the Iron Age strata in the Levant and negates all other proposals, including Mazar's Modified Conventional Chronology. The Iron I/IIA transition occurred during the second half of the 10th century. In the third part of the article, we present a new insight on the Iron I/IIA transition. We propose that the late Iron I cities came to an end in a gradual process and interpret this proposal with Bayesian Model II.

Mazar and Bronk Ramsey (2008) recently challenged Sharon et al. (2007; also Boaretto et al. 2005) and us (e.g. Finkelstein and Piasetzky 2003, 2007a,b) regarding the date of transition from the Iron I to the Iron IIA in the Levant. While we and Sharon et al. placed this transition in the second half of the 10th century BCE, Mazar and Bronk Ramsey positioned it “during the first half of the 10th century BCE” and argued that “the second half of the 10th century BCE should be included in the Iron IIA” (Mazar and Bronk Ramsey 2008:178). We discuss some problems in the methodology of Mazar and Bronk Ramsey that may have influenced their results. In particular, we discuss 1) the exclusion of data; 2) the inclusion of data (charcoal samples); and 3) show that even according to Mazar and Bronk Ramsey, excluding these samples position the late Iron I/IIA transition in the late 10th century. Finally, we present our own 2 Bayesian models for the Iron I/IIA transition.

The majority of samples processed at the National Ocean Sciences AMS Facility (NOSAMS) thus far were collected as part of the World Ocean Circulation Experiment (WOCE). Due to the long storage time (2–3 yr) required to analyze thousands of samples on the accelerator mass spectrometer (AMS), a test was designed and implemented to determine the effects, if any, of storage time on 14C concentration. We find no systematic offsets in AMS measurements made over a 5-yr period between a total of 16 replicate sets from surface and deep water collected at the same locality. Furthermore, the average δ14C value from the deepwater AMS replicates (-213.1%, std. dev. 7.3) agrees very closely with the conventional 14C results published for GEOSECS (-212.7%) from station 320 taken 20 yr earlier.

A total of 73 WOCE shipboard replicate sets (162 AMS measurements) were analyzed with a mean precision of 4.3%. AMS results from 20 more shipboard replicate sets (44 AMS measurements) submitted as CO2 from the Stable Isotope Laboratory (SIL) at the University of Washington were analyzed with a mean precision of 3.4%. These results suggest no significant difference between water stripping methods used in each preparation lab.

To assess reproducibility, we calculate a pooled estimate of σ for replicates called s, which we use as an approximation of σTOT for a given sample type. The s for WOCE seawater replicates is 4.9% and 5.8% for SIL gas replicates. These numbers demonstrate an overall reproducibility of seawater AMS results at NOSAMS that is in line with reported errors. We take the difference between total error s and machine error as the overall standard deviation of combined uncertainties associated with preparation of samples and with AMS. For seawater samples processed at NOSAMS, σSPL is calculated to be 2.4%, and for the SIL gas replicates it is 4.8%.

Reproducibility of samples prepared with an acid hydrolysis technique is demonstrated using 24 coral samples submitted in triplicate by Dr. R. G. Fairbanks of Lamont Doherty Earth Observatory. Seventy-two replicates were prepared and analyzed at NOSAMS with a mean reported precision of 1.2%. The pooled estimate s for the Fairbanks triplicates is 2.6%. We calculate a laboratory reproducibility uncertainty for coral hydrolysis samples of 2.2%.

In 1993, NOSAMS participated in the Third International Radiocarbon Intercomparison (TIRI) Study. We report here 60 AMS analyses of the six TIRI test materials, five of which are organic carbon samples, to validate sample-processing methods for organic carbon sample AMS analyses at NOSAMS.

When humans consume foods from different radiocarbon reservoirs offset in age to the atmosphere, inaccuracies in the 14C date of bone collagen can occur. Mesolithic human skeletons from the Iron Gates section of the Lower Danube Valley have yielded reservoir offsets of up to ∼500 yr. This has been demonstrated through direct dating of bulk collagen from human bones and the remains of ungulate bone projectile points that were found embedded in them (Cook et al. 2001). We present improvements to a novel HPLC method for the detection and separation of underivatized amino acids using a water-only mobile phase free of organic or inorganic modifiers, ensuring very low carbon backgrounds. Our hypothesis is that direct 14C dating of single essential and non-essential amino acids might allow an improvement in the dating accuracy for reservoir-affected human bones. The method facilitates separation of less polar amino acids (mostly “essential”), currently not possible in the recently published protocol. We discuss methodological developments, demonstrate carbon backgrounds, and present analytical approaches to minimize their effects. We validate the precision and accuracy of the method by accelerator mass spectrometry (AMS) dating relatively modern and 14C-dead, known-age bone standards. Finally, we apply the method to the dating of single amino acids from bone samples with a proven ∼500–yr carbon reservoir effect from Mesolithic burials at the Iron Gates sites. We investigate whether differences can be found in AMS dates for essential and non-essential amino acids since, although contemporaneous, these are expected to derive from dietary sources with differing 14C reservoirs.

Tritium time series for precipitation in Beijing have been reconstructed for the period 1953–2002 using various methods: Guanbingjun method; trend surface analysis method; double reference curve method; triangulation method; and correlation method. By comparing the reconstructed results with the measured data of Beijing as well as data of other regions available in the IAEA GNIP database, the corresponding tritium time series have been developed for Beijing for the period 1953–2002, and the optimal time series was selected. The reconstructed result can be used for groundwater dating and related studies in Beijing as well as the surrounding areas.

The tree-ring program at Belfast originally aimed at the construction of a 6000-year oak chronology. The stimulus for this work came from the large numbers of sub-fossil oaks uncovered in Northern Ireland during land drainage and motorway construction in the late 1960's (Pilcher et al 1977). It became clear that any attempt to build such a long chronology would break naturally into two distinct units. One unit related to the construction of a prehistoric (BC era) chronology dependent on the sampling of large numbers of essentially random sub-fossil timbers. For this unit to be successful, timbers would have to survive relatively uniformly through time. The second chronology building unit was related principally to the AD era, with a natural extension into the first millennium BC at least. This unit was envisaged as the link between the present day and the necessarily floating sub-fossil chronologies. This AD chronology was based on modern, historic, and archaeologic timbers.

This list includes samples completed to July, 1972. All samples are counted for at least 2500 min., and X2 analyses are made on 100-min. print-outs. Errors quoted are 1σ, derived from sample, background, and NBS oxalic acid standard measurements, adjusted where appropriate for small-sample dilution.

The transformation of radiocarbon years to calendar years (cal AD/BC) is not straightforward because of past variations in atmospheric 14C content (de Vries 1958; Suess 1970). A calibration curve, y = f(x), transforms each dendrochronologically dated calendar age (x) to a 14C date (y). By inverting this relationship, one can determine the calibrated calendar age of a given sample. In some time intervals, the calibration curve is problematic in that f(x) is not uniquely invertible (Fig. 1); even an exact measurement of y cannot be converted to a single calendar age (see examples in van der Plicht & Mook (1987)).

Annually resolved radiocarbon (14C) measurements on tree rings led to the discovery of abrupt variations in 14C production attributed to large solar flares. We present new results of annual and subannual 14C fluctuations in tree rings from a middle-latitude sequoia (California) and a high-latitude pine (Finland), analyzed for the period 1030–1080 CE, to trace a possible impact of the Crab supernova explosion, occurring during the Oort minimum of solar activity. Our results indicate an increase of Δ14C around 1054/55 CE, which we estimate is higher in magnitude than the cyclic variability due to solar activity at a 2σ significance level. The net signal appears to be synchronized in the studied locations. Several sources of this event are possible including γ-rays from the Crab supernova, an unusually weak solar minimum or a solar energetic particle incident. More data are needed to provide more insight into the origin of this 14C event.

A reanalysis of the chronology of Pololu Valley, located in the district of Kohala on Hawai'i Island, is presented using standard radiocarbon and accelerator mass spectrometry (AMS) dating. Using curated materials from the 1970s, Pololu is reassessed and found to have the earliest coastal occupations in this part of Hawai'i, beginning about AD 1300. Occupations at the dunes and in the valley interior are investigated, as are dryland and wetland field agricultural systems. These data provide a refined model for expansion and intensification of agricultural production in the 15th–17th centuries, and link this remote valley to demographic and sociopolitical trends that were occurring in the rest of Hawai'i.

This date list includes all samples processed from December 1970 through November 1971 at the Illinois State Geological Survey Radiocarbon Dating Laboratory. The benzene liquid scintillation method of Noakes, Kim, and Stipp (1965), and Noakes, Kim, and Akers (1967) was used. A new benzene synthesis system has been completed, and several changes in the sample preparation procedure have been made since the last date list report (Coleman, 1972). A brief summary of the benzene synthesis and sample pretreatment techniques used to determine the dates reported here follows.

In this study, molluscan shells housed at the University Museum, the University of Tokyo, provided a new set of region-specific correction values (ΔR) for the western Pacific, in particular for the central part of the main islands in the Japanese Archipelago and the southwest islands of Japan. The values of 40 total samples were calculated from 11 regions. North of the main islands and in the Ryukyu Islands, the mean ΔR values showed comparatively small values, 5–40 14C yr; in the central part of the main islands, these values were 60–90 14C yr.

The College of Engineering Research Division radiocarbon dating laboratory began operating in November 1962 employing a Sharp Laboratories, Inc., CDL-14 system based upon the methane method of Fairhall, Shell, and Takashima (1961).

Dates reported herein are calculated using a 5568 yr C14 half-life. The modern standard is taken as 95% of the NBS oxalic acid C14 standard which is converted to CO2 followed by conversion to CH4 in the manner of Fairhall et al. The errors quoted are the 1 σ statistical errors.

Appropriate management strategies are essential for the protection and maintenance of groundwater resources. It is therefore important that aquifers are understood in terms of hydraulics, recharge, and yield potential, and that the vulnerability of aquifers to surface pollution is evaluated. A range of aquifer types were examined in this study, and water samples were analyzed for the radiocarbon content of the total dissolved inorganic carbon (TDIC), stable isotopes, and a suite of chemical and physical parameters. The data were input to a selection of models for the estimation of the initial activity of the TDIC, and groundwater ages were calculated. Eight commonly used models were comparatively assessed in the study. The Tamers, Mook, and IAEA models gave anomalous ages, probably because of their inability to correct for solid phase isotopic exchange in aquifers. The Pearson, F&G, Evans, Eichinger, and Mass Balance models produced results in broad agreement.

The study shows that contrary to popular belief, there are sources of ancient groundwater in Ireland. Of the 19 sampling stations, two boreholes yielded waters with age estimates of greater than 10,000 BP. Water samples from a further six sites returned ages of between around 800 and 4000 BP. In contrast to borehole samples, spring wells yielded water of consistently young ages, demonstrating rapid recharge and flow mechanisms. Samples from several spring wells produced negative ages, indicating the presence of anthropogenic 14C. The findings demonstrate the potential for contamination of springs by surface runoff, while sources of greater age generally offer a greater degree of protection from surface pollution.

Origins of carbon in potsherds are studied through field experiments which involve firing pots containing selected components and laboratory analyses. As temper seems to be the main source of carbon, radiocarbon dates may be too old if calcium carbonate is used. We can avoid the carbon from the clay by low-temperature burning of samples.

Regional levels of radiocarbon have been monitored in order to investigate the impact of fossil fuel combustion on the activity of atmospheric 14CO2 in central Europe. Data from atmospheric 14CO2 monitoring stations in the Czech Republic, Slovakia, and Hungary for the period 2000–2008 are presented and discussed. The Prague and Bratislava monitoring stations showed a distinct local Suess effect when compared to the Jungfraujoch clean-air monitoring station. However, during the summer period, statistically insignificant differences were observed between the low-altitude stations and the high-mountain Jungfraujoch station. 14C data from the Hungarian monitoring locality at Dunaföldvár and the Czech monitoring station at Košetice, which are not strongly affected by local fossil CO2 sources, indicate similar grouping and amplitudes, typical for a regional Suess effect.

A high-resolution age model was developed for Kettle Lake, North Dakota, USA, from a series of 53 accelerator mass spectrometry (AMS) radiocarbon ages calibrated with Bayesian statistical methods, which provide a monotonically increasing series of calibrated ages with depth. Evident in the sediment are several slumps, debris flows, or landslides, which are confirmed by 14C dating. Removal of these facies produces a continuous sedimentary sequence for the past 13,000 yr with exception of one ≃260-yr hiatus associated with a 1.5-m-thick slump deposit. All ages except one are on terrestrial macrofossils and charcoal. A test age on aquatic organic detritus shows a hardwater effect of 600 yr at ≃2000 cal BP. Two ages from the same level on herbaceous charcoal and Chenopodium seeds are statistically the same, which further demonstrates the suitability of charcoal from grassland environments for AMS 14C age control. However, 2 specimens of wood charcoal are too old relative to bracketing ages and glacial geologic history. These ages confirm the sedimentary interpretation of redeposition and provide a caution about the longevity of wood charcoal in the environment and its suitability for age control in lacustrine sediments.

Data on radiocarbon (14C), 137Cs, 210Pb, and 241Am levels in an ombrotrophic peat sequence from a montane site on the east coast of Ireland are compared with data from a similar sequence at an Atlantic peatland site on the west coast. The 14C profiles from the west and east coasts show a broadly similar pattern. Levels increase from 100 pMC or less in the deepest horizons examined, to peak values at the west and east coast sites of 117 ± 0.6 pMC and 132 ± 0.7 pMC, respectively (corresponding to maximal fallout from nuclear weapons testing around 1964), thereafter diminishing to levels of 110–113 pMC near the surface. Significantly, peak levels at the east coast site are considerably higher than corresponding levels at the west coast site, though both are lower than reported peak values for continental regions. The possibility of significant 14C enrichment at the east coast site due to past discharges from nuclear installations in the UK seems unlikely. The 210Pbex inventory at the east coast site (6500 Bq m−2) is significantly higher than at the west coast (5300 Bq m−2) and is consistent with the difference in rainfall at the two sites. Finally, 137Cs and 241Am inventories at the east coast site also exceed those at the west coast site by similar proportions (east:west ratio of approximately 1:1.2).

Tree-ring series were collected for radiocarbon analyses from the vicinity of Paks nuclear power plant (NPP) and a background area (Dunaföldvár) for a 10-yr period (2000–2009). Samples of holocellulose were prepared from the wood and converted to graphite for accelerator mass spectrometry (AMS) 14C measurement using the MICADAS at ETH Zürich. The 14C concentration data from these tree rings was compared to the background tree rings for each year. The global decreasing trend of atmospheric 14C activity concentration was observed in the annual tree rings both in the background area and in the area of the NPP. As an average of the past 10 yr, the excess 14C emitted by the pressurized-water reactor (PWR) NPP to the atmosphere shows only a slight systematic excess (∼6′) 14C in the annual rings. The highest 14C excess was 13′ (in 2006); however, years with the same 14C level as the background were quite frequent in the tree-ring series.