This paper presents 14C, 13C and chemical data of soil organic matter (SOM) in three soil profiles under native forests from Brazil: Londrina (southern), Piracicaba (southeastern) and Altamira (northern). The main objective is to use carbon isotopes in tropical and subtropical soils of Brazil to provide information about vegetation changes that occurred in relation to climate changes during the Holocene. 14C data from SOM indicate that the organic matter in the soils studied is of at least Holocene age. 13C data indicate that C4 plants probably provided the dominant vegetation in Londrina and Piracicaba during the early and mid-Holocene and that C3 plants provided the dominant vegetation in the Altamira region during the Holocene.

We report on 69 radiocarbon dates of mollusk shells and benthic foraminifera from the upper 132 m of the marine shelf sediments of the Skagen Core (220 m total length). The dated sequence covers the Late Glacial and the Holocene (from 15 ka bp to Recent). Sedimentation rates range from 1 to 70 m ka−1. The macrofossil shell dates follow a smooth curve constituting an age model for dating the sediments. The foraminiferal dates fall into two groups: those that agree exactly with the mollusk shells and those that deviate substantially, always being older than the shells by as much as 5 ka. One mixed foraminiferal sample consisted of members from both groups, and as a result, the age deviation of the sample turned out to be some weighted average. The data indicate that the age deviations are due to admixtures of reworked older foraminifera.

For the Bronze Age Catacomb cultures of the North-West Caspian steppe area in Russia, there is a conflict between the traditional relative archaeological chronology and the chronology based on radiocarbon dates. We show that this conflict can be explained largely by the fact that most dates have been obtained on human bone material and are subject to 14C reservoir effects. This was demonstrated by comparing paired 14C dates derived from human and terrestrial herbivore bone collagen. In addition, values of stable isotope ratios (δ13C and δ15N) and analysis of food remains from vessels and the stomach contents of buried individuals indicate that a large part of the diet of these cultures consisted of fish and mollusks, and we conclude that this is the source of the reservoir effect.

Most of the 14C measurements reported here were made between October 1974 and October 1975. Equipment, measurement, and treatment of samples are the same as reported previously (R, 1968, v 10, p 36-37) except for bone samples (see below).

Solar activity, as expressed by interplanetary solar wind magnetic field fluctuations, modulates the atmospheric production of 14C. Variations of atmospheric 14C can be precisely established from the cellulose within annual tree rings, an independently dated conservative archive of atmospheric carbon isotopes. Δ14C time series interpretation shows that solar activity has varied with a recurrence period of 2115 ± 15 (95% confidence) yr (Hallstattzeit) (Damon & Sonett 1991) over the past 7160 yr. From a non-stationary oscillation solar activity hypothesis, 52 possible spectral harmonics may result from this period. Damon and Sonett (1991) identify powerful harmonics such as the 211.5-yr (Suess) and the 88.1-yr (Gleissberg) cycles as independent fundamental periods. These stronger harmonics appear to modulate the 11-yr (Schwabe) sunspot cycle. Variations in the solar magnetic field, thus, may respond to longer period variations of the solar diameter envelope (Ribes et al. 1989). Such variations would affect solar radiative energy output and, consequently, change total solar irradiance (Sofia 1984).

Radiocarbon analyses have been performed at Isotopes, Inc. since 1957 using proportional-counting techniques. Carbon dioxide is employed as the counting gas at pressures up to two atmospheres. The counter presently in service is electrolytic copper and has an active volume of just under two liters. It is shielded by one in. of mercury, a ring of 23 G-M counters operated in anti-coincidence with the sample counter, 4 in. of paraffin wax, and 18 in. of hot-rolled steel. A background of 9.2 counts/min has been attained with this arrangement.

A system with several lines for the preparation of graphite targets for radiocarbon analysis has been built at the new accelerator mass spectrometry (AMS) facility in Caserta, Italy. Special attention has been paid in the design to the reduction of background contamination during sample preparation. Here, we describe the main characteristics of these preparation lines. Results of tests performed to measure 14C background levels and isotope fractionation in several blank samples with the Caserta AMS system are presented and discussed.

In the framework of the European Research Council-funded project, “Reconstructing Ancient (Biblical) Israel: The Exact and Life Sciences Perspective,” we carried out multiple analyses on iron and bronze objects from provenanced contexts in Israel, as well as on previously unidentified metallurgical remains from the production of both metals. In addition, we counted anew iron and bronze objects from well-stratified contexts and studied metalworking sequences at major sites, which included those that had undergone the bronze/iron transition. This enabled us to clarify some of the issues related to the bronze/iron transition in the southern Levant. Using this evidence, we showed that iron was not used for utilitarian purposes before the Iron I (late 12th century BCE) and that iron only became dominant concurrently with the beginning of its systematic production during the Iron IIA (10th–9th centuries BCE). A strong correlation between iron and bronze production suggests that during the Iron I local independent bronzesmiths adopted the new iron technology. Under local administrations that developed during the Iron IIA, workshops that previously produced bronze turned to iron production, although they continued to manufacture bronze items as a secondary venture. Significantly, at some of the major urban centers iron production was an independent industry that included the entire operational sequence, including the on-site smelting of the ore. This development appears to have been a major contributor to the transition to systematic production of iron.

The long 14C chronologies currently used as calibration curves combine results from wood that grew in the western United States, the British Isles and Germany. Although these results show few significant differences in the 14C content of contemporaneous wood when averaged over the length of the chronology (i.e., the means of overlapping sections of chronology are the same), closer examination shows considerable variability. Separating the sections of chronology according to the provenance of the wood used for calibration reveals patterns that suggest small but finite differences in the 14C content of wood from different locations. We conclude that there is some evidence that German and American wood give dates older by between 20 and 40 yr from those of Irish oak for some periods. Additionally we suggest that the shift of the Belfast 1986 calibration data by ca. 18 yr toward older dates may not be valid and that the resultant offset between the Belfast 1986 and Seattle 1993 data shows a small but real difference in the 14C content of contemporaneous American, German and Irish wood. Intralaboratory measurements made in Belfast on contemporaneous German and Irish oak, and bristlecone pine and Irish oak, give offsets of 39 and 41 yr, respectively, with the Irish oak dating younger. Previous studies, in which sample pairs of American and English and French wood were processed in the same laboratory, also showed American wood to be slightly depleted in 14C. None of the findings of this study would significantly alter calibrated 14C dates.

Accelerator mass spectrometric (AMS) radiocarbon analyses of live-collected, prebomb samples of shell carbonates of the land snails Rabdotus dealbatus and R. alternatus from Texas were carried out to quantify the characteristic age anomalies of land snails from limestone areas. Age anomalies are similar for the two species; they average +700 yr and vary by ±180 yr (1σ) among samples. Serial analysis of 1 shell reveals a significant ontogenetic trend in 14C age anomalies, with older apparent ages (up to 1200 yr) in the apical part of the shell and younger and uniform ages in the last whorl. No trend in age anomalies was found across a broad range of rainfall conditions (from 300 to 1000 mm mean annual rainfall).

It is now almost 10 yr since radiocarbon dating of cremated bone was first developed using the small carbonate component contained within the hydroxyapatite-based inorganic fraction. Currently, a significant number of 14C laboratories date cremated bone as part of their routine dating service. As a general investigation of cremated bone dating since this initial development, a small, cremated bone intercomparison study took place in 2005, involving 6 laboratories. Six cremated bone samples (including 2 sets of duplicates), with ages spanning approximately 1500–2800 BP, were sent to the laboratories. The results, which showed relatively good agreement amongst the laboratories and between the duplicate samples, are discussed in detail.

We assessed the evidence for variations in the marine radiocarbon reservoir effect (MRE) at coastal, archaeological Iron Age sites in north and west Scotland by comparing AMS measurements of paired marine and terrestrial materials (4 pairs per context). ΔR values were calculated from measurements on material from 3 sites using 6 sets of samples, all of which were deposited around 2000 BP. The weighted mean of the ΔR determinations was −79 ± 17 14C yr, which indicates a consistent, reduced offset between atmospheric and surface ocean 14C specific activity for these sites during this period, relative to the present day (ΔR = ∼0 14C yr). We discuss the significance of this revised ΔR correction by using the example of wheelhouse chronologies at Hornish Point and their development in relation to brochs. In addition, we assess the importance of using the concepts of MRE correction and ΔR variations when constructing chronologies using 14C measurements made on materials that contain marine-derived carbon.

Calibration (using CALIBomb) of radiocarbon measurements made on the enamel of human teeth from people born during the nuclear era typically produce 2 possible age ranges that potentially reflect the period of tooth formation. These ranges correspond to periods before and after the 1963 atmospheric 14C maximum. Further measurements made on the collagen component of the combined dentine and cementum from the roots of the same teeth enable the appropriate age range to be selected. Using this range and the formation times for individual teeth, we estimated the year of birth of the individuals and compared these to the known dates of birth. The results were relatively accurate and confirmed those of a previous study by another research group. The present study demonstrates that it is possible to produce a good estimate of the year of birth from a single tooth.

The dating of South African rock art using radiocarbon is a considerable challenge and only 1 direct date has so far been obtained, on black pigments from Sonia's Cave Upper, Boontjieskloof. The main problem with direct dating these paintings is the presence of calcium oxalates behind, on, and within the pigment layers. Calcium oxalates are formed through lichen and bacterial action on the rock face. These reactions can sometimes take place over long periods and can incorporate carbon of a younger age into the pigments. This study aims to date black pigments from a rockshelter, RSA TYN2 (Eastern Cape, South Africa), by removing the calcium oxalate contamination. Two different protocols were tried: density separation and acidification. The latter successfully removed calcium oxalates and was therefore applied to 3 black pigment samples from the rockshelter. After acid pretreatment, accelerator mass spectrometry (AMS) dating was undertaken on the remaining residues. Three results were obtained (2072 ± 28 BP, 2100 ± 40 BP, and 2083 ± 32 BP), which constitute the oldest results so far obtained for direct dates on South African rock art. The most likely calibrated date range for the painting at this site is between 2120 and 1890 cal BP. The ages are in close agreement with each other and this consistency suggests that our preparation protocol has successfully removed the majority of the carbon contaminants.

Holocene sedimentary and geomorphic sequences from the Dead Sea region, Israel, are compared by correlation of more than 50 radiocarbon dates. The 14C dates provided the chronological basis that enabled us to detect basin-scale events that are hard to ascertain in single-site records. This paper is the first attempt to compare different Holocene records from several sites along the Dead Sea, based on their chrono-stratigraphy. Included is the first publication of the paleoclimatic record of the Nahal Darga ephemeral stream valley. Such a regional compilation is needed, because only the integration and comparative evaluation of several records can produce a reliable climatic history by establishing the height of former Dead Sea levels that may be complicated by tectonics and the rise of Mount Sedom. A relatively high level of the Holocene Dead Sea occurred during the mid-Holocene around 4400 BP or about 3000 cal BCE after calibration. The lake level fell sharply around 4000 BP, i.e. 2500 cal BCE, and later fluctuated close to early 20th century levels. The 14C-based correlation is also used to estimate the rising rates of the Mount Sedom salt diapir that are apparently smaller than 10 mm per year.

This paper examines 2 potential sources of the radiocarbon offset between human and terrestrial mammal (horse) bones recovered from Norse (∼AD 870–1000) pagan graves in Mývatnssveit, north Iceland. These are the marine and freshwater 14C reservoir effects that may be incorporated into human bones from dietary sources. The size of the marine 14C reservoir effect (MRE) during the Norse period was investigated by measurement of multiple paired samples (terrestrial mammal and marine mollusk shell) at 2 archaeological sites in Mývatnssveit and 1 site on the north Icelandic coast. These produced 3 new δR values for the north coast of Iceland, indicating a δR of 106 ± 10 14C yr at AD 868–985, and of 144 ± 28 14C yr at AD 1280–1400. These values are statistically comparable and give an overall weighted mean δR of 111 ± 10 14C yr.

The freshwater reservoir effect was similarly quantified using freshwater fish bones from a site in Mývatnssveit. These show an offset of between 1285 and 1830 14C yr, where the fish are depleted in 14C relative to the terrestrial mammals. This is attributed to the input of geothermally derived CO2 into the groundwater and subsequently into Lake Mývatn. We conclude the following: i) some of the Norse inhabitants of Mývatnssveit incorporated non-terrestrial resources into their diet that may be identified from the stable isotope composition of their bone collagen; ii) the MRE off the north Icelandic coast during the Norse period fits a spatial gradient of wider North Atlantic MRE values with increasing values to the northwest; and iii) it is important to consider the effect that geothermal activity could have on the 14C activity of samples influenced by groundwater at Icelandic archaeological sites.

In conformance with the request of the editors, ages in this date list have been calculated with the Libby half life value of 5568 ± 30 yr, although the present best estimate of the half life value is 5730 ± 40 yr (Godwin, 1962). Additional support for the latter value as being closer to the “effective” value for dating has been obtained by the measurements of samples of known age.

This research presents the first comprehensive radiocarbon chronology for central Alaska, encompassing the late Pleistocene and Holocene archaeological record. Dated component distributions, comprised of 274 14C dates from 160 components, indicate changing land-use strategies and subsistence economies, reflecting primarily lowland exploitation of bison, wapiti, and birds prior to 6000 cal B P, followed by increasing caribou and fish exploitation and use of upland areas. Microblade technology is conserved from the earliest components to ~1000 cal B P, and this continuity is not reflected in current cultural history sequences. Using component abundance as a proxy for population, initial colonization is associated with climate amelioration after ~14,000 cal BP, and population declines are associated with the Younger Dryas (13,000–12,000 cal BP) and initial establishment of widespread spruce forests (10,000–9000 cal BP).

The first meeting of the IntCal04 working group took place at Queen's University Belfast from April 15 to 17, 2002. The participants are listed as co-authors of this report. The meeting considered criteria for the acceptance of data into the next official calibration dataset, the importance of including reliable estimates of uncertainty in both the radiocarbon ages and the cal ages, and potential methods for combining datasets. This preliminary report summarizes the criteria that were discussed, but does not yet give specific recommendations for inclusion or exclusion of individual datasets.

All measurement is subject to error, which creates uncertainty. Every time that an analytical radiocarbon measurement is repeated under identical conditions on an identical sample (even if this were possible), a different result is obtained. However, laboratories typically make only 1 measurement on a sample, but they are still able to provide an estimate of the analytical uncertainty that reflects the range of values (or the spread) in results that would have been obtained were the measurement to be repeated many times under identical conditions. For a single measured 14C age, the commonly quoted error is based on counting statistics and is used to determine the uncertainty associated with the 14C age. The quoted error will include components due to other laboratory corrections and is assumed to represent the spread we would see were we able to repeat the measurement many times.

Accuracy and precision in 14C dating are much desired properties. Accuracy of the measurement refers to the deviation (difference) of the measured value from the true value (or sometimes expected or consensus value), while precision refers to the variation (expected or observed) in a series of replicate measurements. Quality assurance and experimental assessment of these properties occupy much laboratory time through measurement of standards (primary and secondary), reference materials, and participation in interlaboratory trials. This paper introduces some of the most important terms commonly used in 14C dating and explains, through some simple examples, their interpretation.