Pachacamac, covering an area of about 600 hectares (ha) near the Pacific shore, is one of the largest and most important archaeological sites in Peru. Most of the monumental adobe-made buildings of the later pre-Inca period (or Late Intermediate Period, about 10th–15th century AD) are so-called pyramids with ramps (the role of the ramps has been interpreted in different ways). Precise dating of the pyramids appears as a crucial step in defining the functions of Pachacamac in pre-Inca times. In this paper, we present the results obtained from 3 field campaigns at Pyramid III, one of the biggest buildings of the site. A total of 24 radiocarbon datasets from 4 different laboratories will help us to place the various steps of development of Pyramid III on a timescale, defined on the basis of the excavations. More absolute dates are available from another pyramid with ramps, which allow us to make comparisons and propose a new model of interpretation for the Pachacamac site during the Late Intermediate Period (LIP).

This paper contains 14C results obtained by the special high-precision proportional gas counter, designed by Tans and Mook (1978), on tree rings from the South German oak chronologies: Donau 7, 3, 10, and 12, originating from the Danube River basin (48° 24’ N, 10° 5’ E).

The direct carbonate procedure for accelerator mass spectrometry radiocarbon (AMS 14C) dating of submilligram samples of biogenic carbonate without graphitization is becoming widely used in a variety of studies. We compare the results of 153 paired direct carbonate and standard graphite 14C determinations on single specimens of an assortment of biogenic carbonates. A reduced major axis regression shows a strong relationship between direct carbonate and graphite percent Modern Carbon (pMC) values (m = 0.996; 95% CI [0.991–1.001]). An analysis of differences and a 95% confidence interval on pMC values reveals that there is no significant difference between direct carbonate and graphite pMC values for 76% of analyzed specimens, although variation in direct carbonate pMC is underestimated. The difference between the two methods is typically within 2 pMC, with 61% of direct carbonate pMC measurements being higher than their paired graphite counterpart. Of the 36 specimens that did yield significant differences, all but three missed the 95% significance threshold by 1.2 pMC or less. These results show that direct carbonate 14C dating of biogenic carbonates is a cost-effective and efficient complement to standard graphite 14C dating.

Sub-fossil sections from a Florida wetland were accelerator mass spectrometry (AMS) dated and the sedimentological conditions were determined. 14C data were calibrated using a combined wiggle-match and 14C bomb-pulse approach. Repeatable results were obtained providing accurate peat chronologies for the last 130 calendar yr. Assessment of the different errors involved led to age models with 3–5 yr precision. This allows direct calibration of paleoenvironmental proxies with meteorological data. The time frame in which 14C dating is commonly applied can possibly be extended to include the 20th century.

Dendrochronological studies are being carried out on two conifer species in the Stanley River area of western Tasmania. The chronology for Huon pine (Lagarostrobos franklinii), with living trees up to 1400 yr old, extends back to 571 bc. Living celery-top pine (Phyllocladus aspleniifolius) trees are up to 500 yr old. Apart from living or recently felled trees, sections have been taken from 350 subfossil logs preserved in floodplain sediments. They range in age from >38 ka to modern, with good coverage for the periods 9–3.5 ka and from 2.5 ka to the present. We report here on 14C measurements of decadal samples from three early Holocene logs, between 10 and 9 ka bp, providing short (ca. 300-yr) records of atmospheric 14C variations when plotted against ring numbers. The southern hemisphere data from Tasmania can be compared and wiggle-matched with published 14C calibration curves from German oak and pine. One set of measurements covers the period, ca. 9280–8990 cal bp, overlapping the link between the Hohenheim “Main 9” and middle Holocene master oak chronologies. The other sets of measurements from Tasmania coincide; they span the period, ca. 9840–9480 cal bp, overlapping the end of the German Preboreal pine and the beginning of the oak chronologies. Our measurements confirm that this part of the calibration curve is a gently sloping 14C-age plateau (ca. 8900–8700 bp, between 10,000 and 9500 cal bp), and suggest interhemispheric 14C differences close to zero.

Results of absolute age determination by the radiocarbon method, obtained in the Radiocarbon Laboratory of the Vernadsky Institute are given in this article. The counting of natural C14 activity was realized by measuring the gaseous carbon compounds—CO2 and C2H6—with the aid of a proportional counter. Investigation objects were wood, peat, coal, plant and animal remains and other organic material. All samples were preliminarily treated with hot 2% NaOH and 5% HCl to remove foreign humic acid and carbonate. Carbon dioxide, which was obtained after burning, was freed of electronegative admixtures by purification with the aid of CaO. Ethane was synthesized from the sample carbon through the following stages: natural sample→CO2→CaCO3→CaC2→C2H2→C2H6. The counting gas was let into the counter up to a pressure of 2 atm. Counters of stainless steel or copper of different volumes from 0.5 to 2 litres were used. The screening of the counters was effected by steel (24 cm thick) and mercury (2.5 cm thick) shields; the counter together with the mercury shield was enclosed in a circle of Geiger counters of the GS-60 type arranged in anti-coincidence. A detailed description of the methods, the constructions and the apparatus has been published (Vinogradov, Devirts, Dobkina, Markova, Martishchenko, 1961).

Authigenic micrite from a playa in the northern Sahara has been dated by both the U/Th and 14C methods. The U/Th ages can be a few thousand years greater or less than the 14C ages obtained on the smallest crystals of micrite. The latter are considered to form a reasonable chronology for the Holocene deposits. The deviations of the U/Th ages are explained by quantifiable losses and gains of uranium under changing redox conditions. Under conditions where U is conservative (reduced sediments with low permeability), the U/Th method can provide good chronologies for lacustrine deposits.

Air sample collections over the western Pacific have continued since 1992 as a part of Center for Global Environmental Research, National Institute for Environmental Studies (CGER-NIES) global environmental monitoring program. The air samples collected on the Japan-Australia transect made it possible to trace the seasonal and secular 14CO2 variations, as well as an increasing trend of greenhouse gases over the western Pacific. A subset of CO2 samples from latitudes of 10–15°N and 23–28°S were chosen for accelerator mass spectrometry (AMS) 14C analysis using a NIES-TERRA AMS with a 0.3–0.4% precision. These 14CO2 records in maritime air show seasonal variations superimposed on normal exponential decreasing trends with a time constant of about 16 yr. The Δ14C values in the Northern Hemisphere are lower those in the Southern Hemisphere by 3–4 during 1994–2002. The Northern Hemisphere record shows relatively high seasonality (2.3 ± 1.5) as compared with the Southern Hemisphere (1.3 ± 1.2). The maximum values of seasonal cycles appear in late autumn and early winter in the Northern and Southern Hemispheres, respectively. Oscillations of 1–10 yr over the western Pacific are found to correlate possibly with the El Niño/Southern Oscillation (ENSO) events.

The laboratory renewed operations in January, 1968 after a year's inactivity due to the absence of the head, who was on leave at the University of Bonn. Synthesized benzene continues as the dating medium, but various improvements have been made on the chemical method in order to increase capacity. Combustions are no longer carried out for normal materials. Instead, charcoal samples are used directly (after the usual pretreatment) and wood, plants, cloth, etc. are carbonized in a nitrogen atmosphere. Charring is a considerably more rapid procedure than combustion since it eliminates the CO2 collection, carbonate precipitation, and filtration steps. The charcoal then is reacted with molten lithium metal. Also, it was found that carbonates are attacked directly by hot lithium to produce carbides and the preliminary generation of CO2 gas is not indispensable. The carbide, cooled to room temperature, is reacted with old water (IVIC-317, Radiocarbon, 1967, v. 9, p. 240), the acetylene separated from hydrogen in a double liquid nitrogen-cooled trap, and benzene produced with a chromium activated silica-alumina catalyst.

Collagen-based pretreatment methods for bone yield inconsistent results for those samples where protein preservation is low, as frequently found in bones from the semi-arid zones of Australia and North America. New methods for dealing with low collagen bones are needed, and this paper suggests that the non-collagenous proteins, particularly the blood proteins, may offer advantages for AMS dating because of their better preservation. Amino-acid profiles of collagen and non-collagenous proteins suggest that such differential preservation may be due to physico-chemical differences, and help to explain the poor results from dating low-collagen bones.

Conventional radiocarbon calculations correct for isotopic fractionation using an assumed value of 2.0 for the fractionation of 14C relative to 13C. In other words, isotopic discrimination in physical and chemical processes is assumed to cause relative shifts in 14C/12C ratios that are exactly double those of 13C/12C. This paper analyzes a 1984 experiment that produced a value for the fractionation ratio in photosynthesis of 2.3, which is used to this day by some researchers in the fields of hydrology and speleothem geochemistry. While the value of 2.3 is almost certainly incorrect, theoretical work suggests that the true value may indeed deviate from 2.0, which would have significant implications for 14C calculations.

This list contains the results of measurements made during 1967 and 1968. Samples are counted in the form of acetylene gas, as previously, and ages computed on the basis of the Libby half-life, 5568 ± 30 yr. The error listed, always larger than the one-sigma statistical counting error commonly used, takes into account variable laboratory factors, but does not include external (field or atmospheric) variations.

The Varna I cemetery, on the Bulgarian Black Sea coast, is one of the most remarkable sites in European prehistory, with the world’s earliest large-scale assemblage of gold artifacts. Modeling of the first series of 14 accelerator mass spectrometry (AMS) dates yielded a duration of occupation at the site of ca. 150 years, ~4600–4450 cal BC. However, there were insufficient paired human–animal dates for a full consideration of the question of the marine reservoir effect. Here, a fuller set of 71 dates from 53 graves is presented. We identify a small reservoir effect in a number of individuals based on 14C, as well as carbon and nitrogen stable isotopes. We test the effect of this by building a series of different Bayesian models. Our favored model, including a correction for some of the human determinations, shows activity at the cemetery starting at 4596–4516 cal BC and ending 4427–4341 cal BC (at 95.4% probability). The overall span of activity covers ~120–260 years (93.6% prob.). The modeling shows that Varna I falls toward the beginning of the Bulgarian Late Copper Age.

13C and 14C were measured in the upper Jordan River, in its tributaries which issue from the Mount Hermon aquifer, and in the local atmospheric CO2 to evaluate the degree to which changes in the atmospheric 14C levels influence the 14C levels in the aquifer and in the Jordan River. The exchange fraction of CO2 between the river and the atmosphere was calculated for fall 1983 with the two carbon isotopes and it is shown that the value obtained with 14C (0.364) is the more reliable. The ratio of 14C in the Jordan River to that in the atmosphere in 1972 is similar to that in 1983, 0.66 and 0.67, respectively. This implies an approximately constant ratio (0.44) between the 14C level in the Mount Hermon aquifer base-flow and the 14C level in the atmospheric CO2. This information can be combined with the known historical fluctuations in the 14C levels of the atmosphere to calculate the 14C fluctuations in the discharge of the Jordan River into Lake Kinneret, backwards in time.

The Chauvet-Pont d'Arc Cave is one of the most important sites for the study of the earliest manifestations and development of prehistoric art at the beginning of the Upper Paleolithic. Different dating techniques have been performed thus far (AMS 14C, U/Th TIMS, 36Cl dating) to model the chronological framework of this decorated cave. The cave yielded several large charcoal fragments, which enabled the opportunity for obtaining multiple dates; thus, a First Radiocarbon Intercomparison Program (FIP) was initiated in 2004 using three charcoal pieces. The FIP demonstrated that those cross-dated samples belonged to a time period associated with the first human occupation. One of the statistical interests of an intercomparison program is to reduce the uncertainty on the sample age; thus, to further assess the accuracy of the chronological framework, the Second Intercomparison Program (SIP) involving 10 international 14C laboratories was carried out on two pieces of charcoal found inside two hearth structures of the Galerie des Mégacéros. Each laboratory used its own pretreatment and AMS facilities. In total, 21 and 22 measurements were performed, respectively, which yielded consistent results averaging ∼32 ka BP. Two strategies have currently been developed to identify statistical outliers and to deal with them; both lead to quasi-identical calibrated combined densities. Finally, the new results were compared with those of the FIP, leading to the important conclusion that five different samples from at least three different hearth structures give really tightened temporal densities, associated with one short human occupation in the Galerie des Mégacéros.

Subfossil trees with their annual rings constitute the most accurate and precise archive to calibrate the radiocarbon (14C) method. The Holocene part of the IntCal curve is based on tree-ring chronologies, absolutely dated by dendrochronological matching. For the Northern Hemisphere, the absolute curve starts at 12,325 cal BP. For the early part of the Younger Dryas (YD) climatic event (≈ 12,850–11,650 cal BP), there are only a few floating dendrochronological sequences, mainly from Switzerland and France. We present new 14C results from subfossil trees (Pinus sylvestris L.) collected from the Barbiers site (southeast French Alps). The dendrochronological series covers 416 years, corresponding to the onset of the YD period. In order to date our sequence, we matched it with the 14C record based on kauri trees from New Zealand. The Barbiers data were first averaged at the same decadal resolution as the kauri record. Statistical comparison of the different averaging options and matching techniques enables dating the Barbiers sequence to 13,008–12,594 ±10 cal BP, which thus includes the boundary between the Allerød and YD events. The new Barbiers record allows to calculate the 14C inter-hemispheric gradient (14C-IHG) during the period overlapping the kauri sequence. For the optimal dating option, the mean 14C-IHG is 37 yr with a standard deviation (SD) of 21 yr based on 43 decadal estimations (−6‰ with SD of 2‰). The 14C-IHG record exhibits minimal values, down to zero, between 12,960–12,840 cal BP. Excluding these minima leads to an average 14C-IHG of 45 yr with a SD of 14 yr based on 33 decadal values, in agreement with observations for the last two millennia. The Barbiers record suggests a 14C-IHG increase between the end of the Allerød period (IHG of 37 yr with SD of 14 yr) and the early part of the YD (IHG of 48 yr with SD of 14 yr), which is compatible with previously reported drop of deep-water convection in the North-Atlantic and the associated increase in wind-driven upwelling in the Southern Ocean.

Installation of a Sharp CDL-14 Carbon-Dating Laboratory was completed at Ohio Wesleyan University in June, 1962. The unit includes a sample conversion system constructed by Radiochemistry, Incorporated for the conversion of carbonaceous samples to the counting gas, methane. Counting equipment consists of a modified Sharp Low Beta system with a 6kv power supply and dual printout registers which automatically blank the counting circuits for 0.1 min for each 100-min printout. The detector has a sensitive volume of 0.5 L and is housed in a shield consisting of 8 in. of lead, 1 in. of steel, and 1 in. of mercury. Anticoincidence is provided by a cylindrical 2-L detector containing 16 anodes and filled with petroleum-generated methane to a pressure of 96 cm Hg.

A suite of 6 bone gelatin accelerator mass spectrometry (AMS) radiocarbon dates for Rattus exulans Peale and associated beta decay 14C dates for Austrovenus stutchburyi shell are presented for 4 middens at Pauatahanui, Wellington, New Zealand. Mean calibrated age ranges of Rattus exulans (520–435 BP and 350–330 BP at 95% confidence level) and shell (465–375 BP at 95% confidence level) from the 4 midden sites overlap. The agreement between Rattus exulans bone gelatin dates and associated shell provides an inter-sample comparison of 14C dating using both gas counting (beta decay) and AMS dating techniques. We examine the adequacy of the standard gelatinization treatment for bone samples, which has been employed consistently at the laboratory since 1995.

For most of human history, funerary burial has been unusual. Archaeology shows a shift in funerary practices in postglacial hunter-gatherers, in parts of Europe during the Late Mesolithic. This is documented by the burial grounds in the Tagus and Sado valleys in the southwestern Iberian Peninsula, Portugal, where ca. 376 burials were excavated. This study presents a chronology for the burial activity in these sites and contextualizes the start and end activity phases within regional environmental changes and cultural developments. The dataset consists of 76 14C dates on human bone (19 new, 57 published) including new dates from contexts in Portugal outside these valleys. Bayesian chronological models were defined in OxCal, and protein carbon contributions of marine foods were estimated by the Bayesian mixing model FRUITS. The results indicate a broader timeframe for the Late Mesolithic in Portugal, than previously suggested, starting during a period of significant environmental changes, ca. 8500–8300 cal BP, and ending ca. 7000 cal BP. The burial activity decreased during the establishment of Neolithic farmers in southwestern Iberia from ca. 7450 cal BP, however, these burial grounds continued to be used by Mesolithic hunter-gatherers, showing that diverse social structures and worldviews coexisted for several generations.