The Obi-Rakhmat Grotto is one of the key Paleolithic sites in Central Asia. Archaeological excavations have revealed 22 strata containing archaeological materials. Lithic assemblages from all cultural layers display features similar to both late Middle Paleolithic blade industries and early Upper Paleolithic complexes in Southwest Asia and the Siberian Altai Mountains; this suggests a gradual Middle-to-Upper Paleolithic transition occurred in western Central Asia. Hominid remains found at Obi-Rakhmat (layer 16) show a mixture of archaic and modern traits. Different chronometric methods (radiocarbon, optically stimulated luminescence [OSL], U-series, and electron spin resonance [ESR]) were applied to the site's deposits. It appears that 14C dates are more reliable in terms of correspondence to the general framework of the Paleolithic of Central Asia and neighboring regions, and after critical analysis and the deletion of outliers, the upper part of the site's cultural sequence can be dated between 36,000–41,400 BP (layer 7) and ∼48,800 BP (layer 14.1). The U-series dating results are less secure due to the high uranium content and the presence of detritus, which contaminates dated sediments (travertine). The OSL dating gave uniform ages for all cultural succession (∼8 m of deposits), and confirms a very rapid sedimentation rate. Results of ESR dating depend greatly on the choice of uptake model. Dates calculated for the early uptake to some extent correspond to 14C data. The linear uptake chosen by Skinner et al. (2007) makes sediments very old (about 55,000–90,000 yr ago), which contradicts 14C dates and does not correspond well to the regional archaeological context.

Recent experimental work has suggested that the relative fractionation of 14C to 13C may differ from the accepted value of b = 2. In order to explore the implications of this possibility, the standard formulae for correcting radiocarbon dates for fractionation effects are rederived, but without making any of the usual assumptions or approximations. A generalized dating equation is derived (where ASN and AON are normalized sample and standard activities, β is a factor which reflects changes in atmospheric 13C and 14C content, {RST (o)/RST}b accounts for post-depositional changes in sample 13C ratio, and tcal is calendar age in years before ad 1950. The errors in calculated ages which might arise from different b values are estimated and shown to be small relative to other dating uncertainties. The effect of b ≠ 2 may be important in the calibration of radiocarbon dates using tree-ring samples of known age. A theoretical analysis suggests that b ≠ 2 effects may result in a correlation between age anomaly (ie, the difference between radiocarbon age and calendar age) and sample 13C data. However, an analysis of published data reveals no meaningful correlation. This result, while not eliminating the possibility that b ≠ 2, highlights its unimportance even in this high-precision application of radiocarbon dating.

Measurements have continued with the 6 L counter. A counter of similar design but with 1 L volume has recently been brought into operation. Despite replacement of the teflon parts, the 1.5 L Oeschger-type counter has not worked consistently and has not been used for dating. Results are not corrected for δ C13. Errors quoted refer only to the standard deviation calculated from a statistical analysis of count rates and the Libby half-life of 5570 ± 30 yr.

Alkali pretreatment is used for all samples of charcoal, peat, wood, and plant material provided they are of sufficient quantity. It is now standard practice to boil the sample in 5% HCl solution and filter, both before and after boiling it in 2% NaOH solution. Between each treatment it is washed in boiling distilled water and is finally oven dried at 110°C. Concentrations of acid and alkalis are varied to suit each sample but the sequence of the pretreatment is always the same. In some cases a humate extract is obtained by precipitation with weak acid from the alkali solution filtrate.

The collagen fraction is obtained from samples of bone using the method of Krueger (1966) by treatment with dilute acid under reduced pressure. The gas evolved during the treatment is usually discarded but is occasionally retained and dated as the mineral fraction.

After mechanical cleaning, samples of shell are dissolved in stages with 6N HCl to divide them into two or three fractions corresponding to the outer, middle, and inner layers of the shell. Normally the outer fraction is discarded when three fractions have been prepared.

The following list presents dates obtained on a fraction of the total number of measurements made during the years 1961 and 1962 and measurements made previously for which sample data has been recently received. The results which do not appear are withheld pending additional information, or at the request of our clients.

The following list includes many of the measurements made since publication of Yale VI, but many are withheld pending receipt of more complete information or additional samples. We report dates in terms of the Libby half life of C14, 5570 ± 30 yr; geochemical measurements, when normalized for C13 content, are given as δ in parts per mil, as described in Yale VI. As before, we acknowledge the technical assistance of George Young, Jonathan King, Sheldon Nankin, and now Carolyn Haupt who has also joined our staff. Our work has been supported by the National Science Foundation, under grants G-19080 to Stuiver and G-19335 to Deevey, and by the U. S. Atomic Energy Commission under contract AT (30–1)–2652.

Radiocarbon offers a unique possibility for unambiguous source apportionment of carbonaceous particles due to a direct distinction of non-fossil and fossil carbon. In this work, particulate matter of different size fractions was collected at 4 sites in Switzerland to examine whether fine and coarse carbonaceous particles exhibit different fossil and contemporary sources. Elemental carbon (EC) and organic carbon (OC) as well as water-soluble OC (WSOC) and water-insoluble OC (WINSOC) were separated and determined for subsequent 14C measurement. In general, both fossil and non-fossil fractions in OC and EC were found more abundant in the fine than in the coarse mode. However, a substantial fraction (∼20 ± 5%) of fossil EC was found in coarse particles, which could be attributed to traffic-induced non-exhaust emissions. The contribution of biomass burning to coarse-mode EC in winter was relatively high, which is likely associated to the coating of EC with organic and/or inorganic substances emitted from intensive wood burning. Further, fossil OC (i.e. from vehicle emissions) was found to be smaller than non-fossil OC due to the presence of primary biogenic OC and/or growing in size of wood-burning OC particles during aging processes. 14C content in WSOC indicated that the second organic carbon rather stems from non-fossil precursors for all samples. Interestingly, both fossil and non-fossil WINSOC concentrations were found to be higher in fine particles than in coarse particles in winter, which is likely due to primary wood burning emissions and/or secondary formation of WINSOC.

In this paper, we examine 3 different models used to estimate turnover of soil organic carbon (SOC) fractions using radiocarbon measurements: one conventional carbon dating model and two bomb 14C models. One of the bomb 14C models uses an atmospheric 14C record for the period 22,050 BC to AD 2003 and is solved by numerical methods, while the other assumes a constant 14C content of the atmosphere and is solved analytically. The estimates of SOC turnover obtained by the conventional 14C dating model differed substantially from those obtained by the bomb 14C models, which we attribute to the simplifying assumption of the conventional 14C model that the whole SOC fraction is of the same age. The assumptions underlying the bomb 14C models are more applicable to SOC fractions; therefore, the calculated turnover times are considered to be more reliable. We used Monte Carlo simulations to estimate the uncertainties of the turnover times calculated with the numerically solved 14C model, accounting not only for measurement errors but also for uncertainties introduced from assumptions of constant input and uncertainties in the 14C content of the CO2 assimilated by plants. The resulting uncertainties depend on systematic deviations in the atmospheric 14C record for SOC fractions with a fast turnover. Therefore, the use of the bomb 14C models can be problematic when SOC fractions with a fast turnover are analyzed, whereas the relative uncertainty of the turnover estimates turned out to be smaller than 30% when the turnover time of the SOC fractions analyzed was longer than 30 yr, and smaller than 15% when the turnover time was longer than 100 yr.

The characterization of late Holocene climates in northern Australia has, in the past, been based on local investigations. This examination of the chenier record of northern Australia indicates that there has been a statistically significant regional change in conditions between 1600–2800 years bp, possibly a period of relative aridity. Support for this conclusion may be found in the vegetation record from the Atherton Tableland where numerical comparisons of dryland fossil and modern pollen spectra suggest that rainfall may have been up to 50% higher during the period 7000 to 3000 bp.

Paired radiocarbon and 230Th/U dating was performed on 13 surface corals from submerged reefs in the Marquesas and from raised terraces in Vanuatu. The absolute ages of the corals analyzed ranged from 3000 to 15,000 cal yr. Estimates of the difference between the absolute and 14C ages of these corals are in agreement with previous determinations up until 11,500 cal yr. The resulting mean sea surface reservoir age R is determined at 390 ± 60 yr for the Marquesas region (9°S), which is slightly higher than the R value at 280 ± 50 yr for the Tahiti Islands (18°S). Multiple 14C analyses of 2 corals from the Marquesas present scattered 14C ages at ~12,000 and ~15,100 cal yr. This could be attributed to rapid changes of the 14C content of surface waters around the Marquesas Islands or to a subtle submarine diagenesis.

A first list of datings by our laboratory was published in 1957 (Bella and Cortesi, 1957). The measurements were performed with a solid Carbon counter (Ballario et al., 1955). Between the beginning of 1958 and December 1961 laboratory apparatus was completely renewed and proportional gas-counters were introduced. At present four counters are available. Measurements are carried out with CO2 at 3 atm pressure.

Principles contributing to changes and the final balance of rejuvenation in 14C dates of soil profiles are identified. The annual addition to the atmosphere of ca 5.5·1012kg of dead carbon from fossil carbon sources and 1.5·1012kg of older carbon from forest clearing make soil appear older. Bomb carbon and annual recycling of most of the 115·1012kg of terrestrial organic carbon, equivalent to the annual photosynthetic turnover of carbon, rejuvenates soil dates. This also applies to root growth, animal transport, and in acid or alkaline soils, to humus percolation. All available 14C dates of soil profiles were evaluated for the impact of bomb carbon. We also studied the effects of morphogenetic soil-forming processes, such as turbations, on soil rejuvenation. Bioturbation, as a general principle of soil dynamics, requires more differential treatment due to modern and bomb carbon that constitutes body carbon of earthworms as well as steadily increasing 14C age with depth in all Mollisols.

Freshwater reservoir effects (FRE) can cause problems when radiocarbon dating human skeletal material from the Eurasian steppe. This article presents the first results of research into the extent of the FRE in the sites of Borly 4 (Eneolithic) and Shauke 1 and 8b (Early Bronze Age), northeastern Kazakhstan. Accelerator mass spectrometry (AMS) 14C dating and stable isotope (δ13C, δ15N) analysis of associated groups of samples (32 samples, 11 groups in total) demonstrate the following: (a) the diet of the humans and fauna analyzed was based on the C3 foodchain with no evidence of a C4 plant (such as millet) contribution; aquatic resources apparently were a continuous dietary feature for the humans; (b) the first 14C dates obtained for the Upper and Middle Irtysh River region attribute the Eneolithic period of the area to the 34th to 30th centuries BC, and the Early Bronze Age to the 25th to 20th centuries BC, with a ~450-yr hiatus between the two periods; (c) the maximum fish-herbivore freshwater reservoir offset observed equals 301 ± 47 14C yr. As such, 14C dates from aquatic and human samples from the area need to be interpreted with caution as they are likely to be affected by the offset (i.e. appear older). The article also discusses the effect of a sodium hydroxide (NaOH) wash on δ13C, δ15N, C:Natomic levels and collagen yields of the bone samples. Our results indicate a minor but significant effect of NaOH treatment only on C:Natomic ratios of the samples.

In liquid scintillation counting (LSC), small variations in benzene purity can cause 14C pulse-height spectra to move with respect to the counting window. Thus, one must carefully monitor the purity of each benzene sample and apply corrections for spectral shifts. I describe here the techniques used at Queen's University Belfast for deriving correction factors for observed small variations in benzene purity. I also describe the methods used at our laboratory to fine-tune our Quantulus LS counters for high-precision dating. The tuning of the instruments minimizes the effect of fluctuations in gain that may occur during the long counting periods required for high-precision dating. Any remaining influences on efficiency owing to gain changes are corrected for, along with the purity correction, by continuous monitoring of the spectrum produced by the external source.

The measurements reported were made during the 2nd half of 1967 in the Isotope Lab. of the Inst. of Geophysics and Planetary Physics as a continuation of the UCLA date lists I through VII. Samples were analyzed as CO2-gas at close to one atm in a 7.5 L proportional counter with 3 energy channels described earlier. Radiocarbon ages were calculated for uniformity on the basis of a 5568 yr half-life as was recommended by the Sixth International C14 and H3 Dating Conference, June 1965, in Pullman, Washington. The standard for the contemporary biosphere remains as 95% of the count rate of NBS oxalic acid for radiocarbon labs. Background determinations have been based on CO2 obtained from marble. The error listed is always at least a 1σ statistical counting error. In critical cases C13/C12 isotope ratio measurements were made to correct the dates for fractionation. All samples were subjected to accepted NaOH and/or HCl pretreatments depending on the individual case as a minimum to exclude contamination.

The Lagoon of Venice was formed about 6000 years ago due to the marine transgression associated with the late Pleistocene sea level rise. Already by the time of the Republic of Venice (727–1797 AD) it was recognized that the future of the city and its many historical buildings was strongly correlated with the future of the lagoon itself. During the centuries many engineering projects such as modification of the fluvial systems, construction of coastal barriers, and dredging of navigation channels were carried out to preserve the lagoonal environment. The present-day lagoon is the result of all these processes and covers an area of 540 km2 with an average depth of 0.6 m. A series of radiocarbon age determinations carried out on material obtained from cores collected in the Lagoon of Venice indicate within the sedimentary units the existence of a number of discontinuities and slumping events due to the highly active lagoonal environment. The evaluation of data obtained from a variety of different materials—both terrestrial and marine—allowed us to determine for the first time the marine reservoir effect in the lagoon of Venice. The discussion includes a comparison with other relevant measurements and a possible explanation to the relatively high reservoir age (1200–1300 yr).

The following list consists of dates for archaeologic and some geologic samples, mostly measured from January 1978 to December 1979. The dates were obtained by liquid scintillation counting of benzene using the laboratory procedures outlined in previous lists (see, eg, BM-VIII, R, 1976, v 18, p 16). The dates are expressed in radiocarbon years relative to ad 1950 based on the Libby half-life for 14C of 5570 yr, and are corrected for isotopic fractionation (δ13C values are relative to PDB). No corrections have been made for natural 14C variations. The modern reference standard is NBS oxalic acid (SRM 4990). Errors quoted with the dates are based on counting statistics alone and are equivalent to ± 1 standard deviation (± 1σ). Dates in this list reported to submitters or published elsewhere before the introduction of the new guidelines for rounding of computed figures have deliberately been left unrounded. From BM-XV onwards all BM dates will be rounded before publication in conformity with the recently recommended procedures (R, 1977, v 19, p 362). Descriptions, comments, and references to publications are based on information supplied by submitters.

In 1994, the Gliwice Radiocarbon Laboratory began operating a liquid scintillation spectrometry system, consisting of a Quantulus 1220™ spectrometer and two vacuum rigs for benzene production. This paper describes the procedures used for the benzene synthesis from samples containing < 1 g of carbon and in the range 1 to 10 g of carbon. We also present the Quantulus calibration procedures used in the Gliwice Radiocarbon Laboratory and NERC Radiocarbon Laboratory, and compare the calibration parameters.

This list reports measurements made at this laboratory since the preparation of the last list (Texas II). About twenty measurements are not reported because they are from series which are incomplete. Ages were calculated using a C14 half-life of 5568 yr and 1950 as the reference year. The modern standard used was 95% of NBS oxalic acid activity. The deviations reported are based on the counting statistics of the sample, background, and modern, and are ±1σ except that when the sample count approached either the modern standard or the background, 2σ limits are reported.

The importance of chronometric dating in archaeology cannot be overemphasized. Indeed, most chronologies developed throughout the world during the past three decades have depended on radiocarbon age determinations to provide a temporal framework for examining change over time in cultural sequences during the late Pleistocene and Holocene. With the advent of legislation in the mid-1960s designed to protect archaeological sites in the United States threatened by increased urban development or government sponsored projects, archaeological surveys and excavations were mandated as a means for preserving information otherwise destroyed. As a result, thousands of projects have contributed to a growing body of “gray literature,” ie, unpublished proprietary or manuscript reports with very limited circulation. Within these reports are hundreds, if not thousands, of 14C age determinations, most of which are not accessible in published form. One objective of this paper is to present all the 14C age determinations for the island of Moloka'i, Hawai'i as of December 1988, including 41 dates never before published with stratigraphic details.

Dietary offsets in radiocarbon dates are becoming increasingly interesting to researchers, not only because of their impact on the reliability of chronologies but also because of the possibilities for extracting further dietary information from the 14C data itself. This is the case with the cemeteries of the Cis-Baikal region being studied as part of the international Baikal-Hokkaido Archaeology Project set up to examine hunter-gatherer cultural dynamics in eastern Asia. Fortunately, to control for a freshwater reservoir offset, we were able to obtain a number of paired terrestrial herbivore and human material for 14C dating. This article tests the correspondence between stable isotope evidence and the offsets seen in 14C values and the implications for the analysis of the 14C measurements as “chronometric dates.” This is an unusually well-documented example of freshwater reservoir offsets, providing an ideal case study to test different approaches to analyzing such offset information. Here, a purely Bayesian approach is compared with the more frequently applied linear regression analysis.