We present prehistoric mercury accumulation rates in a dated sediment core from Lagoa da Pata, a remote lake in São Gabriel da Cachoeira, northern Amazon. The sediment samples were subdivided for mercury and radiocarbon analyses. A group of 18 samples have been prepared at ANU for 14C dating by accelerator mass spectrometry (AMS). The dating results show a good correlation with depth in the core, down to 41,500 BP. Three distinct sections are clearly identified in the core. They consist of upper and lower organic-rich layers, separated by an inorganic layer which represents a short period of rapid accumulation around 18 ka BP. The mercury accumulation rate is found to be larger in the upper layer (18 ka to present) than in the lower one (41 ka to 25 ka), by a factor of three. The larger accumulation rate of mercury is probably associated with warmer temperatures and a higher frequency of forest fires during the Holocene.

In 2018 Pearson et al. published a new sequence of annual radiocarbon (14C) data derived from oak (Quercus sp.) trees from Northern Ireland and bristlecone pine (Pinus longaeva) from North America across the period 1700–1500 BC. The study indicated that the more highly resolved shape of an annually based calibration dataset could improve the accuracy of 14C calibration during this period. This finding had implications for the controversial dating of the eruption of Thera in the Eastern Mediterranean. To test for interlaboratory variation and improve the robustness of the annual dataset for calibration purposes, we have generated a replicate sequence from the same Irish oaks at ETH Zürich. These data are compatible with the Irish oak 14C dataset previously produced at the University of Arizona and are used (along with additional data) to examine inter-tree and interlaboratory variation in multiyear annual 14C time-series. The results raise questions about regional 14C offsets at different scales and demonstrate the potential of annually resolved 14C for refining subdecadal and larger scale features for calibration, solar reconstruction, and multiproxy synchronization.

In this paper, we investigate how to achieve high-accuracy radiocarbon measurements by accelerator mass spectrometry (AMS) and present measurement series (performed on archived CO2) of 14CO2 between 1985 and 1991 for Point Barrow (Alaska) and the South Pole. We report in detail the measurement plan, the error sources, and the calibration scheme that enabled us to reach a combined uncertainty of better than ±3%. The δ13C correction and a suggestion for a span (or 2-point) calibration for the 14C scale are discussed in detail. In addition, we report new, accurate values for the calibration and reference materials Ox2 and IAEA-C6 with respect to Oxl. The atmospheric 14CO2 records (1985–1991) are presented as well and are compared with other existing records for that period. The Point Barrow record agrees very well with the existing Fruholmen (northern Norway) record from the same latitude. The South Pole record shows a small seasonal cycle but with an extreme phase with a maximum on January 1st (±13 days). Together with its generally elevated 14C level compared to the Neumayer record (coastal Antarctica), this makes our South Pole data set a valuable additional source of information for global carbon cycle modeling using 14CO2 as a constraint.

The paper presents a comparison of U-series and radiocarbon dates of speleothems collected in several caves in central and southern Europe and southeast Africa. Despite a large spread of dates, mainly due to contamination with younger carbon, the group of corresponding 14C and 230Th/U ages of speleothem samples seems to be coherent with the previous suggestion of large deviation between the 14C and the absolute time scale between 35 and 45 ka BP. This agrees with the result of frequency analysis of published 14C and 230Th/U ages of speleothem.

Twelve new sites on Kaua‘i provide an island-wide view of late Quaternary (near time) environments on the oldest of the major Hawaiian Islands. Radiocarbon-dated lithologies are compared for estuarine sites on windward and leeward coasts, interior peat bogs ranging from 169 to 1220 m in elevation, prehistoric fishponds, and a sinkhole paleolake in the Maha‘ulepu cave system. Terrestrial sedimentation begins in many coastal sites about 6000 cal BP, as sea level approached modern levels. Prehuman sedimentation rates were quite low in all these sites, generally <2 mm/yr, although coastal sites in the late Holocene were subject to major episodic sediment influx from extreme events, including tsunamis, hurricanes, and floods. Interior sites are generally older, having accumulated humic clay and peat layers at least since the late Pleistocene. Since the arrival of humans less than two millennia ago, sedimentation rates have increased in some coastal sites, and further local increases (as much as two orders of magnitude) have occurred since European arrival. Evidence from sites containing fossils of extinct terrestrial snails is consistent with the hypothesis that human-caused extinctions have proceeded in three phases, corresponding to losses (generally the largest species) occurring soon after the arrival of the first humans, followed by a second wave of extinction in late prehistoric times, and a third after European colonization. Dating of sediments from fishponds constructed or enhanced by prehistoric Polynesians suggests that this early form of aquaculture was initiated on Kaua‘i by about 830 ± 50 BP. The most elaborate example of fishpond construction in the Hawaiian Islands, the Alekoko or Menehune fishpond on Kaua‘i's southeast coast, was probably undertaken by 580 ± 30 BP.

The following list includes samples from sites or sections described in archaeologic or geologic publications. Several others, already dated, will be published when the archaeologic and geologic investigations are concluded.

In 2003, a National Electrostatics Corporation (NEC) 5MV tandem accelerator mass spectrometer was installed at SUERC, providing the radiocarbon laboratory with 14C measurements to 4–5‰ repeatability. In 2007, a 250kV single-stage accelerator mass spectrometer (SSAMS) was added to provide additional 14C capability and is now the preferred system for 14C analysis. Changes to the technology and to our operations are evident in our copious quality assurance data: typically, we now use the 134-position MC-SNICS source, which is filled to capacity. Measurement of standards shows that spectrometer running without the complication of on-line δ13C evaluation is a good operational compromise. Currently, 3‰ 14C/13C measurements are routinely achieved for samples up to nearly 3 half-lives old by consistent sample preparation and an automated data acquisition algorithm with sample random access for measurement repeats. Background and known-age standard data are presented for the period 2003–2008 for the 5MV system and 2007–2008 for the SSAMS, to demonstrate the improvements in data quality.

The Tellervo dendrochronological software builds upon the Tree-Ring Data Standard (TRiDaS) to provide a tool for recording and managing all manner of dendrochronological data. However, Tellervo is especially useful for dendroarchaeological research. The traditional file formats used in dendrochronology—and by association the applications that use them—have very limited and nonstandard methods for recording rich information about dendro samples and their context. Such information is especially important in dendroarchaeological research to ensure accurate conclusions are made. Tellervo is described here in the context of research carried out as part of the excavations of the Theodosian Harbor at Yenikapı, Istanbul.

An interlaboratory comparison experiment for 14C measurements has been organized jointly by the Harwell and British Museum laboratories to include the working radiocarbon laboratories of the United Kingdom. The experiment has been run along the lines of that organized by the IAEA for tritium and has explored the problems of sample preparation, verification of equivalent levels, and presentation of results. Samples of benzene representing 5 age equivalent levels between twice modern and 20,000 years old have been prepared and distributed for measurement either by direct counting (liquid scintillation) or full process tests. Preliminary results received show excellent agreement both between laboratories and in comparison with the known relative activities of the prepared solutions. The possibility of extending the experiment to cover different sample types and a wider distribution of testing laboratories is briefly discussed.

Most of the 14C measurements reported here were made between October 1980 and October 1981. Equipment, measurement, and treatment of samples are as reported previously (R, 1968, v 10, p 36–37; 1976, v 18, p 290; 1980, v 22, p 1045).

Dates in this list have been determined at U. S. Geological Survey radiocarbon laboratory, Washington, since our 1960 date list (USGS V). Procedures for the preparation of acetylene gas used in the counting, and the method of counting, (two days in two separate counters) remain unchanged. However, the modern standard used is no longer wood grown in the 19th century, but 95% of the activity of NBS oxalic-acid radiocarbon standard, as recommended at the 1959 Groningen Radiocarbon Conference. Measurement of the oxalic-acid standard at our laboratory indicates 6.2 ± 1% more C14 activity than our modern wood standard; so use of the new standard should make no appreciable difference when comparing samples computed by the old method. W. F. Libby's (1955) half-life average for C14, 5568 ± 30 years, was used for the decay equation.

Despite many recent attempts to settle the dispute concerning the absolute date of the Minoan Santorini eruption, there are still differences between some archaeologists and scientists on the absolute dates and the reliability of radiocarbon dating. The recent publication of over 200 new 14C dates for dynastic Egypt rules out a major flaw in the historical chronology of Egypt and proves the reliability of 14C dating in the Nile Valley. Therefore, the student of Aegean archaeology and eastern Mediterranean interconnections is still confronted with an archaeologically based conventional, or “low,” chronology and a 14C-backed “high” chronology. New 14C determinations from different sites of the Aegean support the high chronology for the Late Minoan (LM) IA, while recent re-evaluation of LM IB determinations are slightly higher but more or less in agreement with archaeological estimations. The present contribution reviews archaeological and scientific data for the LM IA period and argues that a reduced (∼30 to 50 yr) offset between archaeological and 14C dates for the Minoan Santorini eruption may be possible, thus offering new perspectives for potential solutions for this problem.

This article presents a set of Late Pleistocene marine mollusk radiocarbon (AMS) age estimates of 30–50 14C kyr BP, whereas a MIS5 age (>75 ka) is indicated by quartz and feldspar OSL dating, biostratigraphy, U-Th dating, and age-depth relationships with sea level. These results indicate that the 14C dates represent minimum ages. The age discrepancy suggests that the shells are contaminated by younger carbon following shell death. The enigmatic 14C dates cannot be “solved” by removing part of the shell by stepwise dissolution. SEM analysis of the Late Pleistocene shells within a context of geologically younger (recent/modern, Holocene) and older (Pliocene) shells shows the presence of considerable amounts of an intracrystalline secondary carbonate precipitate. The presence of this precipitate is not visible using XRD since it is of the same (aragonitic) polymorph as the original shell carbonate. The combination of nanospherulitic-shaped carbonate crystals, typical cavities, and the presence of fatty acids leads to the conclusion that the secondary carbonate, and hence the addition of younger carbon, has a bacterial origin. As shell material was studied, this study recommends an assessment of possible bacterial imprints in other materials like bone collagen as well.

The loessic deposits along with their palaeosols of the Kashmir Valley have been 14C dated using both organic and carbonate fractions. The 14C dates on both the fractions show good concordance. The 14C dates indicate that the last deglaciation in Kashmir (34° N) already started CA 18,000 ± 1000 BP at CA 1600m and CA 15,000 BP at CA 3000m altitude and thus support the recent global evidence of deglaciation having started several millennia before the Holocene.

Dating of the amino acid hydroxyproline from bone collagen has been shown to produce accurate and reliable radiocarbon dates. This article presents further application of the method demonstrating it can be used to obtain dates for both low-collagen and contaminated bones, extending the capability of 14C dating archaeological bone from conventional limits imposed by alternative pretreatment methods. The method therefore has the potential for significantly benefiting the accelerator mass spectrometry (AMS) dating community in the 14C dating of archaeological bone.

We discuss the significance of 32 radiocarbon dates from the archaeological sites of Tel Beth Shean and Tel Rehov in northern Israel. All dates are from Iron Age I and II archaeological contexts (12th–8th centuries BCE). Most of the dates were done on short-lived samples (seeds and olive pits), while some are on charred timber. The samples are organized in several homogeneous clusters according to their context. This series is one of the largest groups of 14C dates from the Iron Age in the Levant. The paper discusses the correlation between the 14C dates and the traditional archaeological dates of the same context. Results from two laboratories and two calibration curves are compared, showing some significant differences in one case. We conclude with an evaluation of the relevance of 14C dating for the current debate about the chronology of the Iron Age in Israel, and in historical periods in general.

Unleached aliquots of TIRI/FIRI turbidite were analyzed by accelerator mass spectronomy (AMS) over a timespan of 18 months. Individual analyses ranged from 18,090–18,245 yr BP with reported errors between 30–50 yr. The weighted average fraction modern (FM) of these 28 measurements is 0.10378 ± 0.00008 (which equates to 18,199 ± 8 yr BP) and the measurements show a 1 standard deviation scatter of 0.00044 (±35 yr). The fractional error of these results indicates reproducibility of individual measurements at the 4 (1σ) level, which is consistent with the quoted counting-statistics-based errors. Laboratories engaged in the determination of 14C results at reasonably high precision should consider taking advantage of the TIRI and FIRI sample materials in the role of process standards. Additional suites of high-precision data are necessary to refine the accuracy of these sample materials.

This paper deals with the potentialities and technical and methodological issues associated with the use of lumps of not completely melted lime as material suitable for the radiocarbon dating of aerial lime mortars and plasters. In fact, the identification and selection of single aggregates of unmelted lumps allows one to reduce the possible contamination resulting from external sources of carbon such as “14C-dead” limestone in sand added to the mixture during preparation. This procedure results in the possibility for accurate 14C determinations from single pieces of masonry, supplying important information about the construction phases of historical buildings. The potential of this approach is shown by presenting the results of the archaeological study on the walls of San Nicolò of Capodimonte church (Camogli, Genoa, Italy), where this technique has been successfully applied to obtain absolute ages of different parts of the building. The obtained results were then compared with the information gathered from historical sources and with stratigraphic and other archaeological studies.

The following list covers the samples measured at the Uppsala radiocarbon laboratory during 1959.

The presented research involves the analysis and radiocarbon dating of 2 different groups of carbonate mortars, from Kraków, Poland and Hippos, Israel. Differences in composition of the mortars are reflected in different rates of their acid leaching. The Israeli mortars contain carbonate-basaltic aggregates, which may cause overestimation of 14C age. Preliminary processing of these samples (choice of selected grain-size fraction and collection of CO2 released during the first phase of the acid-leaching reaction), enabled us to obtain good agreement between the 14C dates and the age derived from historical contexts. A similar method of preliminary processing was applied to the carbonate mortars of the Medieval building in Kraków. The Polish samples represent carbonate mortars with some admixture of quartz aggregates, suggesting that they would be an ideal material for 14C dating. However, these samples contained white lumps of carbonates, the structure of which differed from that of the binder. These admixtures, possibly related to the hydrological conditions at the site and to the character of the ingredients, appeared modern, and if not removed prior to acid leaching, they could cause underestimation of the age of samples. The 14C dates of the mortars from the walls of the Small Scales building in Kraków are the first obtained for this object, and their sequence does not contradict archaeological indications on several phases of the building construction.