The interpretation of 14C histograms is complicated by the non-linearity of the 14C time scale in terms of calendar years, which may result in clustering of 14C ages in certain time intervals unrelated to the (geologic or archaeologic) phenomenon of interest. One can calibrate 14C histograms for such distortions using two basic approaches. The KORHIS method constructs a 14C histogram before calibration is performed by means of a correction factor. We present the CALHIS method based on the Groningen calibration program for individual 14C ages. CALHIS first calibrates single 14C ages and then sums the resulting calibration distributions, thus yielding a calibrated 14C histogram. The individual calibration distributions are normalized to a standard Gaussian distribution before superposition, thus allowing direct comparison among various 14C histograms. Several experiments with test data sets demonstrate that CALHIS produces significantly better results than KORHIS. Although some problems remain (part of the distortions due to 14C variations cannot be eliminated), we show that CALHIS offers good prospects for using 14C histograms, particularly with highly precise and accurate 14C ages.

We show that smoothed versions of the high-resolution calibration curve should be used when 14C ages are calibrated with large (> ∼30 14C yr) measurement errors (represented by standard deviation δm) or are mixtures of elements of variable age (natural sample error with standard deviation δn). The degree of smoothing should agree with the standard deviation of total sample error, δt, the square root of the quadratic sum of δm and δn. However, in most cases, δt is not well known, especially due to difficulties in quantifying δn. We present an inverse method that gives a measure of mean δt, for different materials that are widely used in (conventional) 14C dating. Calculations with large (>100) data sets of wood, charcoal, ombrotrophic peat and minerotrophic peat/gyttja samples indicate that δt of such materials is generally much larger than previously assumed, mainly because of large values of δn. This means that particularly in organic deposits, strongly smoothed calibration curves should be used where medium-term 14C variations (wiggles) are completely straightened. This has especially major consequences for calibrating 14C histograms for natural 14C variations. We conclude that 14C histograms consisting of samples of organic deposits do not require correction for medium-term 14C variations and that uncalibrated 14C histograms need not be as suspect as is usually believed.

Measurements of the stable isotope ratio 13C/12C, relative to PDB, were made for fractionation correction purposes on all oak samples used in the Irish oak 14C calibration curve. Stable isotope data have not been published previously. We have collated the stable isotope data from the calibration work, carried out some further measurements to investigate anomalies in the original results, and generated tables of data that include site and tree information pertaining to both stable isotopes and source material for 14C calibration measurements. The data suggest that land-grown trees tend to be isotopically lighter than bog-grown wood, and that the Irish trees used in the calibration exercise tend to be isotopically heavier than those from Scotland and England. Preliminary analysis of the data is given.

Loess deposition within the Loess Plateau of China records the history of environmental change over the last 2.5 Myr. Loess-paleosol sequences of the last 10 ka, which have preserved information of global climate change, relate closely to human occupation of the area. Hence, studies of the deposition and development of Holocene loess are significant for studying environmental change and problems associated with engineering geology. We present here stratigraphic relations among four profiles from the south, west and center of the Loess Plateau. On the basis of 14C radiometric and AMS dates of organic material extracted from the paleosols, together with magnetic susceptibility measurements down each profile, we discuss Holocene stratigraphic divisions within the Loess Plateau, and suggest that the Holocene optimum, characterized by paleosol complexes, occurred between 10 and 5 ka bp. From 5 ka BP to the present, neoglacial activity is characterized by recently deposited loess.

The Xi'an Laboratory of Loess and Quaternary Geology has developed a small sample 14C dating facility consisting of a Wallac 1220 Quantulus™ liquid scintillation spectrometer, and a miniature benzene synthesis line based on the synthesis procedures used at the Australian National University (ANU). This line can produce ca. 0.3-ml benzene samples, which are then measured for 14C activity using 0.3-ml Teflon vials developed by Wallac Oy. The counting performance of the Quantulus™ spectrometer using 0.3-ml vials has been evaluated, and a potential age limit of ca. 45,000 BP has been obtained for samples containing up to 250 mg carbon. This dating facility fills the gap between large sample (2.4–6 g carbon) and microsample (<1 mg carbon) handling to form a 14C dating method sequence.

The conventional 14C ages of 8 marine shells of known age and 11 marine shells stratigraphically associated with dated wood charcoal show considerable variation from expected ages. One source of this variation is seashore geology; comparison of 6 AMS dates on 3 species of shallow-water, herbivorous gastropod shells from Pleistocene limestone and Holocene volcanic coasts shows that shells from Pleistocene limestone coasts can have apparent, or reservoir, 14C ages up to 620 yr greater than shells of the same species from volcanic coasts. The relatively great variation in apparent ages of Hawaiian marine shells poses problems for their use in dating archaeological sites. For best results, an archaeological marine shell should be sourced to a particular local environment, and the apparent age of shells in that environment determined by dating well-provenienced shells of known age.

Twenty-seven 14C determinations from Aitutaki, southern Cook Islands inform on human settlement and Holocene coastal processes. I examine sedimentary, radiometric and archaeological data from Aitutaki with reference to regional evidence for a minor Holocene sea-level regression, which are in general agreement. Related processes of shoreline progradation and aggradation created near-shore environments conducive to human habitation, directly evidenced by ca. AD 900–1200. Nevertheless, biotic materials associated with this early cultural stratum suggest human colonization prior to this time. Archaeological preservation and recovery also may have been affected by changing sea level and related sedimentary processes.

Lakes Barrine and Eacham and their small, discrete, forested catchments are sites of intensive sedimentological, palynological and ecological research. The studies that we present here concentrate on integrating population statistics of tree species of the living forest with their histories, as documented by fine-resolution pollen analysis (Green and Dolman 1988). Most of the work has been undertaken at Lake Barrine, where the last 5 ka is recorded in laminated sediments. Additional information about these sites and about aspects of the project is contained in Chen (1986, 1987, 1988), Goodfield (1988), Grindrod (1979), Timms (1976, 1979) and Walker (1988).

The following list consists of dates for archaeological samples measured mostly between October 1989 and November 1990. Charcoal and grain samples were pretreated with 1M HC1 followed by washing in water and, in the majority of cases, with dilute alkali for the removal of humic acids. Wood samples were treated in the same way, or, if large enough, reduced to cellulose with chlorine dioxide produced in situ. Antler and bone samples were treated with cold dilute acid. We use the term “collagen” to mean the acid-insoluble organic fraction produced by this treatment rather than the true biochemical definition.

This list consists of radiocarbon dates for geological samples measured from 1988 to 1990 at the resumed National Taiwan University (NTU) Radiocarbon Dating Laboratory. The NTU Radiocarbon Dating Laboratory was re-activated in 1988, after more than 14 years.

This paper includes 14C measurements of geological and environmental samples processed by liquid scintillation counting of benzene between 1991 and the end of 1992. All samples, from central and northern Italy and from the Gulf of Venice, Adriatic Sea, relate to scientific projects conducted in collaboration with colleagues from both Italian universities and National Council of Research (CNR) institutions.

This is a partial list of archaeological samples processed between May 1990 and December 1992 at the Department of Earth Sciences Radiocarbon Dating Laboratory of the University of Rome. Most of the samples in the list, both from Italy and other countries, were related to excavations carried out by researchers at the University of Rome, Department of Scienze dell'Antichità. Although primarily measured for archaeological studies, some of these dates also have geological and paleoenvironmental relevance.

This date list reports dates of archaeological samples of Mesolithic and Neolithic sites of Estonia, Latvia and Lithuania. We use liquid scintillation counting at the Geochemical and Statistical Laboratory of the Institute of Zoology and Botany, Estonian Academy of Sciences. Our modern standard is benzene enriched in 14C and its activity is checked with an NBS oxalic acid standard sample. Dates are given in conventional 14C years, based on the Libby half-life of 5570 ± 30 yr. AD 1950 is the reference year. Errors are based on one standard deviation calculated from count rates.