For over 2 decades, there have been calls for Polynesian archaeologists to identify radiocarbon samples to taxon and material type, and preferentially date short-lived materials. This stems from recognition that even modest amounts of inbuilt age are problematic in this oceanic region where human settlement dates to the last 3 millennia or less. Despite programmatic statements to this effect, and empirical demonstrations of value, uptake of these practices has been slow. This article suggests that short-lived materials be defined as those with lifespans of 10 yr or less, recognizing that reducing the distance between target event and the dated material is an ongoing aim for archaeology. We identify both short-lived materials that are suitable for dating and long-lived species (>75 yr) that should be avoided given their potential for inbuilt age. Additionally, we suggest that given the destructive nature of 14C dating there is value to (1) obtain high-resolution photographs of samples prior to analysis, (2) split samples and archive residuals when possible, and (3) routinely report the tools and expertise used in identification. Past and recent dating analyses at a Polynesian site in the southern Cook Islands are used to illustrate how the suggested protocols might enhance current and future studies. We also establish that mature Calophyllum inophyllum, a common coastal tree and valued timber species, has been in the southern Cook Islands for at least the last 700 yr and is likely to be indigenous and long-lived.

A primary concern with dating skeletal material from oceanic environments is the effect of marine-derived carbon on resulting radiocarbon ages. Due to uncertainties in local marine reservoir effects and the proportion of marine carbon incorporated in bone, dates from archaeological skeletal material exhibiting marine dietary signatures have previously been characterized as problematic and removed from further analysis. While in certain instances this may be appropriate, in others it is not. This article presents 26 new 14C dates obtained from human teeth (dentin collagen) on Rapa Nui. The effect of the local marine reservoir on 14C ages is evaluated assuming a range of incorporated marine-derived carbon. The results indicate that the Rapa Nui 14C ages are not significantly different under varying realistic extreme ranges in estimates of the proportion of marine carbon consumed. The article argues that this is primarily due to the small local marine reservoir effect measured in Rapa Nui and relatively lower reliance on marine resources in the prehistoric and protohistoric population.

The Fijian archaeological record is segmented into a series of phases based on distinctive transformations in ceramic forms. Interpretations of the mid-sequence (∼1500–1300 cal BP) transition between the Fijian Plainware phase and the Navatu phase are contentious, with alternative explanations of population replacement versus internal processes of culture change. We present and analyze a series of Fijian Plainware and Navatu phase AMS radiocarbon dates acquired from superimposed but stratigraphically separated occupation floors at the Sigatoka Sand Dunes site on the southwest coast of Viti Levu. Employing an OxCal Bayesian sequential model, we seek to date the temporal span for each occupation as well as the interval of time occurring between occupation floors. The latter is estimated to be 0–43 calendar years at 2σ probability. The magnitude of ceramic and other differences between the Fijian Plainware and Navatu phase occupations at Sigatoka is substantive. We conclude that the abruptness of this change can be explained only by exogenous replacement at the Sigatoka site.

Fifteen accelerator mass spectrometry (AMS) radiocarbon dates obtained on small subsections of archaeological and historical Crassostrea virginica (eastern oyster) shells provide a means to test for intrashell variability in 14C content in late Holocene Chesapeake Bay mollusks. Although salinity and temperature vary considerably throughout the year, the Chesapeake Bay generally lacks the strong coastal upwelling present in the eastern Pacific where intrashell 14C variability is significant. Intrashell variability in Chesapeake Bay C. virginica is between ∼60–100 14C yr, considerably smaller than the 120–530 14C yr ranges noted for shells from strong upwelling zones. As a precaution, we follow Culleton et al. (2006) and argue that large subsamples of shells across multiple growth increments are ideal for AMS 14C dating of mollusks to offset potential issues of intrashell 14C variability.

This article reports temporal changes in the measured oceanic geochemical properties of the Arabian Sea and the equatorial Indian Ocean by reoccupying six stations investigated during the GEOSECS expedition in 1977 and 1978. Observed differences are interpreted in terms of plausible changes in the environment and climate that have occurred in response to natural or anthropogenic processes. The depth profiles of major parameters such as dissolved oxygen, ΣCO2, major nutrients (silicates, nitrates, and phosphates), and radiocarbon in dissolved inorganic carbon were measured during the cruises between 1994 and 1998 along with temperature and salinity. Most stations in the Arabian Sea show an increase in salinity by ∼0.2 to 0.3 salinity units in the top 400 m, whereas one station in the equatorial Indian Ocean showed a decrease in salinity by ∼0.1 units, indicating a likely change in the evaporation-precipitation (E-P) balance. The ΣCO2 increased by an average of 8 μM within the top 1200 m of the Arabian Sea. The depth profiles of nitrates and dissolved oxygen for the central Arabian Sea stations show significant variations, while only marginal changes are seen for silicates and phosphates relative to the GEOSECS data. The decrease in Δ14C of surface waters is due to the steady decrease in atmospheric 14C concentration since GEOSECS, and the Δ14C increase in subsurface waters is attributed to the downward vertical diffusion of bomb 14C interpreted in terms of atmosphere to ocean transfer and lateral advection of water masses.

Accelerator mass spectrometry (AMS) was introduced at Yamagata University in 2010, including the measurement of radiocarbon. In the Yamagata University laboratory (YU-AMS), the application of 14C AMS is aimed at microdose pharmacokinetics investigation and the development of improved sample preparation techniques. The lab also measures environmental samples. With the installation of this AMS system, a new automated sample production system was installed, which is composed of an elemental analyzer, a glass vacuum line, and an isotope ratio mass spectrometer (IRMS). In this system, it is also possible to measure stable isotopes (δ13C, δ15N, and δ34S) of the sample gas using a mass spectrometer. To increase the amount of CO2 gas introduced into the glass vacuum line, the gas mass flow introduced into the MS was reduced, and the change of δ13C accompanying this reduction was monitored. The sample gas split was changed to set the glass vacuum line (GVL):isotope ratio mass spectrometer (IRMS) ratio to 5:5, 8:2, and 9:1, and δ13C was measured for each ratio. It was confirmed that there was no effect on the isotopic fractionation accompanying the change in the sample gas split ratio. To prioritize the use of gas in the production of graphite, the GVL:IRMS ratio of 9:1 was chosen for this setup. The components are connected on-line, and up to 20 samples can be processed automatically.

This article presents a set of accelerator mass spectrometry (AMS) radiocarbon dates derived from human bone within burial contexts at CA-NAP-399 in Napa County, California, USA.

Ancient carbon reservoirs in freshwater bodies have the potential to introduce ancient carbon into charred cooking residues adhering to pottery wall interiors when aquatic organisms are parts of cooked resource mixes. This ancient carbon results in old apparent ages when these cooking residues are subjected to accelerator mass spectrometry dating, the so-called freshwater reservoir effect (FRE). Roper's (2013) assessment of the FRE on 14C ages from cooking residue in the Central Plains is only the second such peer-reviewed regional assessment in eastern North America. Roper suggests that 13 of 23 14C ages on residue are too old as a result of ancient carbon from fish or leached from shell temper or old carbon introduced via maize nixtamalization. Herein, we re-assess Roper's data set of 14C ages on cooking residues and annual plants and argue that she is mistaken in her assessment of the accuracies of 14C ages from residues. This outcome is placed in the context of the larger FRE literature.

Hart and Lovis clearly hold different views than do I about how to view incongruities in age determinations on food residue as compared to those on context dates on other short-lived materials. I explain how I came to the conclusions I drew in my earlier study (Roper 2013a) and suggest that I am evaluating my results, and those of others, by looking for patterns in the incongruities, rather than individually explaining away incongruent dates. I also briefly review some work with a collaborator being undertaken to correct the obvious problem with age-offset dates on residue.