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El Japón is a 16th century hamlet site in the marshlands of the southern Basin of Mexico in central Mesoamerica. Radiocarbon (14C) dating and OxCal modeling of human bone collagen (n = 11) identifies a range of burials at El Japón cemetery from 1550–1650 cal. CE. The refined chronology identifies use of this rural settlement well after the onset of colonial government-sponsored relocation of Indigenous people to larger settlements (congregaciones). Historically documented information in this work supports chronological modeling beyond stand-alone calibration. Stable isotopic study of bone samples demonstrates similar sources of dietary protein and carbohydrates. The similarity of carbon sources for bone apatite (bioapatite) and collagen offers security that both bone fractions are viable 14C dating opportunities. Recent extension of this work examines bioapatite 14C dates (n = 5) from the same bone samples when quality parameters are met—atomic carbon-nitrogen ratios of 3.2–3.3 and collagen yield of 10–20%. No significant difference is found between collagen and bioapatite dates of the same individuals (p = 0.17, Mann-Whitney U test). 14C dates from human bone samples in this primarily terrestrial dietary context can be successfully acquired from either collagen or bioapatite fractions.
There is a consensus in the literature that radiocarbon dating performed on bioapatite often produces ages younger than dating performed on collagen. We propose a general regression that could be used to convert the bioapatite radiocarbon ages to the simulated ages on collagen in fossil samples worldwide. This general regression presents several good indices of quality, high correlation (R2 = 0.98), lower values of percent predicted error (%PE = 0.01), and standard error of the estimate (%SEE = 21.83), showing that it is a good tool, as the predicted values are similar to those observed. Using this regression, we converted the radiocarbon ages of bioapatite to the expected age from the collagen fraction made for several taxa from the Brazilian Intertropical Region (BIR) and suggest that these dates could be 1–7 cal ka BP older than previously thought.
We inferred the annual isotopic diet (δ13C) of an individual of the giant ground sloth Eremotherium laurillardi found in Toca dos Ossos (Ourolândia, Bahia, Brazil) through the extension of its third inferior molar. This individual lived in the region at 40,779–39,617cal yr BP. One year of its life was recorded in a length of 67 mm in the tooth. Two years were recorded in this molariform, during which the diet and climate did not change much, and substantial precipitation occurred during the middle of the year, which is in opposition to the modern pattern. The mean carbon (μδ13C = −13.9 ± 1.8‰) and oxygen (μδ18O = 22.5 ± 2.9‰) isotopic values were similar to values for other individuals of the species found in the same cave but different from the values found in other localities of the Brazilian Intertropical Region, which allows us to suggest that this region had more precipitation and lower temperatures in comparison to today. The oxygen isotopic values found in dated fossils of E. laurillardi and from two other taxa found in the same cave (Toxodon platensis, and Notiomastodon platensis) could help in the understanding of the climatic variation that occurred in the region.
An international consortium of radiocarbon (14C) laboratories was established to date the origin of the St. George’s Rotunda in Nitrianska Blatnica (Slovakia), because its age was not well established in previous investigations. Altogether, 20 samples of wood, charcoal, mortar and plaster were analyzed. The 14C results obtained from the different laboratories as well as between the different sample types were in good agreement, resulting in a 14C calibrated age of 783–880 AD (94.2% probability) for the Rotunda. Although the 14C results have very good precision, the specific plateau-shape of the calibration curve in this period caused the wide range of the calibrated age. The probability distribution from OxCal calibration shows, however, that about 86% of the probability distribution lies in the period before 863 AD, implying that the Rotunda could have been constructed before the arrival of Constantine (St. Cyril) and St. Methodius to Great Moravia. The Rotunda thus probably represents the oldest standing purpose-built Christian church in the eastern part of Central Europe.
This paper raises methodological issues of radiocarbon (14C) dating of historical events based on data obtained during the excavations of the Russian medieval city of Yaroslavl. The city is of special interest to our study because of the precise time of its destruction by troops of Batu Khan mentioned in chronicles—the winter of 1238. To date in Yaroslavl, researchers have discovered 9 mass burials of citizens and domestic animals buried sometime after the massacre by the Mongols. Mass burials of people alongside animals in a common grave and outside of the cemetery, in violation of Christian traditions, are not typical of medieval Russia and are a sign of a military catastrophe. To test this hypothesis, we dated a total of 65 samples representing all 9 mass burials. A Bayesian chronological model of the accelerator mass spectrometry (AMS) dates narrowed the interval to the range of 1197–1280 cal AD, with the mean age of 1239 AD, consistent with the hypothesis that the studied mass burials of citizens and livestock are related to the capture of the city by the army of Batu Khan.
Stratigraphic records extending to Marine Oxygen Isotope Stage (MIS) 3 (57,000–29,000 cal yr BP) or older in Beringia are extremely rare. Three stratigraphic sections in interior western Alaska show near continuous sedimentological and environmental progressions extending from at least MIS 3, if not older, through MIS 1 (14,000 cal yr BP–present). The Kolmakof, Sue Creek, and VABM (vertical angle bench mark) Kuskokwim sections along the central Kuskokwim River, once a highland landscape at the fringe of central and eastern Beringia, contain aeolian deposition and soil sequences dating beyond 50,000 14C yr BP. Thick peaty soil, shallow lacustrine, and tephra deposits represent the MIS 3 interstade (or older). Sand sheet and loess deposits, wedge cast development, and very thin soil development mark the later MIS 3 period and the transition into the MIS 2 stade (29,000–14,000 cal yr BP). Loess accumulation with thicker soil development occurred between ~16,000–13,500 cal yr BP at the MIS 2 and MIS 1 transition. After ~13,500 cal yr BP, loess accumulation waned and peat development increased throughout MIS 1. These stratigraphic sequences represent transitions between a warm and moist period during MIS 3, to a cooler and more arid period during MIS 2, then a return to warmer and moister climates in MIS 1.
We sampled individual growth rings from three ancient remnant bald cypress (Taxodium distichum) trees from a massive buried deposit at the mouth of the Altamaha River on the Georgia Coast to determine the best technique for radiocarbon (14C) dating pretreatment. The results of our comparison of traditional ABA pretreatment and holocellulose and α-cellulose fractions show no significant differences among the pretreatments (<1 sigma) thereby suggesting that ABA pretreatment will prove sufficient for the development of a high-resolution 14C tree-ring chronology based on these ancient bald cypresses which will indicate whether the U.S. Southeast is subject to a regional radiocarbon offset.
It is known that 12C beam transmission through the accelerator decreases at high beam currents. This effect depends on machine design and varies across different types of AMS instruments. For beam currents of about 100 μA, the effect is small on the 500 kV tandem CAMS unit, whereas beam saturation is observed for similar high beam currents on the 250 kV SSAMS unit. While this effect is very evident for high 12C beam currents, we have also observed that even the 13C beam is found to suffer modest transmission loss with beam current. As a result, the 13C/12C ratio does not remain constant with beam current. By correcting for the effects of 12C beam saturation and decreased 13C transmission, we have obtained online δ13C values that are more accurate and precise at moderately high beam currents for SSAMS.
The Aqueduct is one of the city landmarks of Skopje, Republic of North Macedonia. It was part of a water-supply system, with a total original length of about 10 km, while its surface remains are about 385 m long. The age of the Aqueduct is not known—several hypotheses place it to periods between the 6th and 16th centuries. Six mortar samples from different positions of the eastern façade were taken for radiocarbon (14C) dating. In order to extract only the carbon associated to the time of building, three strategies for sample preparation were used: (1) mechanical separation of lime lumps formed during mortar hardening (2) selection on the basis of particle size and the ability to suspend in water induced by ultrasonic shock, and (3) collection of two gas CO2 fractions produced from the same bulk in reaction with acid. Characterization of fractions was performed by isotopic carbon composition and FTIR-ATR analyses. The most plausible results were obtained from lime lump fractions that were dated in the timeframe of 15th to 17th century.
In coastal and island archaeology, carbonate mollusk shells are often among the most abundant materials available for radiocarbon (14C) dating. The marsh periwinkle (Littorina irrorata) is one of these such species, ubiquitously found along the Atlantic and Gulf coasts of the United States in both modern and archaeological contexts. This paper presents a novel approach to dating estuarine mollusks where rather than attempting to characterize the size and variability of reservoir effects to “correct” shell carbonate dates, we describe a compound-specific approach that isolates conchiolin, the organic matter bound with the shell matrix of the L. irrorata. Conchiolin typically constitutes <5% of shell weight. In L. irrorata, it is derived from the snail’s terrestrial diet and is thus not strongly influenced by marine, hardwater, or other carbon reservoir effects. We compare the carbon isotopes (δ13C and Δ14C) of L. irrorata shell carbonate, conchiolin, and bulk soft tissue from six modern, live-collected specimens from Apalachicola Bay, Florida, with samples that represent possible sources of carbon within their environment including surface sediments, marsh plant tissues, and dissolved inorganic carbon (DIC) in water. Ultimately, this paper demonstrates that samples obtained from wet chemical oxidation of L. irrorata conchiolin produces accurate 14C dates.
There are hundreds of preserved medieval buildings in the mountainous part of Ingushetia, including Christian churches, crypts, temples, sanctuaries, battle towers, and living buildings. The chronology of their construction period is still questioned, as there are no radiocarbon (14C) dates published for these buildings and their dating is mainly based on architectural features, a few historical sources, and sometimes on accompanying archaeological material. The aim of this study is to assess more precisely the period of their construction. To do this, we selected the 10 most prominent medieval buildings that contain wooden construction elements and sampled these wooden elements in order to apply 14C accelerator mass-spectrometry dating (AMS) followed by wiggle-matching. From two of these buildings, plaster and mortar were also sampled for 14C AMS dating. This is the first time that these kinds of analyses have been performed for medieval buildings from the mountainous part of Ingushetia. For 6 out of 10 buildings, we acquired sufficiently precise dates that helped us to clarify their construction period. For the other 4 buildings, the acquired dates are still informative but could be refined further with additional 14C analyses. The calibrated dates obtained cover the period from AD 662 until recent time with the majority of them concentrated in 15th–17th centuries.
In order to evaluate effects of three land uses on isotopic compositions of CO2 and O2 of soil air to 5 m soil depth, a field study was conducted in the Calhoun Critical Zone Observatory, located in the subtropical climate of the Southern Piedmont of South Carolina, USA. Soil gas reservoirs were installed in ecosystems with three different land uses, each replicated three times: (i) reference hardwood stands that were never cultivated; (ii) currently cultivated plots; (iii) pine stands, which had been used for growing cotton in 19th century but were abandoned in about the 1930s and 1940s when they were regenerated with pines that are today 70–80 yr old. In addition to soil CO2 and O2 concentration measurements, soil gas samples were analyzed for Δ14C, δ13C, and δ18O. Stable carbon isotopic composition becomes lighter with the depth in soils of all three land uses: in the cultivated site δ13C decreases from –18‰ at 0.5 m to –21‰ at 5 m, in pine site from –22 to –25‰, and in hardwood from –21.5 to –24.5‰, respectively. Δ14C increased with depth from 40 to 60‰ in the top 0.5 m to about 80–140‰ at 5 m depending on land use. While surficial soils had relatively similar Δ14C in CO2, between 40 to 60‰ at 0.5 m, at 3 and 5 m, cultivated soils had the highest Δ14C, hardwood the lowest, and pine in between, a pattern that emphasizes the importance of contemporary respired CO2 in hardwood stands. Oxygen isotopic composition of CO2 did not change with depth, whereas free O2 was greatly enriched in lower horizons of forest soils, which we attribute to strong fractionation by respiration.
Biogeochemical analyses of eastern oysters (Crassostrea virginica) are frequently included in environmental monitoring and paleoecological studies because their shells and soft tissues record environmental and dietary signals. Carbon isotopes in the mineral phase of the shell are derived from ambient bicarbonate and dissolved inorganic carbon (DIC), while organic carbon present in soft tissue is of dietary origin. Mineral-bound organic matter within the carbonate shell matrix (“conchiolin”) is studied less frequently. The purpose of this study was to compare carbon isotope composition (δ13C and Δ14C) of conchiolin to those of shell carbonates and soft tissues in eastern oysters and assess the extent to which conchiolin can provide insight into paleoecological records. Eleven oyster specimens were live-collected from Apalachicola Bay, USA, as well as a set of environmental samples (water, sediment, and terrestrial plants). Overall, the δ13C values in all studied oyster tissue types record environmental signals related to carbon sources, with conchiolin being enriched in 13C by an average of 2.3‰ relative to bulk soft tissues. Δ14C values in oyster shell carbonates generally reflect the marine versus riverine source of DIC, while conchiolin Δ14C values are impacted by variable relative contributions of young and old organic matter. Environmental samples indicate a significantly large difference in Δ14C among sources, from –127‰ in particulate organic matter to approximately +15‰ in DIC. Conchiolin is significantly depleted in 14C relative to other tissue types, by as much as 56.6‰, posing a major obstacle to the use of conchiolin as an alternative material for radiocarbon dating.
Archaeological investigations of the age and origins of marine shell beads are important for understanding the emergence and maintenance of long-distance trade networks in prehistory. In this paper we expand upon and re-examine the incremental carbon (14C and δ13C) and oxygen (δ18O) isotope data from two Olivella biplicata shell beads from the LSP-1 Rockshelter, Oregon, USA, to address two common problems in dating marine shell trade goods: (1) the source region is large, adding to uncertainty regarding the appropriate specification of ΔR; and (2) the 14C activity within individual specimens is variable. Although this combination of factors severely limits the dating precision that is possible, we recommend a sampling and calibration approach that accounts for these added sources of uncertainty and minimizes the loss of precision. We recommend (1) sequential sampling in order to quantify the range of variability in 14C within shells; (2) a Bayesian calibration procedure that models the 14C dates as an ontogenetic sequence, in this case constrained by stable isotope sclerochronology; and (3) specifying ΔR in a manner that accounts for the full range of possible reservoir offsets in the source region.
Eastern oyster (Crassostrea virginica) is an ubiquitous estuarine shellfish taxon in eastern North America and one of the most abundant materials available for radiocarbon (14C) dating. We examine spatiotemporal variability in carbon reservoir effects among pre-bomb oysters from Apalachicola Bay, USA, a river-influenced estuary on the northern Gulf of Mexico. Shells were sampled at multiple points along the valve to produce time-series records of 14C variation during the lives of the mollusks. Conventional ages within shells differed by as little as 36 14C yr to as much as 295 14C yr. Reservoir offsets varied sub-regionally within the estuary, increasing from 92±37 yr in the eastern edge of study region to 227±110 yr in the west, reflecting the influence of 14C-depleted dissolved inorganic carbon from the Apalachicola River. Dynamic carbon reservoirs can pose problems for the estimation of ΔR and for building coastal chronologies. Estimating sub-regional ΔR values can be useful for assessing the range of variability in reservoir offsets within an estuary, and for correcting sample ages if the shell origin is known. Greater variability and/or uncertainty in ΔR lead to greater uncertainty in the calibrated age.
During the Pleistocene a fauna composed of large (biomass > 44 kg) and giant mammals (biomass > 1000 kg) that are usually associated with open environments lived in the Brazilian Intertropical Region. We present here new information concerning the paleoecology and chronology of some species of this megafauna. Carbon isotope analyses were performed for a better understanding of the paleoecology of the species Eremotherium laurillardi (Lund, 1842), Notiomastodon platensis (Ameghino, 1888) and Toxodon platensis (Owen, 1849). The δ13C data allow attributing a generalist diet to these species, which varied according to the kind of habitat in which they lived. In more open habitats all species were grazers; in mixed habitats E. laurillardi and T. platensis were mixed feeders, and N. platensis was grazer; and in more closed habitats all species were mixed feeders.
Combining atmospheric Δ14CO2 data sets from different networks or laboratories requires secure knowledge on their compatibility. In the present study, we compare Δ14CO2 results from the Heidelberg low-level counting (LLC) laboratory to 12 international accelerator mass spectrometry (AMS) laboratories using distributed aliquots of five pure CO2 samples. The averaged result of the LLC laboratory has a measurement bias of –0.3±0.5‰ with respect to the consensus value of the AMS laboratories for the investigated atmospheric Δ14C range of 9.6 to 40.4‰. Thus, the LLC measurements on average are not significantly different from the AMS laboratories, and the most likely measurement bias is smaller than the World Meteorological Organization (WMO) interlaboratory compatibility goal for Δ14CO2 of 0.5‰. The number of intercomparison samples was, however, too small to determine whether the measurement biases of the individual AMS laboratories fulfilled the WMO goal.
Strombus alatus and Busycon sinistrum are large marine gastropods that are frequently recovered from archaeological contexts in southeastern North America. We previously proposed a reservoir age offset (ΔR) for B. sinistrum from the northern Gulf of Mexico region based on known-age pre-bomb 20th-century specimens. We also reported significant variability in radiocarbon both among and within S. alatus specimens, which precluded a reliable estimation of ΔR for this taxon. In this paper, we present a complementary data set from archaeological contexts to re-evaluate marine reservoir effects in the northern Gulf Coast region at multiple spatial and temporal scales. The new data set consists of a total of 13 14C age determinations from well-associated marine (B. sinistrum and S. alatus) and terrestrial (Odocoileus virginianus) samples from a closed context at the Bayou St. John (1BA21) archaeological site. We suggest a slightly updated ∆R value of –2±53 14C yr for late Holocene-age B. sinistrum from the northern Gulf Coast region. S. alatus, and possibly other species of strombid conchs, are poor candidates for 14C dating due to the highly variable 14C content observed within and among specimens. Though subregional variability in inputs of 14C-depleted waters is likely, life-history factors related to ontogenetic niche and/or habitat shifts appear to be a major influence in shell 14C for S. alatus.
Radiocarbon ages were determined on different fractions extracted from buried paleosols in south-central Alaska as an experiment to establish best practices for analysis of low-organic-matter paleosols. Seven samples were collected from directly beneath tephra deposits to determine the eruption frequency of Mount Spurr Volcano, Alaska. Soil development near the volcano is poor due to the high-latitude climate and frequent burial of soil surfaces by tephra. Contamination of soils by local wind-blown material is a concern. The humic acid 14C ages are consistently younger than both the bulk soil and residue after extraction ages. The difference in ages between the humic acid extract and bulk soil range from 60–1130 14C yr BP and 180–4110 14C yr BP, respectively, for residue. Previous observations from dating different soil fractions show that residue ages are typically younger than humic acid extracts presumably because they contain a fraction of younger plant material including roots. We attribute the older ages to contamination by old carbon from eolian charcoal particles. This study supports the use of accelerator mass spectrometry (AMS) 14C dating of the humic acid fraction in order to estimate the age of soil that presumably marks the age of burial and avoids suspected contamination by old carbon.