14C Data Sets Research Articles

Comments on Graf, Journal of Archaeological Science 36, 2009 “ “The Good, the Bad, and the Ugly”: evaluating the radiocarbon chronology of the middle and late Upper Paleolithic in the Enisei River valley, south-central Siberia”

Here I present a critical evaluation of the analysis conducted by Graf [Graf, K.E., 2009. “The Good, the Bad, and the Ugly”: Evaluating the radiocarbon chronology of the middle and late Upper Paleolithic in the Enisei River valley, south-central Siberia. Journal of Archaeological Science 36, 694–707] of the Paleolithic radiocarbon ( 14C) dataset for the Upper Paleolithic sites in the Yenisei River basin of Central Siberia. Graf applied a rating system to the corpus of existing 14C data for the region, and announced some new 14C dates. The results obtained, however, are highly biased due to several factors, including prejudice concerning the higher accuracy of the AMS technique in 14C dating and that 14C dates from the same cultural component should overlap with plus–minus two sigmas; ambiguities with the subdivision of the Lateglacial period; artificially high sample selection criteria; incomplete factual material; and unjustifiable and misleading statements on the 14C dating of fossil bones and the issue of Last Glacial Maximum human presence in Siberia. As a result, the conclusions made by Graf [Graf, K.E., 2009. “The Good, the Bad, and the Ugly”: Evaluating the radiocarbon chronology of the middle and late Upper Paleolithic in the Enisei River valley, south-central Siberia. Journal of Archaeological Science 36, 694–707] are unconvincing. New analysis is necessary in order to improve the quality of treatment of the original data for the Upper Paleolithic 14C chronology in the Yenisei River basin.

A new age model for the sediment cores from Academician ridge (Lake Baikal) based on high-time-resolution AMS 14C data sets over the last 30 kyr: Paleoclimatic and environmental implications

We constructed a new age model based on high-time-resolution 14C data sets from three sediment cores from Academician ridge, Lake Baikal, for reconstruction of environmental and biological changes in southern Siberia during the last ca. 30 kyr. We used 14C ages of total organic carbon (TOC) for the model, because terrestrial plant residues and biogenic carbonate were not observed in the sediments. For accurate dating and age models based on 14C ages of TOC, the freshwater 14C reservoir effect and the effect of dead carbon from land-derived organic materials must be estimated. In this study, we estimated the correction factor for these effects to be 2100 ± 90 yr, on the basis of a key layer, the “ 14C plateau”, caused by changes in the atmospheric 14C concentration during the Younger Dryas (YD) cooling event. The new age scale, along with the TOC mass accumulation rate (MAR TOC) and stable carbon isotope ratio in the sediment cores, clearly indicate a rapid decrease in lake productivity and reduced influx of terrestrial organic materials into the lake during the YD (12.8–11.6 cal ka BP). Productivity was high (MAR TOC, up to 19.7 mg/cm 2·kyr) in and around Lake Baikal during 9.3–6.4 cal ka BP (Holocene climate optimum). Moreover, paleoproductivity changes during the last ca. 30 kyr in and around the Lake Baikal were clearly associated with fluctuations in the East Asian monsoon intensity, as inferred from the δ 18O record from Sanbao and Hulu caves, China, during the late Quaternary (Wang et al., 2008. Nature 451, 1090–1093).

New and revised 14C dates for Hawaiian surface lava flows: Paleomagnetic and geomagnetic implications

Radiocarbon dates have been obtained for 30 charcoal samples corresponding to 27 surface lava flows from the Mauna Loa and Kilauea volcanoes on the Island of Hawaii. The submitted charcoal was a mixture of fresh and archived material. Preparation and analysis was undertaken at the NERC Radiocarbon Laboratory in Glasgow, Scotland, and the associated SUERC Accelerator Mass Spectrometry facility. The resulting dates range from 390 years B.P. to 12,910 years B.P. with corresponding error bars an order of magnitude smaller than previously obtained using the gas‐counting method. The new and revised 14C data set can aid hazard and risk assessment on the island. The data presented here also have implications for geomagnetic modelling, which at present is limited by large dating errors.

High-time resolution AMS 14C data sets for Lake Baikal and Lake Hovsgol sediment cores: Changes in radiocarbon age and sedimentation rates during the transition from the last glacial to the Holocene

High-time resolution 14C dating of Lake Baikal sediment cores indicates negative and positive anomalies of calculated linear sedimentation rate (LSR; 1.1 and 35.6 cm/ka, respectively) during the period of climate transition from the last glacial to Holocene. The timing of the Lake Baikal apparent LSR anomalies is consistent with that of the changes in the atmospheric radiocarbon concentration (Δ 14C) during Younger Dryas rapid cooling event. 14C dating of lipids in the Lake Baikal surface sediments revealed that the sources of sedimentary lipids were different in each basin. In the Northern Basin of Lake Baikal, the 14C age of total lipids from the surface sediment (4.0 14C ka) was found to be older than that of TOC (1.6 14C ka). By contrast, the 14C age of total lipids in the Southern Basin was younger than that of the TOC by ca. 0.7–3.0 ka. In the Lake Hovsgol sediment cores, ages of the main lithologic boundaries during the last glacial–interglacial transition were estimated based on new 14C data sets. TOC concentration in the cores started to rapidly increase at 13.8 ± 0.3 14C ka at the base of the basinwide finely laminated layer deposited during Bølling/Allerød. The base of the layer diatomaceous mud corresponds to the end of Younger Dryas event (10.6 ± 0.1 14C ka).

Lateglacial environmental variability from Swiss tree rings

Evidence of annually resolved environmental variations during the Allerød interstadial is presented using 81 fossil Scots pine tree-ring series from Gaenziloo and Landikon, near Zurich, Switzerland. The absolute age of the trees ranges between 11,920 and 10,610 14C BP, which was determined by wiggle-matching radiocarbon ages to the Cariaco 14C data set. From the two sites we created a composite floating Allerød chronology on the basis of their 632 years of overlap ( r=0.57), after individual spline detrending. Merging both data sets resulted in a Lateglacial tree-ring chronology covering 1050 years. Regional curve standardization (RCS) was applied to preserve low-frequency information. Growth behavior of the fossil trees was compared with a recent composite pine data set from the central Swiss Alps and reveals distinct differences. The new Allerød RCS chronology reveals major Lateglacial variations, such as the Gerzensee oscillation, the abrupt climate shift towards the Younger Dryas and some short-term events. Radiocarbon ages agree well with those from other sites on the Swiss Plateau. For hemispheric comparisons we used the annual layer thickness record from the NGRIP ice core and the gray-scale varve record from the Cariaco basin. Even though the amplitudes are not yet fully understood, similarities on decadal-to-centennial scales are apparent.

High-precision Radiocarbon Dating with Accelerator Mass Spectrometry and Calibration of Radiocarbon Ages

High-resolution as well as high-precision age estimation is particularly important for Quaternary research to realize its main aim of better understanding of global environmental changes of the past and realistic prediction of the changes in the near future. Among several dating methods that are applicable to Quaternary samples, radiocarbon (14C) dating has been commonly used since its development in late 1940s.A new 14C detection technique, accelerator mass spectrometry (AMS), has been developed since 1977. The method directly detects and counts 14C atoms, instead of counting β-ray emitted in the decay of 14C, and therefore requires only a few mg of carbon for 14C measurements. Nowadays, AMS 14C dating is widely used and more than sixty AMS 14C facilities are in operation in the world. In Japan, eight facilities for AMS 14C dating have been in use since 2004.As one of the eight AMS 14C measurement systems in Japan, the Nagoya University AMS group has started routine 14C measurements with the firstly introduced Tandetron AMS system since 1983 and also with the secondly established Tandetron AMS since 1999. The second system has an excellent performance of the standard deviation (one sigma) of the 14C/12C ratios of around ±0.2% to ±0.4% (±17-±30 14C yrs) and that of the corresponding 13C/12C ratios of ±0.03% to ±0.07%, as are tested for HOxII targets. By using this AMS system, we are now trying to provide accurate ages to the Quaternary events. Briefly discussed in this article are, (1) a consistency test of the established IntCal98 and IntCal04 14C data sets with the 14C-concentration records in Japanese tree rings ; (2) programs of high accuracy and precision age estimation by 14C wiggle matching techniques for wood samples ; (3) investigations of 14C reservoir effect for marine samples from the Japanese Archipelago.

Late Pleistocene and Holocene glaciation in the Pyrenees: a critical review and new evidence from 10Be exposure ages, south-central Pyrenees

A compilation and a critical assessment of the 14C data set available show that the chronology of glacial events in the Pyrenees is not well constrained. After reviewing the literature on glacial reconstruction, we suggest a simplified subdivision of the Pyrenean last glacial cycle record into Last Pleniglacial, Deglaciation, and Neoglacial. To improve the numerical glacial chronology, we provide 10Be surface exposure ages for 5 glacial erosion surfaces, 9 moraines and 2 erratics in the Upper Noguera Ribagorçana Valley (south-central Pyrenees). Published corrected 14C data and new 10Be exposure ages indicate that the major phase of moraine building recorded in this valley during the Last Pleniglacial probably occurred after 25 ka BP. This age calls in question the generally accepted hypothesis of a very early deglaciation of the Pyrenees ca 70–40 ka BP, and strongly suggests that the Pyrenees could have been in pleniglacial conditions during the Last Glacial Maximum (LGM). However, we do not exclude the possibility that the maximum glacier extent during the last glacial cycle had taken place much earlier than the LGM, as indicated by some published U-Th, AMS 14C and OSL data. We suggest that pleniglacial conditions could have taken place during a longer (⪢30–20 ka) period than generally assumed, and that the Last Pleniglacial could include several glacier fluctuations recorded irregularly in different valleys, with a last major glacier readvance taking place around the LGM. In addition, the Deglaciation is represented by a series of moraines deposited between ca 13.7±0.9 and 10.1±0.6 ka. This moraine series indicates a highly variable climatic pattern that is partly correlated with Greenland Stadial 1 (the Younger Dryas), and suggests that the Deglaciation could have continued into the early Holocene.

Radiocarbon variations from the Southern Hemisphere, 10,350–9700 cal BP

We have made AMS measurements on a series of 10-ring samples from a subfossil Huon pine log found in western Tasmania (42°S, 145°E). The results show a pronounced rise in Δ14C over the first 200 years, and a decrease over the following 160 years.Tree-ring width measurements indicate that this log (catalogue SRT-447) can be cross-dated with another subfossil log (SRT-416) for which a series of high-precision radiometric 14C measurements have previously been made. When the two tree-ring series are thus aligned, SRT-447 is the older of the two logs, and there is a 139-year overlap. We then have a Huon pine floating chronology spanning 680 years, with 14C measurements attached. The 14C data sets agree well within the period of overlap indicated by the tree-rings.The 14C variations from Huon pine show excellent agreement with those from German oak and pine for the period 10,350–9670 cal BP. Aligning the Huon pine 14C series with that from German oak and pine allows us to examine the inter-hemispheric offset in 14C dates in the early Holocene.

Review of Tropospheric Bomb 14C Data for Carbon Cycle Modeling and Age Calibration Purposes

Comprehensive published radiocarbon data from selected atmospheric records, tree rings, and recent organic matter were analyzed and grouped into 4 different zones (three for the Northern Hemisphere and one for the whole Southern Hemisphere). These 14C data for the summer season of each hemisphere were employed to construct zonal, hemispheric, and global data sets for use in regional and global carbon model calculations including calibrating and comparing carbon cycle models. In addition, extended monthly atmospheric 14C data sets for 4 different zones were compiled for age calibration purposes. This is the first time these data sets were constructed to facilitate the dating of recent organic material using the bomb 14C curves. The distribution of bomb 14C reflects the major zones of atmospheric circulation.

The Comparison of 14C Wiggle-Matching Results for the ‘Floating’ Tree-Ring Chronology of the Ulandryk-4 Burial Ground (Altai Mountains, Siberia)

Two independent 14C data sets of 10 tree-ring samples from the longest master chronology of the Pazyryk cultural complex were obtained and wiggle-matched to the absolute timescale. The results show very good agreement, within 10–15 calendar yr. The Ulandryk-4 burial ground (mound 1) was dated to about 320–310 cal BC, and this is consistent with wiggle-matching of the Pazyryk burial ground date series.

Palaeolithic radiocarbon chronology: quantifying our confidence beyond two half-lives

It is now three decades since Waterbolk introduced evaluation criteria to 14C chronology. Despite this, and other subsequent attempts to introduce quality control in the use of 14C data, no systematic procedure has been adopted by the archaeological community. As a result, our databases may be significantly weakened by questionable dates and/or questionable associations between dated samples and the archaeological phenomena they are intended to represent. As the use of chronometric data in general becomes more ambitious, we must pause and assess how reliable these data are. Here, we forward a set of evaluation criteria which take into account archaeological (e.g. associational, stratigraphic) and chronometric (e.g. pre-treatment and measurement) criteria. We intend to use such criteria to evaluate a large 14C dataset we have assembled to investigate Late Glacial settlement in Europe, the Near East and North Africa, supported by the Leverhulme Trust. We suggest that the procedure presented here may at least form the basis of the development of more rigorous, scientific use of 14C dates.

High-precision AMS radiocarbon measurements of central Arctic Ocean sea waters

We report on the first sub-5%. precision radiocarbon dataset measured on single targets using accelerator mass spectrometry (AMS). A 13 sample water column profile collected in the Canada Basin (74°N, 150°W, 3850 m water depth) of the central Arctic Ocean in September 1992 has been analyzed in duplicate and the average total precision achieved for the 26 targets is ± 3.2%.. The reproducibility of the 13 paired analyses averages +- 4.8%. as determined by a chi-square fit minimization for a quality factor of unity, and ± 7.8%. using ANOVA. Eliminating two of the 13 paired analyses because of apparent outlier behavior in one of the two analyses comprising the pair results in a total precison of ± 3.2%., a chi-square fit of ± 3.5%., and ANOVA precision of ± 3.5%.. Comparison with a recently published AMS 14C profile from the same basin suggests these data are accurate as well. Results show that the deep waters of the Canada Basin have a renewal rate of 430 years, in comparison with 250 years estimated for the deep waters of the Eurasian Basin. Although the major requirement of the World Ocean Circulation Experiment (WOCE) for a radiocarbon analysis precision of ± 3 to 4%. for deep water samples can now be met with the AMS technology available at the National Ocean Sciences AMS Facility at the Woods Hole Oceanographic Institution for single-target analyses, a careful program of duplicate analyses should be included to insure the highest quality in the WOCE Δ 14C dataset.