Academic literature on the topic 'Radiocarbon calibration'

The following radiocarbon determinations were measured in the Radiocarbon Dating laboratory of the Department of Geology, University of Wales College of Cardiff. Calibrations are derived from the University of Washington, Quaternary Isotope Lab., Radiocarbon Calibration Program 1987, Rev. 2.O.

We have developed a software utility, “DateLab”, for conventional radiocarbon age (CRA) calibration and Bayesian analysis of CRAs. The current version has a smaller range of applicability than other similar utilities such as Bcal, Oxcal, and Mexcal. However, it enables analysis of some common types of CRA datesets. The main advantages of DateLab are its high quality sampling algorithm, the possibility of carrying out model comparison and hypothesis testing in a straightforward way, and the unbiased character of the summary statistics on which the analysis depends.

Variations in atmospheric 14C content complicate the conversion of conventional 14C ages BP (i.e., years before AD 1950) into real calendar ages (AD/BC) (de Vries 1958; Willis, Tauber & Münnich 1960). These variations are indirectly observed in tree rings from European and North American wood. In recent decades, measurements made on dendrochronologically dated wood have resulted in the generally accepted Stuiver and Pearson calibration curves. These curves, together with other calibration data, were published in the first Radiocarbon Calibration Issue (Stuiver & Kra 1986), and are extended in the present Calibration Issue (Stuiver, Long & Kra 1993).

Radiocarbon calibration is a fundamental stage of the radiocarbon dating process if meaningful calendar ages are to be derived from samples’ radiocarbon determinations. However, the present limit of direct, non-reservoir-corrected, atmospheric radiocarbon calibration is 12,550 calibrated years before present (Reimer et al. 2009), leaving approximately three quarters of the radiocarbon timescale to be necessarily calibrated via less secure marine records. The sediment profile of Lake Suigetsu, Honshu Island, central Japan, offers an ideal opportunity from which to derive an extended, ‘wholly terrestrial’ and continuous record of atmospheric radiocarbon back to the limits of radiocarbon detection (circa 60,000 years before present). The presence of well-defined, annually-deposited laminae (varves) throughout this extended time period provides an independent, high resolution chronometer against which radiocarbon measurements, performed upon plant macrofossil samples retrieved from the sediment column, can be directly related. This site was first exploited for radiocarbon calibration purposes by Kitagawa and van der Plicht (1998a, 1998b), however, issues pertaining to the reliability of the calendar age scale of this work precluded the widespread uptake of this dataset. The work presented in this DPhil thesis represents a significant contribution to the broader, ‘Suigetsu Varves 2006’ project – an international collaboration centring on the re-coring of Lake Suigetsu, which was undertaken in summer 2006 to improve upon the shortcomings of the previous project and, thereby, to fully exploit the site’s potential for both radiocarbon calibration and multi-proxy palaeoenvironmental study (Nakagawa et al. 2011). This DPhil thesis describes the generation of the revised (‘SG06’) terrestrial radiocarbon calibration dataset from Lake Suigetsu, comprising 647 accelerator mass spectrometry (AMS) radiocarbon determinations, and extending across the complete range of the radiocarbon dating method. Furthermore, visual matching of archive SG93 core sections to the continuous SG06 sediment profile was undertaken, allowing the integration of the ≈ 300 radiocarbon determinations from the original Lake Suigetsu project into a higher resolution (≈ 900 radiocarbon measurements), combined Lake Suigetsu radiocarbon calibration dataset, providing a unique reconstruction of atmospheric radiocarbon across the entire radiocarbon dating timescale.

The main intention of the PhD project was to create a varve chronology for the Suigetsu Varves 2006' (SG06) composite profile from Lake Suigetsu (Japan) by thin section microscopy. The chronology was not only to provide an age-scale for the various palaeo-environmental proxies analysed within the SG06 project, but also and foremost to contribute, in combination with the SG06 14C chronology, to the international atmospheric radiocarbon calibration curve (IntCal). The SG06 14C data are based on terrestrial leaf fossils and therefore record atmospheric 14C values directly, avoiding the corrections necessary for the reservoir ages of the marine datasets, which are currently used beyond the tree-ring limit in the IntCal09 dataset (Reimer et al., 2009). The SG06 project is a follow up of the SG93 project (Kitagawa & van der Plicht, 2000), which aimed to produce an atmospheric calibration dataset, too, but suffered from incomplete core recovery and varve count uncertainties. For the SG06 project the complete Lake Suigetsu sediment sequence was recovered continuously, leaving the task to produce an improved varve count. Varve counting was carried out using a dual method approach utilizing thin section microscopy and micro X-Ray Fluorescence (µXRF). The latter was carried out by Dr. Michael Marshall in cooperation with the PhD candidate. The varve count covers 19 m of composite core, which corresponds to the time frame from ≈10 to ≈40 kyr BP. The count result showed that seasonal layers did not form in every year. Hence, the varve counts from either method were incomplete. This rather common problem in varve counting is usually solved by manual varve interpolation. But manual interpolation often suffers from subjectivity. Furthermore, sedimentation rate estimates (which are the basis for interpolation) are generally derived from neighbouring, well varved intervals. This assumes that the sedimentation rates in neighbouring intervals are identical to those in the incompletely varved section, which is not necessarily true. To overcome these problems a novel interpolation method was devised. It is computer based and automated (i.e. avoids subjectivity and ensures reproducibility) and derives the sedimentation rate estimate directly from the incompletely varved interval by statistically analysing distances between successive seasonal layers. Therefore, the interpolation approach is also suitable for sediments which do not contain well varved intervals. Another benefit of the novel method is that it provides objective interpolation error estimates. Interpolation results from the two counting methods were combined and the resulting chronology compared to the 14C chronology from Lake Suigetsu, calibrated with the tree-ring derived section of IntCal09 (which is considered accurate). The varve and 14C chronology showed a high degree of similarity, demonstrating that the novel interpolation method produces reliable results. In order to constrain the uncertainties of the varve chronology, especially the cumulative error estimates, U-Th dated speleothem data were used by linking the low frequency 14C signal of Lake Suigetsu and the speleothems, increasing the accuracy and precision of the Suigetsu calibration dataset. The resulting chronology also represents the age-scale for the various palaeo-environmental proxies analysed in the SG06 project. One proxy analysed within the PhD project was the distribution of event layers, which are often representatives of past floods or earthquakes. A detailed microfacies analysis revealed three different types of event layers, two of which are described here for the first time for the Suigetsu sediment. The types are: matrix supported layers produced as result of subaqueous slope failures, turbidites produced as result of landslides and turbidites produced as result of flood events. The former two are likely to have been triggered by earthquakes. The vast majority of event layers was related to floods (362 out of 369), which allowed the construction of a respective chronology for the last 40 kyr. Flood frequencies were highly variable, reaching their greatest values during the global sea level low-stand of the Glacial, their lowest values during Heinrich Event 1. Typhoons affecting the region represent the most likely control on the flood frequency, especially during the Glacial. However, also local, non-climatic controls are suggested by the data. In summary, the work presented here expands and revises knowledge on the Lake Suigetsu sediment and enabls the construction of a far more precise varve chronology. The 14C calibration dataset is the first such derived from lacustrine sediments to be included into the (next) IntCal dataset. References: Kitagawa & van der Plicht, 2000, Radiocarbon, Vol 42(3), 370-381 Reimer et al., 2009, Radiocarbon, Vol 51(4), 1111-1150
Die Hauptzielsetzung der Doktorarbeit war die Erstellung einer Warvenchronologie für das Kompositprofil der "Suigetsu Varves 2006" (SG06) Sedimentbohrung vom Suigetsu See durch Dünnschliffmikroskopie. Die Chronologie soll dabei nicht nur als Altersskala für die unterschiedlichen Proxies, die im Rahmen des SG06 Projekts bearbeitet werden, dienen, sondern in Kombination mit der SG06 14C Chronologie auch zur Verbesserung der internationalen Radiokarbon Kalibrationskurve (IntCal) beitragen. Da die SG06 14C Daten aus fossilen, in den See eingewehten Blättern gewonnen wurden, geben sie den 14C Gehalt der Atmosphäre direkt wieder. Das heißt, dass Korrekturen entfallen, wie sie bei den derzeit im IntCal09 Datensatz (Reimer et al., 2009) genutzten marinen 14C Daten notwendig sind. Das SG06 Projekt ist ein Folgeprojekt des SG93 Projekts (Kitagawa & van der Plicht, 2000), welches ebenfalls die Erstellung eines Kalibrationsdatensatzes zur Zielsetzung hatte. Allerdings war das Sedimentprofil der SG93 Bohrung unvollständig und die Warvenchronologie unzureichend genau. Im Rahmen des SG06 Projekts wurde die komplette Sedimentabfolge des Sees erbohrt, so dass die Erstellung einer verbesserten Warvenchronologie als Aufgabe verblieb. Für die Erstellung der Warvenchronologie kam neben Dünnschliffmikroskopie eine zweite, unabhängige Zähltechnik zum Einsatz, die Mikro-Röntgenfluoresenz (µXRF) Daten nutzt. Diese Zählung wurde von Dr. Michael Marshall in Zusammenarbeit mit dem Doktoranden erstellt. Insgesamt wurden in 19 m des SG06 Sedimentprofils Warven gezählt, was dem Zeitabschnitt zwischen ≈10 und ≈40 ka BP entspricht. Die Warvenzählung zeigte, dass sich nicht jedes Jahr saisonale Lagen ausgebildet hatten und die Zählungen von beiden Techniken damit unvollständig waren. Dieses Problem tritt bei Warvenzählungen häufiger auf und wird in der Regel durch manuelle Interpolation der fehlenden Lagen gelöst. Allerdings hat der manuelle Ansatz Schwächen. Zum einen kann es zu subjektiven Ungenauigkeiten kommen, zum anderen wird die durchschnittliche Sedimentationsrate (welche die Grundlage der Interpolation ist) in der Regel aus benachbarten, gut warvierten Bereichen abgeleitet. Das setzt jedoch voraus, dass die Sedimentationsrate in den benachbarten Intervallen identisch mit der im zu interpolierenden Bereich ist, was nicht zwingend der Fall ist. Um diese Probleme zu umgehen wurde für die vorliegende Arbeit eine neuartige Interpolationsmethode entwickelt. Diese ist computergestützt und automatisiert und Ergebnisse daher objektiv und reproduzierbar. Weiterhin wird die Sedimentationsrate direkt aus dem zu interpolierenden Bereich bestimmt, indem die Abstände der auftretenden saisonalen Lagen statistisch ausgewertet werden. Daher kann die Methode auch für Profile ohne gut warvierte Bereiche eingesetzt werden. Ein weiterer Vorteil des neuen Interpolationsprogramms ist, dass ein objektiver Interpolationsfehlers berechnet wird. Die interpolierten Ergebnisse der beiden Zähltechniken wurden kombiniert und um nachzuweisen, dass es sich bei der resultierenden Chronologie um ein zuverlässiges Ergebnis handelt, wurde diese mit der mit IntCal09 kalibrierten 14C Chronologie vom Suigetsu See verglichen. Dabei wurde nur der Abschnitt berücksichtigt, in dem IntCal09 auf dendrologischen Daten beruht (bis 12,55 ka cal BP). Der Vergleich zeigte, dass die finale Warvenchronologie innerhalb des 68,2% Fehlerbereichs der 14C Datierungen lag. Das heißt, dass die Interpolationsmethode hinreichend genaue und zuverlässige Ergebnisse erzielt. Die Genauigkeit wurde weiter verbessert, indem die Chronologie mit U-Th Altern von Speläothemen modelliert wurde, wobei die tieffrequenten Signale der 14C Daten als Verbindung zwischen Suigetsu und den Speläothemen verwendet wurde, was die Konstruktion eines verbesserten Kalibrationdatensatzes erlaubte. Die modellierte Chronologie stellt dabei auch die Altersskale für die im SG06 Projekt analysierten Proxies dar. Ein Proxy der im Rahmen der Doktorarbeit untersucht wurde war die Verteilung von Ereignislagen. Diese sind in der Regel Anzeiger für Flutereignisse oder Erdbeben. Die mikrofazielle Untersuchung der Ereignislagen zeigte drei verschiedene Lagentypen auf, wobei zwei davon hier erstmals für den Suigetsu See beschrieben sind. Die Lagentypen sind: Matrix dominierte Lagen als Ergebnis von Seegrundrutschungen, Turbidite als Ergebnis von Hangrutschungen und Turbidite als Ergebnis von Flutereignissen. Die ersten beiden Lagentypen wurden vermutlich durch Erdbeben ausgelöst. Die große Mehrheit der Ereignislagen ist jedoch auf Flutereignisse zurückzuführen (362 von 369). Dies erlaubte die Rekonstruktion der Hochwasserhäufigkeit für die letzten 40 ka. Dabei zeigten sich starke Schwankungen über den analysierten Zeitraum. Die höchsten Werte wurden während des glazialen Meeresspiegelminimums erreicht während die niedrigsten Werte im Zusammenhang mit Heinrich Ereignis 1 auftraten, was vermutlich in erster Linie mit der Taifunhäufigkeit in der Region zusammenhängt. Allerdings zeigten die Daten auch Einflüsse von lokalen, nicht Klima getriebenen Prozessen. Zusammenfassend kann gesagt werden, dass die hier vorliegende Arbeit die Kenntnisse über die Sedimente des Suigetsu Sees deutlich erweitert hat und die Revidierung einiger älterer Interpretationen nahe legt. Die verbesserte Warvenchronologie trug zu einem deutlich verbesserten Kalibrationsdatensatz bei. Dieser ist der erste aus lakustrinen Daten gewonnen Datensatz, der in den (kommenden) IntCal Datensatz eingearbeitet werden wird. Quellennachweis: Kitagawa & van der Plicht, 2000, Radiocarbon, Vol 42(3), 370-381 Reimer et al., 2009, Radiocarbon, Vol 51(4), 1111-1150

Chavín de Huántar is one of the key sites of the Formative Period in the Central Andes, with many decades of investigations by dozens of investigators, but ironically its chronology is still poorly defined and contested. This article reviews the historical evidence for Chavín chronology, emphasizing an examination of calibrated radiocarbon dates, and summarily reviewing related radiocarbon evidence from approximately contemporary sites. The more voluminous C14 evidence from recent work at Chavín is then examined, particularly focused on dates from known ceramic and architectural contexts. A large number of determinations concur, both in and outside of Chavín, in dating stamped polished blackware "janabarroide" ceramics in the range of 800-500 BC in calibrated age. Earlier and later occupations at Chavín are documented, helping confirm this time range for "Early Horizon" materials. Chavín, unlike some other important Formative sites, loses its temple function by around 500 BC calibrated, although major construction seems to have greatly decreased well before that time.
Chavín de Huántar es uno de los sitios fundamentales para entender el Periodo Formativo en los Andes centrales. Irónicamente, a pesar de muchas décadas de investigaciones realizadas por docenas de investigadores, su cronología es todavía debatida e insegura. Este artículo presenta una reseña de la evidencia histórica para la cronología de Chavín, enfatizando la contribución de los fechados radiocarbónicos calibrados y, de manera breve, revisando los que están temporalmente relacionados con otros sitios formativos. Se analizan, también, los numerosos fechados de carbono-14 asociados a cerámica y contextos arquitectónicos conocidos en Chavín derivados de estudios recientes. De hecho, muchos fechados de Chavín y sitios relacionados concuerdan en ubicar a la cerámica negra pulida estampada, denominada janabarroide, alrededor de 800-500 a.C. (calib.). La presencia de ocupaciones anteriores y posteriores, documentadas con fechados, ayudan a confirmar este rango temporal para materiales reconocidos del "Horizonte Temprano". En contraste con algunos otros importantes sitios formativos, Chavín deja de funcionar como templo hacia 500 a.C. (calib.), aunque los esfuerzos destinados a las construcciones principales ya estaban disminuyendo, de manera notable, antes de esta época.

¹⁴C wiggle-matching was applied to two wood samples closely related to geological and archaeological events with associated dendrochronological dates, to demonstrate the accuracy of ¹⁴C dating with accelerator mass spectrometry (AMS). Wiggle-matching on charred wood with bark, excavated from a pyroclastic mud-flow deposited by the huge 10th Century eruption of the Baitoushan Volcano, revealed the eruption age as cal A.D. 935 +8/-5 with 95% confidence. This date is consistent with the eruption age of A.D. 912 to A.D. 972 estimated by dendrochronology on two wooden boards that had clear stratigraphical connections to the B-Tm tephra deposit in Japan, an ash fall layer formed by the eruption of the Baitoushan Volcano. The date is also consistent with an A.D. 937–938 date estimated by the analysis of varved sediments from Lake Ogawarako in Aomori prefecture. The other wooden board collected from the Mawaki archaeological site in Ishikawa prefecture was wiggle-matched as 783 +13/-11 cal B.C. with 95% confidence, which is consistent with the dates of 830 cal B.C. to 759 cal B.C. obtained for seven wooden poles from the same wooden structures as the wooden board. These results are highly encouraging for obtaining accurate dates on wood when dendrochronology cannot be used.

第19回名古屋大学年代測定総合研究センターシンポジウム平成18(2006)年度報告<第1部> Proceedings of the 19th symposiumon on Chronological Studies at the Nagoya University Center for Chronological Research in 2006 日時:平成19 (2007)年1月15日(月)～17日(水) 会場:名古屋大学シンポジオン Date:January15th-17th, 2007 Venue:Nagoya Uhiversity Symposion Hall

The Baraba Early Neolithic culture was allocated on the archaeological materials of Tartas-1 site. The set of radiocar- bon dates was received in the Curt-Engelhorn-Centre Archaeometry (Germany) and on the “Accelerator Mass Spec- trometer of the Budker Institute of Nuclear Physics SB RAS” (AMS BINP SB RAS, Russia). The radiocarbon calibration of this set of dates with 1-sigma and 2-sigma demonstrates the total correlation with the dates provided by the laboratory of Heidelberg University; several of them are even identical. Therefore, the correlation of dates received in the different laboratories reaffirms the dating of Tartas-1 site which is 7th millennium BCE. The Baraba archaeological culture has the same dating. The results were published (Molodin et al., 2019).