Misunderstandings Concerning the Significance of AMS Background 14C Measurements

Radiocarbon ◽  
2018 ◽  
Vol 60 (3) ◽  
pp. 727-749
Author(s):  
R E Taylor ◽  
John R Southon ◽  
Guaciara M Santos
Keyword(s):  
Mass Spectrometry ◽  
Accelerator Mass Spectrometry ◽  
Time Scale ◽  
Point Of View ◽  
General Validity ◽  
General Audience ◽  
Background Levels ◽  
Age Determinations

ABSTRACTWe consider one misconception of those who currently reject the general validity of radiocarbon (14C) age determinations older than, at most, 10,000 BP. There is an allegation that the presence of 14C reported by accelerator mass spectrometry (AMS) laboratories in their measurements of 14C infinite age (>100,000 years) organics used to define background levels, support their point of view. This article has been written for a general audience, primarily for those who have questions about the validity of these arguments. However, they may not be familiar with the literature relevant to providing a clear response to the claims of these individuals. We conclude that, in our view, of all of the possible explanations for the reports of the presence of 14C in these background samples, the least probable explanation has been advanced by those rejecting the validity of the 14C time scale in excess of, at most, 10,000 BP.

scholarly journals Radiocarbon Sample Preparation at the Circe AMS Laboratory in Caserta, Italy

Radiocarbon ◽  
2007 ◽  
Vol 49 (2) ◽  
pp. 225-232 ◽  
Author(s):  
Isabella Passariello ◽  
Fabio Marzaioli ◽  
Carmine Lubritto ◽  
Mauro Rubino ◽  
Antonio D'Onofrio ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Sample Preparation ◽  
Accelerator Mass Spectrometry ◽  
Isotope Fractionation ◽  
Background Levels

A system with several lines for the preparation of graphite targets for radiocarbon analysis has been built at the new accelerator mass spectrometry (AMS) facility in Caserta, Italy. Special attention has been paid in the design to the reduction of background contamination during sample preparation. Here, we describe the main characteristics of these preparation lines. Results of tests performed to measure 14C background levels and isotope fractionation in several blank samples with the Caserta AMS system are presented and discussed.

scholarly journals A Protocol for Radiocarbon Dating Tropical Subfossil Cave Guano

Radiocarbon ◽  
2009 ◽  
Vol 51 (3) ◽  
pp. 977-986 ◽  
Author(s):  
Christopher M Wurster ◽  
Michael I Bird ◽  
Ian Bull ◽  
Charlotte Bryant ◽  
Philippa Ascough
Keyword(s):  
Mass Spectrometry ◽  
Southeast Asia ◽  
Accelerator Mass Spectrometry ◽  
Radiocarbon Dating ◽  
Saturated Hydrocarbon ◽  
Lipid Fraction ◽  
Bulk Sample ◽  
Radiocarbon Dates ◽  
Organic Fractions ◽  
Age Determinations

We present accelerator mass spectrometry (AMS) radiocarbon dates on several organic fractions isolated from tropical guano deposits recovered from insular Southeast Asia. Differences were observed between 14C measurements made on bulk guano as well as bulk lipids, the saturated hydrocarbon fraction, solvent-extracted guano, and insect cuticles extracted from the same bulk sample. We infer that 14C dates from the bulk lipid fraction and saturated hydrocarbon fractions can be variably contaminated by exogenous carbon. In contrast, 14C measurements on solvent-extracted guano and isolated insect cuticles appear to yield the most robust age determinations.

scholarly journals Counting Statistics and Ion Interval Density in AMS

Radiocarbon ◽  
2004 ◽  
Vol 46 (3) ◽  
pp. 1103-1109 ◽  
Author(s):  
John S Vogel ◽  
Ted Ognibene ◽  
Magnus Palmblad ◽  
Paula Reimer
Keyword(s):  
Mass Spectrometry ◽  
Accelerator Mass Spectrometry ◽  
Temporal Distribution ◽  
Counting Statistics ◽  
Random Nature ◽  
Radiocarbon Calibration ◽  
Age Determinations

Confidence in the precisions of accelerator mass spectrometry (AMS) and decay measurements must be comparable for the application of the radiocarbon calibration to age determinations using both technologies. We confirmed the random nature of the temporal distribution of 14C ions in an AMS spectrometer for a number of sample counting rates and properties of the sputtering process. The temporal distribution of ion counts was also measured to confirm the applicability of traditional counting statistics.

scholarly journals Accelerator Mass Spectrometry at Arizona: Geochronology of the Climatic Record and Connections with the Ocean

2002 ◽  
Vol 2 ◽  
pp. 1579-1593 ◽  
Author(s):  
J.T. Jull ◽  
G.S. Burr ◽  
J.W. Beck ◽  
D.J. Donahue ◽  
D. Biddulph ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Radioactive Waste ◽  
Environmental Conditions ◽  
Accelerator Mass Spectrometry ◽  
Time Scale ◽  
Southern Oscillation ◽  
Waste Dump ◽  
Short Term ◽  
Millennial Time Scale ◽  
Climatic Record

There are many diverse uses of accelerator mass spectrometry (AMS).14C studies at our laboratory include much research related to paleoclimate, with14C as a tracer of past changes in environmental conditions as observed in corals, marine sediments, and many terrestrial records. Terrestrial records can also show the influence of oceanic oscillations, whether they are short term, such as ENSO (El Niño/Southern Oscillation), or on the millennial time scale. In tracer applications, we have developed the use of129I as well as14C as tracers for nuclear pollution studies around radioactive waste dump sites, in collaboration with IAEA. We discuss some applications carried out in Tucson, AZ, for several of these fields and hope to give some idea of the breadth of these studies.

scholarly journals Marine Turtle Bones from an Archaeological Site in Polynesia Yield Reliable Age Determinations

Radiocarbon ◽  
1990 ◽  
Vol 32 (2) ◽  
pp. 143-147 ◽  
Author(s):  
T S Dye
Keyword(s):  
Mass Spectrometry ◽  
Sample Size ◽  
Accelerator Mass Spectrometry ◽  
South Pacific ◽  
Archaeological Site ◽  
Marine Turtle ◽  
Long Distance ◽  
Marine Turtles ◽  
Ams Dating ◽  
Age Determinations

Accelerator mass spectrometry dating of three 50g samples of marine turtle bone from the basal cultural stratum of the Tongoleleka archaeological site, Lifuka Island, Kingdom of Tonga, South Pacific yields results that agree with conventional 14C dates on marine shell. A method for calibrating these dates that takes into account the long distance migrations of marine turtles in the South Pacific is proposed. A sample size greater than 50g is recommended for routine AMS dating of marine turtle bone.

scholarly journals New 14C Dates for the Early Natufian of El-Wad Terrace, Mount Carmel, Israel

Radiocarbon ◽  
2012 ◽  
Vol 54 (3-4) ◽  
pp. 813-822 ◽  
Author(s):  
Mina Weinstein-Evron ◽  
Reuven Yeshurun ◽  
Daniel Kaufman ◽  
Eileen Eckmeier ◽  
Elisabetta Boaretto
Keyword(s):  
Mass Spectrometry ◽  
Accelerator Mass Spectrometry ◽  
Southern Levant ◽  
Radiocarbon Age ◽  
Cultural Affiliation ◽  
The Core ◽  
Integral Role ◽  
First Results ◽  
Age Determinations ◽  
Good Agreement

The Natufian culture of the southern Levant played an integral role in the transition from simple huntergatherers to food-producing societies of the Neolithic, but the major Natufian hamlets are currently poorly dated. Moreover, none of these complex, continuously occupied base camps have delivered an adequate number of dates to enable an in-depth delineation of intra-Natufian developments. This paper presents the first results of our dating program at el-Wad terrace, Mount Carmel (Israel), one of the major Natufian hamlets of the “core area” of this culture. Thirteen accelerator mass spectrometry (AMS) radiocarbon age determinations were obtained from 46 bone (both ungulate and human) and charcoal samples, originating in Early Natufian living surfaces, dwellings, and burials. The obtained dates are largely in agreement with the cultural affiliation of the samples (13–15 kyr cal BP). Two series of dates from different locations show good agreement with the stratigraphy. The ages of the burials clearly point to their being younger than the living surfaces seemingly associated with them. Presently, no burials may be linked with the major architectural phase of Early Natufian el-Wad. Our ongoing dating program and the processing of additional samples from refined contexts will help shed important light on the initial phases of the Natufian culture, habitation duration, intensity, and continuity, as well as the relationships between site features and stratigraphy.

Dating Egypt's oldest ‘art’: AMS 14C age determinations of rock varnishes covering petroglyphs at El-Hosh (Upper Egypt)

Antiquity ◽  
2001 ◽  
Vol 75 (287) ◽  
pp. 68-72 ◽  
Author(s):  
D. Huyge ◽  
A. Watchman ◽  
M. De Dapper ◽  
E. Marchi
Keyword(s):  
Mass Spectrometry ◽  
Accelerator Mass Spectrometry ◽  
Rock Art ◽  
Nile Valley ◽  
Upper Egypt ◽  
14C Age ◽  
Age Determinations

Direct dating, using the Accelerator Mass Spectrometry (AMS) 14C method, indicates that some petroglyphs (rock art) at El-Hosh in Upper Egypt pre-date the early 7th millennium BP (mid 6th millennium cal BC), making it the oldest graphic activity recorded in the Nile Valley.

AMS 14C age determinations of Rapanui (Easter Island) wood sculpture: moai kavakava ET 48.63 from Brussels

Antiquity ◽  
2001 ◽  
Vol 75 (289) ◽  
pp. 529-532
Author(s):  
F. Forment ◽  
D. Huyge ◽  
H. Valladas
Keyword(s):  
Mass Spectrometry ◽  
Accelerator Mass Spectrometry ◽  
Easter Island ◽  
Raw Material ◽  
14C Age ◽  
Wood Sculpture ◽  
Age Determinations

Direct dating, using the Accelerator Mass Spectrometry (AMS) 14C method, of a wooden moai kavakava (anthropomorphic woodcarving) in the collection of the Royal Museums of Art and History in Brussels has given a date of about cal AD 1390–1480. As there are reasons to believe that this age not only regards the raw material but also the carving itself, preserved examples of Easter Island wood sculpture may be much older than previously assumed and possibly contemporaneous with the giant monolithic sculpture of the first half of the 2nd millennium AD.

scholarly journals Chronology of Late Pleistocene Humans in Eurasia: Results and Perspectives

Radiocarbon ◽  
2012 ◽  
Vol 54 (3-4) ◽  
pp. 339-350 ◽  
Author(s):  
Susan G Keates ◽  
Yaroslav V Kuzmin ◽  
George S Burr
Keyword(s):  
Mass Spectrometry ◽  
Eastern Europe ◽  
Late Pleistocene ◽  
Accelerator Mass Spectrometry ◽  
Human Remains ◽  
Modern Humans ◽  
Urgent Task ◽  
Human Fossils ◽  
Age Determinations

A compilation of direct age determinations for Late Pleistocene human fossils in eastern Europe and Asia is presented in this paper, and current problems with the dating of hominids in these regions are discussed. Only 25 human finds (4 Neanderthals and 21 modern humans) have been directly dated from Pleistocene eastern Europe and Asia. Indirect dating of human remains (using presumably associated organics) often is insecure, especially when information about the exact provenance of human fossils is lacking. Continuation of direct dating of Late Pleistocene humans in Eurasia, primarily with the help of the accelerator mass spectrometry (AMS) 14C method, is therefore an urgent task.

scholarly journals AMS Radiocarbon Measurements from the Swedish Varved Clays

Radiocarbon ◽  
2000 ◽  
Vol 42 (3) ◽  
pp. 323-333 ◽  
Author(s):  
Barbara Wohlfarth ◽  
Göran Possnert
Keyword(s):  
Mass Spectrometry ◽  
Accelerator Mass Spectrometry ◽  
Time Scale ◽  
Late Glacial ◽  
Plant Macrofossils ◽  
Northern Sweden ◽  
The Baltic Sea ◽  
Varve Chronology ◽  
Scandinavian Ice Sheet ◽  
The Baltic

The Swedish varve chronology, or Swedish Time Scale, is an annual chronology based upon the successive correlation of more than 1000 varve-thickness diagrams. The Late Glacial-Early Holocene varved clays were deposited as glaciolacustrine sediments in the Baltic Sea during the recession of the Scandinavian ice sheet. Formation of varved clays continued throughout the Holocene and is still going on in the estuary of River ångermanälven in northern Sweden. Accelerator mass spectrometry (AMS) radiocarbon measurements, which have been performed on terrestrial plant macrofossils extracted from the varved clays, show—in comparison with other annual chronologies—that several hundreds of varve years are missing in the varve chronology. These findings are supported by, among others, pollen stratigraphic investigations on time-equivalent varve year intervals. If an effort were undertaken to evaluate the erroneous parts, the Swedish Time Scale would have the potential of becoming a continuous annual chronology.

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