Validity of Ams Dates on Maize from the Tehuacán Valley: A Comment on Macneish and Eubanks

2001 ◽  
Vol 12 (1) ◽  
pp. 87-90 ◽  
Author(s):  
Austin Long ◽  
Gayle J. Fritz
Keyword(s):  
Radiocarbon Dating ◽  
Wood Charcoal ◽  
Individual Plant ◽  
Tehuacán Valley ◽  
Radiocarbon Dates ◽  
Rock Shelter ◽  
Ams Radiocarbon Dating ◽  
Tehuacan Valley ◽  
Ams Dates ◽  
Plant Specimen

MacNeish and Eubanks (2000) reject the AMS radiocarbon dates on maize from the Tehuacán Valley, claiming that the specimens were contaminated with a substance called Bedacryl. We do not believe that the dated fragments were contaminated, and we review the processes by which they were selected and analyzed. We also describe Bedacryl and conclude that, had it been present as a contaminant, the resulting 14C ages should have been older rather than younger than expected. Considered along with recent AMS dates on cultigens from Tamaulipas, it seems evident that post-depositional disturbances in rock-shelter sites sometimes caused mixing of older and younger objects. Direct AMS radiocarbon dating is currently the best and least destructive way to determine whether or not an individual plant specimen is the same age as seemingly associated wood charcoal.

scholarly journals New AMS Radiocarbon Ages from the Preceramic Levels of Coxcatlan Cave, Puebla, Mexico: A Pleistocene Occupation of the Tehuacan Valley?

2021 ◽  
pp. 1-15
Author(s):  
Andrew D. Somerville ◽  
Isabel Casar ◽  
Joaquín Arroyo-Cabrales
Keyword(s):  
Mass Spectrometry ◽  
Last Glacial Maximum ◽  
Food Production ◽  
Tehuacán Valley ◽  
Rock Shelter ◽  
Last Glacial ◽  
Tehuacan Valley ◽  
Peopling Of The Americas ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Archaeological studies at Coxcatlan Cave in the Tehuacan Valley of southern Puebla, Mexico, have been instrumental to the development of the chronology for the region and for our understanding of the origins of food production in the Americas. This article refines the Preceramic chronology of the Tehuacan Valley by presenting 14 new accelerated mass spectrometry (AMS) radiocarbon ages from faunal bone samples uncovered from early depositional levels of the rock shelter. Although bones associated with the El Riego (9893–7838 cal BP), Coxcatlan (7838–6375 cal BP), and Abejas (6375–4545 cal BP) phase zones of the cave yielded ages similar to those of the previously proposed chronology for the region, bones from the Ajuereado phase zones at the base of the cave yielded surprisingly old ages that range from 33,448 to 28,279 cal BP, a time prior to the Last Glacial Maximum. Because these early ages are many thousands of years older than current models estimate for the peopling of the Americas, they require reassessments of the artifacts and ecofacts excavated from these early zones.

Testing the Accuracy of 14C Age Data from Pollen Concentrates in the Yangtze Delta, China

Radiocarbon ◽  
2014 ◽  
Vol 56 (1) ◽  
pp. 181-187 ◽  
Author(s):  
Chunhai Li ◽  
Yongxiang Li ◽  
George S Burr
Keyword(s):  
Radiocarbon Dating ◽  
Liquid Scintillation ◽  
Scintillation Counting ◽  
Yangtze Delta ◽  
Plant Materials ◽  
Radiocarbon Dates ◽  
Ams Radiocarbon Dating ◽  
14C Age ◽  
Climate Events ◽  
Age Determinations

In order to test the accuracy of accelerator mass spectrometry (AMS) radiocarbon dating of pollen, 8 samples of pollen concentrates and 4 bulk organic samples were collected and analyzed from trench T1041 at the Tianluoshan site, Yuyao city, Zhejiang Province. This site was chosen because a reliable chronology had been previously established there based on radiocarbon dates of plant materials. The pollen concentrate samples were measured using AMS 14C and the 4 bulk organic samples were measured by liquid scintillation counting (LSC). The pollen concentrates and bulk organic samples yield ages that are a few hundred years to thousands of years older than those from plant materials, respectively. Contributions from reworked sediments can explain the older ages for the pollen concentrates and sediment organic dates. This study suggests that caution must be exercised when discussing millennial- or centennial-scale climate events based on chronologies that are controlled by age determinations of pollen concentrates.

AMS Radiocarbon Dating of Lake Michigan Beach-Ridge and Dune Development

1997 ◽  
Vol 48 (1) ◽  
pp. 137-140 ◽  
Author(s):  
John Lichter
Keyword(s):  
Radiocarbon Dating ◽  
Lake Level ◽  
Sand Dune ◽  
Lake Michigan ◽  
Beach Ridge ◽  
Radiocarbon Dates ◽  
Beach Ridges ◽  
Ams Radiocarbon Dating ◽  
Climate Fluctuations ◽  
Radiocarbon Chronology

Strandplains of shore-parallel beach ridges bordering the Great Lakes are valuable for reconstructing histories of climate-related lake-level fluctuations. However, imprecise radiocarbon dates of ridge formation have frustrated development of dependable chronologies from which information about variation in the frequency of ridge formation and inferred climate fluctuations can be obtained. The resolution and precision of radiocarbon chronologies can be improved with AMS 14C dates of roots and rhizomes of plant species associated with the formation and growth of the sand-dune caps of breach ridges. These dates reliably estimate the timing of shore progradation when the base of the previously established beach ridge becomes inundated by the water table. An AMS radiocarbon chronology of beach-ridge formation in northern Lake Michigan shows that information about variation in the frequency of ridge formation is important for paleoclimatic interpretation.

scholarly journals A Pretreatment Procedure for the AMS Radiocarbon Dating of Sub-Fossil Insect Remains

Radiocarbon ◽  
2004 ◽  
Vol 46 (1) ◽  
pp. 147-154 ◽  
Author(s):  
J A Tripp ◽  
T F G Higham ◽  
R E M Hedges
Keyword(s):  
Mass Spectrometry ◽  
Radiocarbon Dating ◽  
The Other ◽  
Roman Britain ◽  
Ams Radiocarbon Dating ◽  
Maillard Reactions ◽  
Fossil Insect ◽  
Ams Dating ◽  
Acid Wash ◽  
Ams Dates

Two pretreatment methods for accelerator mass spectrometry (AMS) dating of insect remains were explored. One method involves a simple acid wash that removes carbonate, while the other is based on the industrial purification of chitin and results in isolation of polymeric chitosan. No contamination is observed from Maillard reactions during the deacetylation reaction used to isolate the chitosan. The methods were tested on Coleoptera samples from two Roman Britain sites. Our results demonstrate that both methods produce acceptable AMS dates that correspond well to the expected age of the deposits from which they came.

scholarly journals Isotopic Fractionation of Norwegian Materials for Radiocarbon Dating

Radiocarbon ◽  
1980 ◽  
Vol 22 (3) ◽  
pp. 980-986 ◽  
Author(s):  
Steinar Gulliksen
Keyword(s):  
Standard Error ◽  
Radiocarbon Dating ◽  
Isotopic Fractionation ◽  
Wood Charcoal ◽  
Bone Collagen ◽  
Standard Errors ◽  
Radiocarbon Dates ◽  
Bone Material ◽  
Mean Values ◽  
C Value

To improve reporting of radiocarbon dates, Stuiver and Polach (1977) recommend that reported standard errors should include the error in the applied δ13C value, and suggest estimated mean values for δ13C to be applied when not measured. Based on δ13C data for ca 250 samples measured during 1975-1979, mean values for different materials dated by the Trondheim radiocarbon laboratory have been compiled. All material is from Norway and Svalbard (marine bone collagen). For peat, gyttja, and terrestrial bone material, δ13C should be measured to obtain optimal precision in the dates. For shell, wood, charcoal, and marine bones, the standard error in an estimated δ13C value will only increase uncertainty of a date from ±50 years to ca ±55 years.

scholarly journals AMS Radiocarbon Dates of Kurgans Located On the Ust'-Yurt Plateau, Uzbekistan

Radiocarbon ◽  
2005 ◽  
Vol 47 (2) ◽  
pp. 235-241 ◽  
Author(s):  
Soren Blau ◽  
Vadim Yagodin
Keyword(s):  
Mass Spectrometry ◽  
Accelerator Mass Spectrometry ◽  
Radiocarbon Dating ◽  
Skeletal Remains ◽  
Archaeological Sites ◽  
Late Prehistoric ◽  
Human Skeletal Remains ◽  
Radiocarbon Dates ◽  
Relative Dating ◽  
Ams Dates

Recent osteological analyses of archaeological human skeletal remains from the Ust'-Yurt Plateau, Uzbekistan, provided the opportunity to obtain samples for radiocarbon dating. The results of 18 accelerator mass spectrometry (AMS) dates are presented in this paper and provide the first absolute dates for late prehistoric and early historic archaeological sites in Uzbekistan. The AMS dates suggest that most sites are earlier than have been traditionally thought based on relative dating using artifact typologies.

AMS Dates of New Maize Specimens Found in Rock Shelters of the Tehuacan Valley

Radiocarbon ◽  
2018 ◽  
Vol 60 (3) ◽  
pp. 975-987
Author(s):  
Esperanza Torres-Rodríguez ◽  
Miguel Vallebueno-Estrada ◽  
Javier Martínez González ◽  
Angel García Cook ◽  
Rafael Montiel ◽  
...  
Keyword(s):  
Archaeological Sites ◽  
American Continent ◽  
Large Collection ◽  
Tehuacán Valley ◽  
Global Comparison ◽  
Tehuacan Valley ◽  
San Marcos ◽  
Southeastern Region ◽  
Ams Dates ◽  
Rock Shelters

ABSTRACTA large collection of maize macro-specimens has been gathered from archaeological sites across the American continent, but only a few have been directly dated by accelerator mass spectrometry (AMS). We recently conducted two new excavations in several rock shelters of Tehuacán valley (San Marcos, Coxcatlán, and Purrón) and uncovered 132 non-manipulated macro-specimens of maize suitable for morphological and paleogenomic analysis, including many complete cobs, stalks, internodes, and leaves. Direct AMS dates for 43 samples found in San Marcos or Coxcatlán confirm the previously reported chronologies for these sites. By contrast, a cob found in Purrón was dated to 3060±30 before present (3360–3180 cal BP) (2σ), demonstrating that maize was present at that site at least 1500 calendar years earlier than previously expected, and suggesting that other specimens of similar age are still likely to be found in the southeastern region of the Tehuacán valley. A global comparison of macro-specimen chronology across the continent shows that the current archaebotanical record does not yet reflect the chronology of dispersal from central Mexico to northern or southern regions, opening the possibility for finding the missing links in subsequent expeditions within Mexico and Central America.

scholarly journals Too Old AMS Radiocarbon Dates Obtained from Moss Remains from Lake Kwiecko Bottom Sediments (N Poland)

2008 ◽  
Vol 32 (-1) ◽  
pp. 13-19 ◽  
Author(s):  
Jacek Madeja ◽  
Dariusz Latowski
Keyword(s):  
Bottom Sediments ◽  
Pollen Analysis ◽  
Radiocarbon Dating ◽  
Radiocarbon Dates ◽  
Ams Radiocarbon Dating ◽  
Palynological Data

Too Old AMS Radiocarbon Dates Obtained from Moss Remains from Lake Kwiecko Bottom Sediments (N Poland)The paper presents the results of the AMS radiocarbon dating of moss macrofossils which seem to be too old in the context of palynological data. The lack of agreement between the obtained results of radiocarbon dating and pollen analysis has been discussed. Some possible causes of the discrepancies between the results of radiocarbon dating and palynological dating have been given.

scholarly journals Radiocarbon Dating of the Decorated Cosquer Cave (France)

Radiocarbon ◽  
2016 ◽  
Vol 59 (2) ◽  
pp. 621-633 ◽  
Author(s):  
H Valladas ◽  
A Quiles ◽  
M Delque-Kolic ◽  
E Kaltnecker ◽  
C Moreau ◽  
...  
Keyword(s):  
Deep Water ◽  
Radiocarbon Dating ◽  
Soil Surface ◽  
Wood Charcoal ◽  
Radiocarbon Dates

AbstractThe Grotte Cosquer (southeastern France) is a Paleolithic painted cave only accessible by a deep-water dive. The cave has yielded numerous Paleolithic engravings and drawings, which were produced from wood charcoal. This article presents new radiocarbon dates obtained on samples collected in 2012 directly on 17 parietal representations and at the soil surface, and discusses the 14C results obtained since the discovery of the cave in 1992. A total of 41 samples were dated with ages ranging from 33,000 to 20,000 cal BP. They show that the cave was intermittently decorated over about 10,000 yr.

AMS Radiocarbon Dates of Pyroclastic-Flow Deposits on the Southern Slope of the Kuju Volcanic Group, Kyushu, Japan

Radiocarbon ◽  
2016 ◽  
Vol 59 (2) ◽  
pp. 483-488 ◽  
Author(s):  
Mitsuru Okuno ◽  
Shinji Nagaoka ◽  
Yoko Saito-Kokubu ◽  
Toshio Nakamura ◽  
Tetsuo Kobayashi
Keyword(s):  
Mass Spectrometry ◽  
Pyroclastic Flow ◽  
Accelerator Mass Spectrometry ◽  
Radiocarbon Dating ◽  
Southern Slope ◽  
Radiocarbon Dates ◽  
Ams Radiocarbon Dating ◽  
Volcanic Group ◽  
Lava Domes ◽  
History Of

AbstractThe Kuju volcanic group, located in central Kyushu, Japan, consists of small stratovolcanoes and lava domes. To refine the eruptive history of the group, we conducted accelerator mass spectrometry (AMS) radiocarbon dating of charcoal fragments from three pyroclastic-flow (PF) deposits on the southern slope. The obtained 14C dates are consistent with the geomorphology, stratigraphy, and thermoluminescence (TL) ages. The Handa PF deposits, which are products of the largest eruption of the group, were dated to ~53.5 ka BP. The Shirani and Muro PF deposits, which are block-and-ash flows, were dated to 44 to >50 cal ka BP and 35–39 cal ka BP, respectively. These ages can be correlated with TL ages for lava domes. This study demonstrates that the lava domes and associated PF deposits formed after the Handa eruption.

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