Publications by authors named "Carol Griggs"

5 Publications

  • Page 1 of 1

Mediterranean radiocarbon offsets and calendar dates for prehistory.

Sci Adv 2020 Mar 18;6(12):eaaz1096. Epub 2020 Mar 18.

Center for Applied Isotope Studies, University of Georgia, 120 Riverbend Rd., Athens, GA 30602, USA.

A single Northern Hemisphere calibration curve has formed the basis of radiocarbon dating in Europe and the Mediterranean for five decades, setting the time frame for prehistory. However, as measurement precision increases, there is mounting evidence for some small but substantive regional (partly growing season) offsets in same-year radiocarbon levels. Controlling for interlaboratory variation, we compare radiocarbon data from Europe and the Mediterranean in the second to earlier first millennia BCE. Consistent with recent findings in the second millennium CE, these data suggest that some small, but critical, periods of variation for Mediterranean radiocarbon levels exist, especially associated with major reversals or plateaus in the atmospheric radiocarbon record. At high precision, these variations potentially affect calendar dates for prehistory by up to a few decades, including, for example, Egyptian history and the much-debated Thera/Santorini volcanic eruption.
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http://dx.doi.org/10.1126/sciadv.aaz1096DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7080444PMC
March 2020

Radiocarbon re-dating of contact-era Iroquoian history in northeastern North America.

Sci Adv 2018 Dec 5;4(12):eaav0280. Epub 2018 Dec 5.

University of Vienna, VERA Laboratory, Faculty of Physics, Isotope Research and Nuclear Physics, Währinger Straße 17, A-1090 Vienna, Austria.

A time frame for late Iroquoian prehistory is firmly established on the basis of the presence/absence of European trade goods and other archeological indicators. However, independent dating evidence is lacking. We use 86 radiocarbon measurements to test and (re)define existing chronological understanding. Warminster, often associated with Cahiagué visited by S. de Champlain in 1615-1616 CE, yields a compatible radiocarbon-based age. However, a well-known late prehistoric site sequence in southern Ontario, Draper-Spang-Mantle, usually dated ~1450-1550, yields much later radiocarbon-based dates of ~1530-1615. The revised time frame dramatically rewrites 16th-century contact-era history in this region. Key processes of violent conflict, community coalescence, and the introduction of European goods all happened much later and more rapidly than previously assumed. Our results suggest the need to reconsider current understandings of contact-era dynamics across northeastern North America.
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http://dx.doi.org/10.1126/sciadv.aav0280DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6281431PMC
December 2018

Fluctuating radiocarbon offsets observed in the southern Levant and implications for archaeological chronology debates.

Proc Natl Acad Sci U S A 2018 06 29;115(24):6141-6146. Epub 2018 May 29.

University of Arizona Accelerator Mass Spectrometry Laboratory, University of Arizona, Tucson, AZ 85721.

Considerable work has gone into developing high-precision radiocarbon (C) chronologies for the southern Levant region during the Late Bronze to Iron Age/early Biblical periods (∼1200-600 BC), but there has been little consideration whether the current standard Northern Hemisphere C calibration curve (IntCal13) is appropriate for this region. We measured C ages of calendar-dated tree rings from AD 1610 to 1940 from southern Jordan to investigate contemporary C levels and to compare these with IntCal13. Our data reveal an average offset of ∼19 C years, but, more interestingly, this offset seems to vary in importance through time. While relatively small, such an offset has substantial relevance to high-resolution C chronologies for the southern Levant, both archaeological and paleoenvironmental. For example, reconsidering two published studies, we find differences, on average, of 60% between the 95.4% probability ranges determined from IntCal13 versus those approximately allowing for the observed offset pattern. Such differences affect, and even potentially undermine, several current archaeological and historical positions and controversies.
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http://dx.doi.org/10.1073/pnas.1719420115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6004441PMC
June 2018

Integrated Tree-Ring-Radiocarbon High-Resolution Timeframe to Resolve Earlier Second Millennium BCE Mesopotamian Chronology.

PLoS One 2016 13;11(7):e0157144. Epub 2016 Jul 13.

University of Vienna, VERA Laboratory, Faculty of Physics, Isotope Research and Nuclear Physics, Währinger Straße 17, A-1090 Vienna, Austria.

500 years of ancient Near Eastern history from the earlier second millennium BCE, including such pivotal figures as Hammurabi of Babylon, Šamši-Adad I (who conquered Aššur) and Zimrilim of Mari, has long floated in calendar time subject to rival chronological schemes up to 150+ years apart. Texts preserved on clay tablets provide much information, including some astronomical references, but despite 100+ years of scholarly effort, chronological resolution has proved impossible. Documents linked with specific Assyrian officials and rulers have been found and associated with archaeological wood samples at Kültepe and Acemhöyük in Turkey, and offer the potential to resolve this long-running problem. Here we show that previous work using tree-ring dating to place these timbers in absolute time has fundamental problems with key dendrochronological crossdates due to small sample numbers in overlapping years and insufficient critical assessment. To address, we have integrated secure dendrochronological sequences directly with radiocarbon (14C) measurements to achieve tightly resolved absolute (calendar) chronological associations and identify the secure links of this tree-ring chronology with the archaeological-historical evidence. The revised tree-ring-sequenced 14C time-series for Kültepe and Acemhöyük is compatible only with the so-called Middle Chronology and not with the rival High, Low or New Chronologies. This finding provides a robust resolution to a century of uncertainty in Mesopotamian chronology and scholarship, and a secure basis for construction of a coherent timeframe and history across the Near East and East Mediterranean in the earlier second millennium BCE. Our re-dating also affects an unusual tree-ring growth anomaly in wood from Porsuk, Turkey, previously tentatively associated with the Minoan eruption of the Santorini volcano. This tree-ring growth anomaly is now directly dated ~1681-1673 BCE (68.2% highest posterior density range), ~20 years earlier than previous assessments, indicating that it likely has no association with the subsequent Santorini volcanic eruption.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0157144PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4943651PMC
July 2017

Old World megadroughts and pluvials during the Common Era.

Sci Adv 2015 Nov 6;1(10):e1500561. Epub 2015 Nov 6.

Ecoclimatology, Technische Universität München, Freising 85354, Germany.

Climate model projections suggest widespread drying in the Mediterranean Basin and wetting in Fennoscandia in the coming decades largely as a consequence of greenhouse gas forcing of climate. To place these and other "Old World" climate projections into historical perspective based on more complete estimates of natural hydroclimatic variability, we have developed the "Old World Drought Atlas" (OWDA), a set of year-to-year maps of tree-ring reconstructed summer wetness and dryness over Europe and the Mediterranean Basin during the Common Era. The OWDA matches historical accounts of severe drought and wetness with a spatial completeness not previously available. In addition, megadroughts reconstructed over north-central Europe in the 11th and mid-15th centuries reinforce other evidence from North America and Asia that droughts were more severe, extensive, and prolonged over Northern Hemisphere land areas before the 20th century, with an inadequate understanding of their causes. The OWDA provides new data to determine the causes of Old World drought and wetness and attribute past climate variability to forced and/or internal variability.
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http://dx.doi.org/10.1126/sciadv.1500561DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4640589PMC
November 2015