ACRA Webinar Invitation: A Focus on Bones
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Live Webinar: April 14, 2022
Presenters: Prof. James Watson (Arizona State Museum Associate Director) & Maren Pauly, PhD (Beta Analytic Scientific Associate)
Since the start of the industrial revolution, carbon dioxide (CO2) has been accumulating in the atmosphere as a result of human activities (e.g. combustion of fossil fuels and land use change) – with an increase of over 100ppm CO2 in the past 60 years alone.
Bones contaminated with polyvinyl acetate (PVA) require specialized pretreatment, such as solvent extractions, before radiocarbon dating. The success of the dating also varies if the bone has been soaked in PVA or if the PVA was applied in localized areas.
The remains of insects are dated using the exoskeleton made of chitin, which is a fibrous substance made up of polysaccharides. Given the very small size and weight of the exoskeletons, they have historically been very difficult to date.
There can be problems encountered when dating cores (organic sediment fraction) that have been stored for long periods of time depending on the storage conditions.
Beta Analytic invites members of the American Cultural Resources Association (ACRA) to join the Radiocarbon Dating Basics webinar scheduled on May 13, 2021, from 2:00 PM to 3:30 PM Eastern Time. Beta Analytic and Isobar Science account manager Dr. Maren Pauly is the speaker.
There have been different methods of measuring carbon-14 since Willard Libby pioneered the radiocarbon dating technique in the 1940s – from the radiometric techniques of gas proportional counting and liquid scintillation counting to the more recent accelerator mass spectrometry (AMS).
Rescue archaeology plays the role of surveying and recovering any valuable finds from various sites. In the time-pressured environment of rescue archaeology, swift assessments and excavations where necessary are critical. For finds where radiocarbon dating is needed, this can throw a spanner in the works as the time lost waiting for results can be costly for the developers.
For deep sea corals, a combination of radiocarbon dating and uranium-thorium dating can be used. The carbon-14 date represents the age of the coral and the water, whereas the uranium-thorium date reflects the coral itself. This can provide information on past deep sea circulation rates.
Radiocarbon dating otoliths has the potential to confirm both the absolute age of individual fish and annuli formation. Despite the many techniques that can be used for age validation, only radiocarbon dating can provide the absolute age in a variety of fishes particularly the long-lived ones.
Choosing a radiocarbon dating laboratory is not always easy; there are many factors to consider and often budgetary constraints to negotiate. An important factor in decision-making is how quickly the results are reported, particularly if there are deadlines to meet. Even when there is no impending deadline, a fast turnaround time can be important and lead to cost savings in the long run.
As part of its commitment to provide high-quality results to its clients, ISO/IEC 17025:2017-accredited Beta Analytic does not accept pharmaceutical samples with “tracer Carbon-14” or any other material containing artificial Carbon-14 (14C) to eliminate the risk of cross-contamination.
Researchers often ask which material is best for radiocarbon dating – bones or teeth. Based on our lab’s experience, either material can provide the best date. However, the environmental conditions for these materials should be taken into account during sample selection.
There are two possible reservoir corrections applied to a radiocarbon date for marine carbonates – the localized reservoir correction (Delta±R) and the global marine reservoir correction. The former is provided by the client to the lab before the analyses while the latter is part of the calibration program.
It is possible to date fired clay bricks, but it depends on how the bricks were manufactured and what types of contamination may have been absorbed into the bricks since they were put in place.
Just like sediment, it is better to date the macrofossils found in sand. In the absence of macrofossils, sand can be dated if there is an organic material on the surface of the sand. If there is enough carbon present in the organic coating, a radiocarbon date can be obtained.
What if there are several materials found in sediment (e.g. wood, charcoal, seeds) but each one does not meet the lab’s minimum sample size requirement, can a mixture of materials be dated?