C05_P01

Radiocarbon analysis of annually published journals

Gautschi P¹, Brehm N¹, Wertnik M¹, Synal H¹, Wacker L¹

¹ETH Zurich, Zurich, Switzerland

The paper of books or journals is typically produced from cellulose extracted from trees. This makes them potentially suitable for radiocarbon dating. However, precise calendar age determination of the measured radiocarbon ages is difficult. Paper production has a lot of unknown factors such as different tree ages, i.e. number of tree rings, which go into the production of cellulose. Additionally, storage time between harvest of a tree and final publication is usually unknown and may vary. Therefore, the atmospheric integration time of a paper product, is an unknown distribution.

A series of 52 annually published journals over the ¹⁴C bomb pulse (1947 - 2021 AD) have been prepared for radiocarbon analysis to study the age assembly and the storage time of trees used for the paper. The measured ¹⁴C concentrations were compared to modelled ¹⁴C concentrations in paper, which are based on a simple tree-ring model and assuming the cellulose was formed from atmospheric CO₂ at the year of formation. Best agreements were obtained assuming a mean age of trees of 40 to 80 years and a relatively short storage time of two years between the harvest of trees and the final publication. Although the measured journals follow the model qualitatively, some significant deviations were observed between individual years of publication.

C05_P02

Barley Mash its history in the Radiocarbon Inter-comparison studies and its role as a modern carbon standard.

Naysmith P¹, Scott M², Dunbar E¹

¹SUERC, East Kilbride, United Kingdom, ²School of Mathematics and Statistics, University of Glasgow,

Over the past 30 years, the format of the radiocarbon (¹⁴C) inter-comparison studies has changed due to the change and development in measurement techniques. The selection of sample types used in these studies has remained constant—namely, natural and routinely dated materials that could subsequently be used as in-house laboratory standard material. Barley Mash, a by-product from the manufacture of malt whisky, is a good example of one of the widely used material from the Intercomparison studies.  Barley from a single year’s growing season is used in the production of whisky, often coming from a single geographical location and is available is large quantities, thus making it a suitable modern carbon reference material. Barley Mash samples have been used ten times in inter-comparison starting with TIRI, in 1992 through to GIRI, in 2021, with the same batch of barley mash being used in multiple inter-comparison studies. In this paper, the barley mash results from all the intercomparisons will be collated and reanalysed.

During the last 19 years, the Barley Mash TIRI A has been used in the SUERC ¹⁴C laboratory as an in-house laboratory standard material resulting in a dataset of several thousand of measurements. Such a rich data set is mined to illustrate some of the benefits arising from the inter-comparison program.

C05_P03

Determination of the influence of air parcels in the Northern and Southern Hemisphere on radiocarbon calibration in Southern America

Ancapichun S¹, Pawlyta J², Rakowski A³, Sieczkowska D⁴

¹Universidad de Concepción, Concepción, Chile, ²AGH, Kraków, Poland, ³SUT, Gliwice, Poland, ⁴University of Warsaw, Warsaw, Poland

The chronology of Machu Picchu was traditionally associated with the period attributed to the reign of Pachacuti Inca Yupanqui. Within the scheme of the so-called historical chronology, proposed by John H. Rowe in 1945, the ascension to power of Pachacuti Inca took place around 1438 CE and the construction of Machu Picchu began by 1450 -1460 CE. Several radiocarbon-dated samples may help to understand the chronology of the construction of llaqta of Machu Picchu, Chachabamba, and Choqesuysuy. However, there is a lack of consensus between different radiocarbon-based Inca chronologies, because of the lack of information of which calibration curves to use: Northern Hemisphere (NH), Southern Hemisphere (SH), or a mixed calibration curve? Thus, the main goal of the present investigation is to develop a new methodological approach to reconstruct a consistent radiocarbon-based Incan chronology, an approach based on the determination, through modeling, of the proportion of NH and SH air parcels arriving at three relevant Inca settlements. We found air parcels contributions from the NH and SH for: Machu Picchu (50% NH and 50% SH), Chamical (29% NH and 71% SH), and Tiquischullpa (41% NH and 59% SH). Thereby, our investigation brings three proportions to mix NH and SH 14C curves, based on an empirical method, for Inca’s radiocarbon dating studies. Our study emphasizes that great attention should be paid when applying radiocarbon calibration to radiocarbon measurements of samples originating in regions under the influence of the atmospheric circulation-boundary between hemispheres. 

C05_P04

Comprehensive update of marine reservoir values for New Zealand coastal waters to inform coastal hazard research

Turnbull J^1,2, Clark K¹, Ferrick T¹, Marshall B³, Howarth J⁴

¹GNS Science, Lower Hut, New Zealand, ²CIRES, University of Colorado, Boulder, USA, ³Te Papa Tongarewa Museum of New Zealand, Wellington, New Zealand, ⁴Victoria University of Wellington, Wellington, New Zealand

Accurate dating of coastal hazard events such as earthquakes and tsunamis typically hinges upon marine radiocarbon ages, and a well-constrained marine reservoir correction is vital to evaluating the size and frequency of large to great subduction earthquakes and tsunamis.     Yet in New Zealand, we have relied on only 31 ∆R values from four locations to estimate ∆R for the entire coastline.  Here we add 170 new measurements to the marine reservoir correction dataset for the mainland New Zealand and evaluated the influence of location, feeding method, living depth, environmental preference and species on the variance in ΔR values. We find there are no significant differences between ΔR values from suspension-feeding organisms compared to browsing/scavenger/carnivore-feeding organisms, and we find little variability between species that prefer estuarine environments to open coastal environments. This means that when dating shells from geological records, we do not need to take particular care to avoid certain species that may have anomalies of carbon precipitation in their shells.  Importantly, location is the dominant control on ∆R variability and we recommend the subdivision of New Zealand into five large regions, each with a different ΔR value.