C03_P01

Cosmogenic radionuclides at Law Dome, East Antarctica,

record the 774/5 AD and 993/4 AD Miyake Events.

Smith A¹, Curran M², Dee M⁴, Fink D¹, Kuitems M⁴, Levchenko V¹, Moy A², Scifo A⁴, Simon K¹, Wilcken K¹

¹ANSTO, Sydney, Australia, ²Australian Antarctic Division, Hobart, Australia, ³Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia, ⁴Centre for Isotope Research, University of Groningen, Gronigen, Netherlands

This project investigates increased atmospheric production of cosmogenic radionuclides in ice core records at Law Dome, East Antarctica, for three extreme events: the Carrington Event (CE) of 1859 AD and the Miyake Events (ME) of 774/5 AD and 993/4 AD. Ice samples for ¹⁰Be and ³⁶Cl analysis were taken from ice cores drilled near the summit of Law Dome, East Antarctica. This will be the first time these radionuclides have been measured at the same site for these events, allowing a direct comparison of ME774, ME993 and CE1859 under similar transport conditions.

A survey of ¹⁰Be at annual resolution spanning 30 years allowed an exact location of the events in the ice cores. We clearly identified the expected ME774 and ME993 ¹⁰Be peaks, which were ~ 4 years earlier and ~ 2 years earlier, respectively, than the layer-counted ice core chronology, but within the margin of error. No discernible ¹⁰Be peak or ³⁶Cl peak was found for CE1859 at annual resolution.

A further set of ¹⁰Be samples at bi-monthly resolution were taken over ME774 and ME993 to better define the fine structure and amplitude of the signal. These sub-annual results confirm the survey results, showing additional structure and higher ¹⁰Be concentrations. High resolution ¹⁴C analysis has already been undertaken at Groningen over all three events and will be reported at this meeting. Finally, we will be combining the mobile phases from the sub-annual and annual 10Be processing to yield sufficient sample for ³⁶Cl AMS analysis across these two Miyake Events.

C03_P02

The potential for using Δ¹⁴C excursions to accurately date floating pine chronologies from the Hallstatt period

Wiktorowski D¹, Rakowski A², Krapiec M¹, Pawlyta J¹, Barniak J¹, Szychowska-Krąpiec E¹

¹AGH, Kraków, Poland, ²SUT, Gliwice, Poland

In Central Europe, the dendrochronological method in absolute dating is widely used, but a significant difficulty in its application is the lack of pine (Pinus sylvestris) chronologies reaching back more than tenth century CE. Recently, long floating pine chronologies covering the last thousand years of the BCE were compiled at the Dendrochronological Laboratory of AGH University of Science and Technology in Krakow. These are mean curves developed from hundreds of trunks of subfossil trees found in Polish peatlands. They were preliminarily dated using the wiggle-matching method. Later, rapid Δ¹⁴C changes at 660 BCE and at 814-813 BCE were used for their precise dating with annual precision.

C03_P03

Variations in the radiocarbon calibration curves around known and suspected Δ¹⁴C excursions

Rakowski A¹, Pawlyta J², Krąpiec M², Huels M³, Molnar M⁴

¹SUT, Gliwice, Poland, ²AGH, Kraków, Poland, ³Uni Kiel, Kiel, Germany, ⁴ATOMKI, Debrecen, Hungary

The search for and analysis of rapid Δ¹⁴C changes in the past has received much attention in recent years. In this paper, we will present the results of searching for rapid Δ¹⁴C changes in the raw data used to build radiocarbon calibration curves: IntCa20 and SHCal20 and attempts to identify them in rings of single trees from Poland. We collected information on the periods of occurrence of rapid changes identified by other authors and within our own review of Δ¹⁴C variability in raw data of calibration curves. For some of the periods we found, we were able to find research material in the form of tree trunks from areas of Poland. We determined the concentration of ¹⁴C in tree rings. In this paper we present a comparison of the obtained Δ¹⁴C for our samples and raw data and the IntCal20 curve itself.