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ABSTRACT As part of the ongoing effort to improve the Northern Hemisphere radiocarbon ( 14 C) calibration curve, this study investigates the period of 856 BC to 626 BC (2805–2575 yr BP) with a total of 403 single-year 14 C measurements. In this age range, IntCal13 was constructed largely from German and Irish oak as well as Californian bristlecone pine 14 C dates, with most samples measured with a 10-yr resolution. The new data presented here is the first atmospheric 14 C single-year record of the older end of the Hallstatt plateau based on an absolutely dated tree-ring chronology. The data helped reveal a major solar proton event (SPE) which caused a spike in the production rate of cosmogenic radionuclides around 2610/2609 BP. This production event is thought to have reached a magnitude similar to the 774/775 AD production event but has remained undetected due to averaging effects in the decadal calibration data. The record leading up to the 2610/2609 BP event reveals a 11-yr solar cycle with varying cyclicity. Features of the new data and the benefits of higher resolution calibration are discussed.
Fahrni et al. (Mon,) studied this question.