High-Precision ¹⁴C Measurement of Irish Oaks to Show the Natural Atmospheric ¹⁴C Variations of the AD Time Period

Abstract

The high-precision 14C measurement of bi-decade and decade samples of Irish Oak for the time period AD 50 to 1830 is presented. The samples were taken from dendrochronologically dated Irish Oak providing an absolute chronology for this period. While the natural atmospheric 14C concentration shows cyclic deviations from a constant value, the amplitudes of such deviations vary considerably. Repeated measurement and interlaboratory checks justify a claim to accuracy in the data given. Comparison of a large number of data sets between Belfast and Seattle show that the different techniques of scintillation counting of 14C6H6 and gas counting of 14CO2 derived from different wood species grown in different continents give no significant bias. Thus, it is justifiable to use this data set as a high-precision calibration curve for the AD period. Over most of this period bi-decade samples were measured giving a slightly reduced resolution of short-term variation when compared to the measurement of decade intervals; however, any difference is not apparent when such curves are compared. It is of much greater importance that a comparison of data sets is without bias if a combined calibration curve is to have sufficient integrity for general use. Averaging the data from Belfast and Seattle would improve the validity of such an AD 14C calibration curve since it would tend to smooth out slight local variations and become internationally more acceptable.

Lake shoreline development, frost weathering and rock platform erosion in an alpine periglacial environment, Jotunheimen, southern Norway

“…The range of dates adopted for the onset of rock platform development (A.D. 1700 to A.D. 1750) is based primarily on the assumption that the advance of Boverbreen to its 'Little Ice Age' limit was, relatively, as rapid as that of the Jostedalsbreen outlet glaciers (see above). This is a reasonable assumption and justified to some extent by the 14C dating although the well known problems of calibrating such recent dates (Stuiver 1978(Stuiver , 1982Pearson & Baillie 1983) prevent precise dating based on the 14C evidence alone.…”

High-Precision 14C Measurement of German and Irish Oaks to Show the Natural 14C Variations from 7890 to 5000 BC

“…The techniques used for the combustion of sample carbon and its conversion to benzene have remained essentially the same in our new laboratory, although completely new, redesigned combustion and synthesis lines have been installed. The methods are detailed in previous publications (Pearson 1979(Pearson , 1980(Pearson , 1983Pearson & Baillie 1983;). The fundamental requirements for high-precision 14C measurement do not change; they are to measure only pure uncontaminated sample carbon under known stable and standardized counting conditions.…”

Aspects taphonomiques de la stratigraphie et de la datation de charbons de bois dans les sols : exemple de quelques sols des Alpes

“…Niveaux MAUR Pearson et al (1986) ± 70 BP) dans le niveau II, mesure effectuée sur trois petits fragments, et ± 4350 cal. BP (3885 ± 70 BP) dans le niveau IV.…”