Browsing Radiocarbon, Volume 51, Number 1 (2009) by Title
Now showing items 21-23 of 23
The Iron Age Around the Mediterranean: A High Chronology Perspective from the Groningen Radiocarbon DatabaseIn this paper, we present an overview of radiocarbon dating contributions from Groningen, concerning 9 sites from around the Mediterranean region: Israel, Sinai (Egypt), Jordan, Spain, Tunisia, and Italy. Full date lists of the 9 sites are presented. Our 14C dates are discussed in terms of present actual chronological debates. We show that all our 14C dates coherently support a "high chronology" for the Iron Age in each respective area of the Mediterranean region.
The Mysterious 14C DeclineFundamental to the field of radiocarbon dating is not only the establishment of the temporal record of the calendar age-radiocarbon age offsets but also the development of an understanding of their cause. Although part of the decline in the magnitude of this offset over the past 40,000 can be explained by a drop in 14C production rate associated with a progressive increase in the strength of the Earth's magnetic shielding, it is clear that changes in the distribution of 14C among the Earth's active carbon reservoirs are also required. In particular, the steep 15% decline in the 14C to C ratio in atmospheric CO2 and surface ocean CO2, which occurred in a 3 kyr-duration interval marking the onset of the last deglaciation, appears to require that a very large amount (at least 5000 gigatons) of 14C-deficient carbon was transferred to or within the ocean during this time interval. As no chemical or stable isotope anomaly associated with this injection appears in either the marine sediment or polar ice records, this injection must involve a transfer within the ocean (i.e. a mixing of 2 ocean reservoirs, one depleted in 14C and the other enriched in 14C). Although evidence for the existence of a salt-stabilized glacial-age abyssal ocean reservoir exists, a search based on benthic-planktic age differences and 13C measurements appears to place a limit on its size well below that required to account for the steep 14C decline.
The Radiocarbon Calibration from an Irish Oak PerspectiveBetween 1968 and 1984, a 7272-yr oak chronology was constructed in Belfast, Northern Ireland, in order to provide a local calibration of the radiocarbon timescale. This single-minded exercise in chronology construction provided an exciting occupation for a group of researchers that can be likened to a race in which there was no guarantee of a finish. The existence of a parallel dendrochronological enterprise in Germany added both competition and the possibility of independent replication. The initial completion of both chronologies by 1984, and respective calibrations by 1986, left an important legacy of 2 absolutely dated tree-ring chronologies for multifarious research purposes.