Radiocarbon, Volume 48, Number 1 (2006)

Testing the Limits: Radiocarbon Dating and the End of the Late Bronze Age

Sun, 01 Jan 2006 00:00:00 GMT

Testing the Limits: Radiocarbon Dating and the End of the Late Bronze Age Hagens, Graham Archaeometry is becoming an increasingly important tool in chronological research related to events in the Ancient Near East during the 2nd millennium BCE. This paper is a review of recently published radiometric results in an attempt to establish the probable dating range for one particular event that occurred during the last quarter of that millennium, the end of the Late Bronze Age. The conclusion is that in spite of significant improvements in methodology in recent years, the quantity and quality of radiocarbon data are still insufficient to define the range of that date to much better than a century. It is concluded that the most likely date of the Late Bronze/Iron Age transition (here defined by the arrival of Mycenaean LH IIIC:1b pottery in the Levant) is somewhere in the 8-decade range between ~1170 to 1100 BCE. A comparative study of archaeological and historical evidence would appear to favor the lower value.

Southern Palestinian Chronology: Two Radiocarbon Dates for the Early Bronze Age at Tell El-Hesi (Israel)

Sun, 01 Jan 2006 00:00:00 GMT

Southern Palestinian Chronology: Two Radiocarbon Dates for the Early Bronze Age at Tell El-Hesi (Israel) Anderson, Roger W. Several articles reporting radiocarbon dates of Early Bronze Age (EB) material from excavations in the southern Levant have been published over the last 30 yr. The excavations conducted at Tell el-Hesi have produced material from which 2 additional 14C dates have been extracted to date. The 2 samples confirm the EB dating of Field VI material and suggest EB III settlement at Hesi might be earlier than previously reported based on pottery typology.

Seawater Radiocarbon Evolution in the Gulf of Alaska: 2002 Observations

Sun, 01 Jan 2006 00:00:00 GMT

Seawater Radiocarbon Evolution in the Gulf of Alaska: 2002 Observations Guilderson, Thomas P.; Roark, E. Brendan; Quay, Paul D.; Flood Page, Sarah; Moy, Christopher Oceanic uptake and transport of bomb radiocarbon as 14CO2 created by atmospheric nuclear weapons testing in the 1950s and 1960s has been a useful diagnostic for determining the carbon transfer between the ocean and atmosphere. In addition, the distribution of 14C in the ocean can be used as a tracer of oceanic circulation. Results obtained on samples collected in the Gulf of Alaska in the summer of 2002 provide a direct comparison with results in the 1970s during GEOSECS and in the early 1990s during WOCE. The open gyre values are 20-40 lower than those documented in 1991 and 1993 (WOCE), although the general trends as a function of latitude are reproduced. Surface values are still significantly higher than pre-bomb levels (~-105 or lower). In the central gyre, we observe ∆14C values that are lower in comparison to GEOSECS (stn 218) and WOCE P16/P17 to a density of ~26.8 sigma-t. This observation is consistent with the overall decrease in surface ∆14C values and reflects the erosion of the bomb-14C transient. We propose that erosion of the bomb-14C transient is accomplished by entrainment of low-14C water via vertical exchange within the Gulf of Alaska and replenishment of surface and subthermocline waters with waters derived from the far northwest Pacific.

Radiocarbon Determination of Particulate Organic Carbon in Non-Temperated, Alpine Glacier Ice

Sun, 01 Jan 2006 00:00:00 GMT

Radiocarbon Determination of Particulate Organic Carbon in Non-Temperated, Alpine Glacier Ice Steier, Peter; Shah, Sunita R.; Drosg, Roswitha; Pearson, Ann; Fedi, Mariaelenea; Kutschera, Walter; Schock, Martin; Wagenbach, Dietmar; Wild, Eva Maria Dating ice samples from glaciers via radiocarbon is a challenge that requires systematic investigations. This work describes an approach for extraction and accelerator mass spectrometry (AMS) 14C analysis of the particulate organic carbon (POC) fraction in glacier ice samples. Measurements were performed at VERA (Vienna Environmental Research Accelerator) on ice samples obtained mainly from the non-temperated ablation zone of the Grenzgletscher (Grenz Glacier) system (Monte Rosa Massif, Swiss Alps). The samples were obtained from 2 sampling sites situated roughly on a common flow line. The sample masses used were between 0.3 and 1.4 kg of ice, yielding between 18 and 307 micrograms of carbon as POC. The carbon contamination introduced during sample processing varied between 5.4 and 33 micrograms C and originated mainly from the quartz filters and the rinsing liquids used in processing. Minimum sample sizes for successful graphitization of CO2 in our laboratory could be reduced to <10 micrograms carbon, with a background in the graphitization process of ~0.5 micrograms of 40-pMC carbon. Evaluation of the whole procedure via 11 Grenzgletscher samples revealed a surprisingly large scatter of pMC values. We obtain a mean calibrated age of 2100 BC to AD 900 (95.4% confidence level), which is not significantly different for the 2 sampling sites. Discussions of these results suggest that single 14C dates of glacial POC are presently of limited significance. Future improvements with respect to analytical precision and sample characterization are proposed in order to fully explore the POC dating potential.