DOI: 10.25921/r5ts-qc15
title: NOAA/WDS Paleoclimatology - Barbados - Last Glacial Maximum Sea Level Record

description: 230Th/234U and 14C dating of Barbados corals has extended the calibration of 14C years B.P. to calendar years B.P. beyond the 9200 year tree ring series (Bard et al., 1990). This now permits the conversion of 14C chronozones, which delimit major climate shifts in western Europe, to calendar years. The Younger Dryas chronozone, defined as 11,000 to 10,000 14C years B.P., corresponds to 13,000 to 11,700 calendar years B.P. This calibration affects the interpretation of an intensely studied example of the "Younger Dryas climate event," the δ18O anomaly between 1785 and 1793 m in Dye 3 ice core. The end of the δ18O anomaly in Dye 3 ice core has been dated by measurements of 14C in air bubbles (Andree et al., 1984, 1986) and by annual layer counting (Hammer et al., 1986). The older 14C dates fall out of the range of the tree ring calibration series but can now be calibrated to calendar years using the Barbados 230Th/234U calibration. The 14Ccorrected age for the end of the δ18O event is 10,300 ± 400 calendar years B.P. compared to the annual layer counting age of 10,720 ± 150 years B.P. Thus, the "Younger Dryas" event in the Dye 3 ice core ends in the Preboreal chronozone (11,700 to 10,000 calendar years B.P.) and is not correlative with the end of the Younger Dryas event identified in pollen records marking European vegetation changes. The end of the Dye 3 δ18O event is, however, correlative with the end of meltwater pulse IB (Fairbanks, 1989), marking a period of intense deglaciation with meltwater discharge rates exceeding 13,000 km³/yr.
description: From Table 1 caption (Fairbanks, 1990): Barbados data are from Fairbanks (1989) and Bard et al. (1990) or are presented here for the first time. All 14C measurements were made in the Lamont radiocarbon laboratory by Guy Mathieu unless otherwise indicated. Data for Porities asteroides (Pa) samples from Barbados are listed, but they are not used in the sea level reconstruction. The Porities asteroides (Pa) data provide lower limits for sea level during the last glacial maximum. Sample 12-30-2 is located below a subaerial exposure surface capping an older reef. Data for other Caribbean islands are from the compilation of Lighty et al. (1982). 14Cc kyr is the reservoir corrected age computed by subtracting 0.4 kyr from the 14C age. Depth (m)c indicates uplift corrected depth using a mean uplift rate of 34 cm/kyr (Fairbanks, 1989) and the 14Cc age. In the future, the corrected depth will be based upon Th/U age estimates once the Th/U age dates are completed on the remaining samples. Replicate 14C measurements were averaged for the purpose of plotting the sea level curve and for estimating the uplift correction of individual samples. The exceptions are samples 7-12-2, 7-13-1, 9-27-5 which had initial age dates out of stratigraphic sequence. These samples were re-dated and the new age dates are stratigraphically consistent.Note:E. Bard presented two regression equations to describe the relationship between 14-C and Th/U ages at the 4th International Congress on Paleoceanography (Kiel, 1992): linear relationship: "true age"=1.24(14-C age) - 840; polynomial relationship: "true age"=-5.85x10^-6(14-C age)^2 + 1.39(14-C age) - 1807