The Integrated Ocean Drilling Program (IODP) Expedition 310 recovered drill cores from the drowned reefs around the island of Tahiti (17°40'S, 149°30'W), many of which contained samples of massive corals from the genus Porites. Herein we report on one well-preserved fossil coral sample: a 13.6 cm long Porites sp. dated by uranium series techniques at 9523 ± 33 years. Monthly delta18O and Sr/Ca determinations reveal nine clear and robust annual cycles. Coral delta18O and Sr/Ca determinations estimate a mean temperature of ca. 24.3°C (ca. 3.2°C colder than modern) for Tahiti at 9.5 ka; however, this estimate is viewed with caution since potential sources of cold bias in coral geochemistry remain to be resolved. The interannual variability in coral delta18O is similar between the 9.5 ka coral record and a modern record from nearby Moorea. The seasonal cycle in coral Sr/Ca is approximately the same or greater in the 9.5 ka coral record than in modern coral records from Tahiti. Paired analysis of coral delta18O and Sr/Ca indicates cold/wet (warm/dry) interannual anomalies, opposite from those observed in the modern instrumental record.

(a) delta234U = ([234U/238U]activity -1) * 1000. (b) [230Th/238U]activity = 1 - e(Lambda230T) + (delta234U(measured) / 1000) Lambda230 / (Lambda230 - Lambda234), where T is the age. Decay constants are 9.1577 * 10-6 yr-1 for 230Th, 2.8263 * 10-6 yr-1 for 234U [Cheng et al. (2000) doi:10.1016/S0009-2541(99)00157-6], and 1.55125 * 10-1010 yr-1 for 238U [Jaffey et al. (1971), doi:10.1103/PhysRevC.4.1889]. (c) The degree of detrital 230Th contamination is indicated by the [230Th/232Th] atomic ratio instead of the activity ratio.(d) Age corrections were calculated using an estimated atomic 230Th/232Th ratio of 4 ± 4 ppm. (e) delta234U(initial) corrected was calculated based on 230Th age (T), i.e., delta234U(initial = delta234U(measured) * e(Lambda234*T), and T is corrected age.

Supplement to: DeLong, Kristine; Quinn, Terrence Michael; Shen, Chuan Chou; Lin, Ke (2010): A snapshot of climate variability at Tahiti at 9.5 ka using a fossil coral from IODP Expedition 310. Geochemistry, Geophysics, Geosystems, 11, 1-14