Showing papers by "Richard G. Fairbanks published in 2004"

IntCal04 terrestrial radiocarbon age calibration, 0-26 cal kyr BP

Abstract: A new calibration curve for the conversion of radiocarbon ages to calibrated (cal) ages has been constructed and internationally ratified to replace IntCal98, which extended from 0-24 cal kyr BP (Before Present, 0 cal BP = AD 1950). The new calibration data set for terrestrial samples extends from 0-26 cal kyr BP, but with much higher resolution beyond 11.4 cal kyr BP than IntCal98. Dendrochronologically-dated tree-ring samples cover the period from 0-12.4 cal kyr BP. Beyond the end of the tree rings, data from marine records (corals and foraminifera) are converted to the atmospheric equivalent with a site-specific marine reservoir correction to provide terrestrial calibration from 12.4-26.0 cal kyr BP. A substantial enhancement relative to IntCal98 is the introduction of a coherent statistical approach based on a random walk model, which takes into account the uncertainty in both the calendar age and the 14C age to calculate the underlying calibration curve (Buck and Blackwell, this issue). The tree-ring data sets, sources of uncertainty, and regional offsets are discussed here. The marine data sets and calibration curve for marine samples from the surface mixed layer (Marine04) are discussed in brief, but details are presented in Hughen et al. (this issue a). We do not make a recommendation for calibration beyond 26 cal kyr BP at this time; however, potential calibration data sets are compared in another paper (van der Plicht et al., this issue).

Marine04 marine radiocarbon age calibration, 0-26 cal kyr BP

Abstract: New radiocarbon calibration curves, IntCal04 and Marine04, have been constructed and internationally rati- fied to replace the terrestrial and marine components of IntCal98. The new calibration data sets extend an additional 2000 yr, from 0-26 cal kyr BP (Before Present, 0 cal BP = AD 1950), and provide much higher resolution, greater precision, and more detailed structure than IntCal98. For the Marine04 curve, dendrochronologically-dated tree-ring samples, converted with a box diffusion model to marine mixed-layer ages, cover the period from 0-10.5 cal kyr BP. Beyond 10.5 cal kyr BP, high-res- olution marine data become available from foraminifera in varved sediments and U/Th-dated corals. The marine records are corrected with site-specific 14C reservoir age information to provide a single global marine mixed-layer calibration from 10.5-26.0 cal kyr BP. A substantial enhancement relative to IntCal98 is the introduction of a random walk model, which takes into account the uncertainty in both the calendar age and the 14C age to calculate the underlying calibration curve (Buck and Blackwell, this issue). The marine data sets and calibration curve for marine samples from the surface mixed layer (Marine04) are discussed here. The tree-ring data sets, sources of uncertainty, and regional offsets are presented in detail in a companion paper by Reimer et al. (this issue). ABSTRACT. New radiocarbon calibration curves, IntCal04 and Marine04, have been constructed and internationally rati- fied to replace the terrestrial and marine components of IntCal98. The new calibration data sets extend an additional 2000 yr, from 0-26 cal kyr BP (Before Present, 0 cal BP = AD 1950), and provide much higher resolution, greater precision, and more detailed structure than IntCal98. For the Marine04 curve, dendrochronologically-dated tree-ring samples, converted with a box diffusion model to marine mixed-layer ages, cover the period from 0-10.5 cal kyr BP. Beyond 10.5 cal kyr BP, high-res- olution marine data become available from foraminifera in varved sediments and U/Th-dated corals. The marine records are corrected with site-specific 14C reservoir age information to provide a single global marine mixed-layer calibration from 10.5-26.0 cal kyr BP. A substantial enhancement relative to IntCal98 is the introduction of a random walk model, which takes into account the uncertainty in both the calendar age and the 14C age to calculate the underlying calibration curve (Buck and Blackwell, this issue). The marine data sets and calibration curve for marine samples from the surface mixed layer (Marine04) are discussed here. The tree-ring data sets, sources of uncertainty, and regional offsets are presented in detail in a companion paper by Reimer et al. (this issue).

Marine04 Marine radiocarbon age calibration, 26 ? 0 ka BP

Abstract: New radiocarbon calibration curves, IntCal04 and Marine04, have been constructed and internationally ratified to replace the terrestrial and marine components of IntCal98. The new calibration datasets extend an additional 2000 years, from 0-26 ka cal BP (Before Present, 0 cal BP = AD 1950), and provide much higher resolution, greater precision and more detailed structure than IntCal98. For the Marine04 curve, dendrochronologically dated tree-ring samples, converted with a box-diffusion model to marine mixed-layer ages, cover the period from 0-10.5 ka cal BP. Beyond 10.5 ka cal BP, high-resolution marine data become available from foraminifera in varved sediments and U/Th-dated corals. The marine records are corrected with site-specific {sup 14}C reservoir age information to provide a single global marine mixed-layer calibration from 10.5-26.0 ka cal BP. A substantial enhancement relative to IntCal98 is the introduction of a random walk model, which takes into account the uncertainty in both the calendar age and the radiocarbon age to calculate the underlying calibration curve. The marine datasets and calibration curve for marine samples from the surface mixed layer (Marine04) are discussed here. The tree-ring datasets, sources of uncertainty, and regional offsets are presented in detail in a companion paper by Reimer et al.

Effect of light and temperature on calcification and strontium uptake in the scleractinian coral Acropora verweyi

Abstract: Strontium thermometry has been suggested as a powerful tool for reconstructing sea- water surface temperature (SST). In corals, an inverse relationship between SST and skeletal Sr/Ca ratios has been found. However, this ratio might also vary with calcification, which in turn is depen- dent on light and temperature. The aim of this study was to improve our knowledge of the uptake of Sr 2+ as a function of light and temperature in the scleractinian coral Acropora verweyi. Two experi- ments were performed in which nubbins were acclimated over 4 wk either to 3 light intensities (100, 200 and 400 µmol m -2 s -1 ) or to 3 temperatures (20, 25, and 29°C) and growth rates were monitored. At the end of the 4 wk, nubbins were incubated, under the above light levels and temperatures, in individual beakers containing seawater spiked with the radiotracer 85 Sr. Parallel incubations were carried out in dark beakers, in order to compare rates of Sr 2+ incorporation in light and dark. The results obtained showed that growth rates were significantly higher under high light (0.16 ± 0.01 and 0.27 ± 0.01% d -1 for 100 and 400 µmol photons m -2 s -1 ) and under high temperature (0.06 ± 0.01% d -1 at 20°C to 0.35 ± 0.03% d -1 at 29°C). Rates of Sr 2+ incorporation into the coral skeleton were also higher under high light (32.4 ± 3.0, 72.9 ± 13.5 and 91.2 ± 9.0 nmol (g dry weight, DW) -1 d -1 , for corals cultured at 100, 200 and 400 µmol m -2 s -1 respectively) and high temperature (89 ± 14, 224 ± 38 and 436 ± 58 nmol (g DW) -1 d -1 for corals cultured at 20, 25 and 29°C respectively). Rates of Sr 2+ uptake were also 2 to 3 times lower in the dark than in the light, comparable with the incorporation of calcium. Our results finally show a strong correlation between Sr 2+ uptake and growth rates. Stron- tium uptake therefore follows the same pattern as calcium uptake, both ions being regulated by the calcification biochemistry.