An open-system model for U-series age determinations of fossil corals

Coastal tectonics on the eastern margin of the Pacific Rim: late Quaternary sea-level history and uplift rates, Channel Islands National Park, California, USA

“…These corals have U concentrations within the range typically found in fossil corals from California and have low concentrations of Th, but have 230 Th/ 232 Th values that are not quite as high as the San Miguel Island samples reported here. Although the new halflives do not change the ages significantly from those given in Pinter et al (1998a), it is worth pointing out that the lower 230 Th/ 232 Th values (indicating some inherited 230 Th from detrital minerals) and the higher-than-modern, back-calculated initial 234 U/ 238 U values probably bias the samples to somewhat older apparent ages (Gallup et al, 1994;Thompson et al, 2003). If this interpretation is correct, then the true ages of the Santa Cruz Island corals are likely similar to those of San Miguel Island (i.e.,~120 ka).…”

Sea level changes during the last and present interglacials in Sal Island (Cape Verde archipelago)

“…Several processes may account for such a trend (e.g., Thompson et al, 2004), but their impact on the calculated ages seems of minor importance in our case. This is illustrated by seriate measurements (Table 1) in one S. radians sample showing three growth phases, the last two of which are separated by a stage of intense bio-erosion.…”

Late Quaternary sea-level history and the antiquity of mammoths (Mammuthus exilisandMammuthus columbi), Channel Islands National Park, California, USA

“…All corals have U contents similar to those of modern and fossil B. elegans described elsewhere from California and Baja California, Mexico (Muhs et al, 2002a(Muhs et al, , 2006(Muhs et al, , 2012(Muhs et al, , 2014a, indicating no significant diagenetic gain or loss of U ( Delanghe et al, 2002). Sample SRI-27-B has an initial 234 U/ 238 U value of~1.158, indicating the possibility of a bias (perhaps as much as~2-3 ka) to a slightly older apparent age, based on the models of Gallup et al (1994) and Thompson et al (2003). Reduction of the apparent age of SRI-27-B by~2-3 ka would result in an age that is still within the range of ages of the other corals, which is 82.9 ± 0.5 ka to 78.6 ± 0.5 ka.…”