In situ LA-ICP-MS U–Pb geochronology has been performed on apatite and zircon within thermally recrystallized clast-laden and clast-poor impact melt rocks from the Brent impact structure. The reported zircon U-Pb dates are 238 U-206 Pb weighted mean dates with ±2σ analytical uncertainties corrected for initial 230 Th disequilibrium (figs. (b) Modified U‐Pb age data for the zircon samples. Stratigraphically constrained basalt flows, such as the North Mountain and Preakness basalts, provide the most straightforward means of directly dating the Triassic and Early Jurassic stratigraphy ( Fig. Lower intercept age for FCT zircon … The oldest-known air-breathing land animal is the millipede Pneumodesmus newmani, found in the Cowie Harbour Fish Bed at Stonehaven, Scotland.Here we report the youngest, most concordant 238 U-206 Pb zircon age from ash below the fish bed of 413.7±4.4 Ma (±2σ), whereas the youngest age from a tuffaceous sandstone above the fish bed is statistically indistinguishable at …
A zircon U-Pb study of the evolution of lunar KREEP By A.A. Nemchin, R.T. Pidgeon, M.J. Whitehouse, J.P. Vaughan and C. Meyer Abstract SIMS U-Pb analyses show that zircons from breccias from Apollo 14 and Apollo 17 have essentially identical age distributions in the range 4350 to 4200 Ma but, whereas Apollo 14 zircons additionally show ages from 4200 to 3900 Ma, the Apollo 17 samples … In this calculation, a modified normalization value (206 Pb/ 238 U = 0.2302) was used. GSA Data Repository Item 2015337.
Bull. Volcanic rocks in the ore field have even been proposed to include both ages. The Pb/U ratios in zircon samples were calibrated by normalizing to SRM610 being 206 Pb/ 238 U = 0.2249. Malkowski, M.A., Graham, S.A., and Grove, M., Unzipping the Patagonian Andes Long-Lived Influence of Rifting History on Foreland Basin Evolution: Lithosphere, doi:10.1130/L489.1. Previous zircon U–Pb geochronological studies on ignimbrites and tuffs from this area have yielded conflicting ages of 157–161 Ma (Early Upper Jurassic) and 137–144 Ma (Early Lower Cretaceous). 1.- Âge des métagranites de Canaveilles dans les Pyrénées et la Montagne Noire (France) : U-Pb sur zircon (dilution isotopique et SHRIMP) d'après un article d'Alain Cocherie et al.
2 ). Appendix 1: Locations of U-Pb zircon samples (WGS84). Supplementary Data: U-Pb zircon geochronology by LA-ICPMS . Most detrital zircon studies will use the 'usual' ages, particularly utilising 206 Pb/ 238 U for ages younger than a certain cutoff (e.g.
S3 and S4) .