Towards accurate numerical calibration of the Late Triassic: High- precision U-Pb geochronology constraints on the duration of the Rhaetian

摘要: Numerical calibration of the Late Triassic stages is arguably most controversial issue in Mesozoic stratigraphy, despite its importance for assessing mechanisms environmental perturbations and associated biologic consequences preceding end-Triassic mass extinction. Here we report new chemical abrasion–isotope dilution– thermal ionization spectrometry zircon U-Pb dates volcanic ash beds within Aramachay Formation Pucara Group northern Peru that place precise constraints on age Norian- Rhaetian boundary (NRB) duration Rhaetian. The sampled bed–bearing interval located just above last occurrence bivalve Monotis subcircularis, placing this stratigraphic sequence uppermost Norian, perhaps ranging into earliest Zircon constrain deposition to be between 205.70 ± 0.15 Ma 205.30 0.14 Ma, providing NRB. Combined with previously published bracketing Triassic-Jurassic boundary, estimate a 4.14 0.39 m.y. This ends prolonged controversy about stage has fundamental implications rates paleoenvironmental deterioration culminated