New U–Pb zircon ages integrated with ammonite biochronology from the Jurassic of the Canadian Cordillera

J Pálfy, J K Mortensen, P L Smith, R M Friedman, V McNicoll, M Villeneuve
2000 Canadian journal of earth sciences (Print)  
The accuracy of published Jurassic time scales is compromised by a paucity of sufficiently accurate and stratigraphically well-constrained isotopic dates. U-Pb dating of volcaniclastic rocks within fossiliferous marine successions is a method suitable of providing additional useful calibration points. Stikinia and Wrangellia, two of the major accreted terranes of the Canadian Cordillera, comprise volcanosedimentary assemblages of magmatic arc origin. Within them we selected sections from which
more » ... ections from which we report 14 new U-Pb zircon ages that are integrated with ammonite biochronology at the zonal level. Poor zircon recovery and complex U-Pb systematics made it difficult to obtain precise ages for many of the samples. The following ages were determined (with 2σ errors): 1940 1 8 91 . . 9 , , , − + du Bathonien supérieur au Callovien inférieur. Cinq autres dates sont moins précises mais elles fournissent quand même quelques cadres pour la calibration de l'échelle de temps. On se servira des dates U-Pb citées ici et d'une foule d'autres dates isotopiques de la cordillère obtenues récemment pour effectuer une grande révision de l'échelle de temps du Jurassique. [Traduit par la Rédaction] Pálfy et al. 567
doi:10.1139/e99-115 fatcat:ieouu6odq5eyvbx5zgjwqyvkxm