Geochronology in Support of the Alberta Table of Formations: Uranium-Lead Isotope Dating of Zircon from Upper Albian Ash Beds in Alberta

The purpose of this study is to confirm and possibly refine the age and stratigraphic correlations of Upper Albian strata in Alberta using U-Pb isotope dating of zircons collected from ash beds in subsurface drill core. This study strives to update the late Albian age boundaries for the Alberta Table of Formations, created and maintained by the Alberta Geological Survey. The ages of Upper Albian strata in the Alberta Basin have been determined primarily through a biostratigraphic approach, which leaves a considerable degree of uncertainty with regards to the true depositional age of these sand-rich intervals. Ash beds are useful in dating deposits due to their high potential to preserve depositional-aged grains of zircon. Ash beds from subsurface core that intersect Upper Albian strata were collected from the Paddy Member of the Peace River Formation (northwestern Alberta), the Viking Formation (central Alberta), and the Bow Island Formation (southern Alberta). Fourteen ash beds from 13 wells across the province were sampled for zircon grains to be dated by U-Pb analysis using laser-ablation inductively coupled plasma–mass spectrometry. Nine of the samples had enough zircon grains to produce usable dates for the formations. The reported average ages for the Paddy Member (Peace River Formation) include: 100.7 ± 1.4 Ma and 101.3 ± 1.4 Ma. The reported average ages for the Viking Formation include: 98.8 ± 1.6 Ma, 98.6 ± 2.5 Ma, 98.5 ± 2.8 Ma, and 98.2 ± 1.7 Ma. The reported average ages for the Bow Island Formation include: 104.0 ± 1.9 Ma and 99.3 ± 1.4 Ma. It was determined that future studies must be conducted to reliably adjust or reconfirm the age boundaries of the Viking, Peace River, and Bow Island formations on the Alberta Table of Formations.