Stratigraphic correlation and paleogeography of the Upper Cretaceous Suquash Outcrop Area, Vancouver Island, Canada

The geology of the Suquash Outcrop Area (OA) remains enigmatic despite over 150 years of economic interest in exploiting coal seams contained therein. Here, we use uranium–lead dating of detrital zircon grains combined with macrofossil- and palynology-based biostratigraphy to determine the ages of stratigraphic units. Age assignments are combined with legacy core descriptions and new data from measured outcrop sections to reconstruct the geology of the Suquash OA. Our results show that strata in the Suquash OA were deposited during two distinct phases: (1) Campanian and (2) late Maastrichtian to early Danian. Coal beds occur mainly in the late Maastrichtian–early Danian phase. The Suquash OA is also intersected by a series of faults and shows some evidence of deformation between deposition of Campanian strata and late Maastrichtian–early Danian strata. During both phases, the Suquash OA formed the northwest extent of the Georgia Basin: the Campanian phase correlates to the Protection Formation and the younger phase correlates to the Oyster Bay Formation. The strata deposited in the Suquash OA contain Early Cretaceous dinocysts that are probably derived from the Queen Charlotte Group in the Queen Charlotte Basin and/or the Gambier Group in the Coast Plutonic Complex. This study confirms the association of strata in the Suquash OA with time equivalent strata in the Georgia Basin and confirms the presence of a major disconformity between the lower and upper Nanaimo Group in the region.