On the age of the Queen Charlotte Group of British Columbia
The Cretaceous Queen Charlotte Group has traditionally been divided into three lithostratigraphic units in the type region: the Haida, Honna, and Skidegate formations. The sandstone member of the Haida Formation is commonly rich in fossil molluscs, and its Albian age is well documented. Megafossils are less abundant in the shale member of the Haida Formation and in the Honna and Skidegate formations; consequently, the ages of these units have not been well defined. In the last century, however, the early Turonian bivalve Mytiloides labiatus (s.l.) was identified from both the shale member of the Haida and the Skidegate Formation; unfortunately, the stratigraphic significance of these occurrences was not fully appreciated at that time. More recent collections of fossil molluscs from the Queen Charlotte Group have verified that both the Skidegate Formation and the upper part of the Haida shale member include strata of Turonian age, thus indicating the two units are, at least in part, lateral equivalents. Based on the presence of the megafossils Peroniceras (s.s.) sp. and Plesiotexanites sp., it is concluded that the greater part of the Honna Formation is of Coniacian age and caps the stratigraphic sequence.