The Maestrichtian Bolivina incrassata fauna (upper part of Upper Lambert Formation) of Hornby Island (northern Comox Basin) is now recognized in the southern Nanaimo Basin on Gabriola and Galiano Islands. The Maestrichtian planktonic index species Globotruncana contusa occurs in the Upper Northumberlahd Formation of Mayne Island and Globotruncana calcarata (uppermost Campanian) occurs| in the Upper Northumberland Formation of Mayne Island and also in the Upper Lambert Formation at Manning Point on the north shore of Hornby Island (Comox Basin).Very abundant benthonic and planktonic foraminiferal assemblages from the Upper Campanian Lower Northumberland Formation of Mayne Island enable paleoecological interpretations to be made using the Fisher diversity index, triangular plots of Texturlariina/Rotaliina/Miliolina, calcareous/agglutinated ratios, planktonic/benthonic ratios, generic models, and associated microfossils and megafossils. Combined with local geology and stratigraphy a relatively shallow neritic depositional environment is proposed for the Northumberland Formation in agreement with Scott but not Sliter who proposed an Outer shelf/slope environment with depths of 300 m or more.

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