New biostratigraphic data from the Lower Jurassic Fernie Formation in the subsurface of west-central Alberta and their stratigraphic implications

Abstract

Geophysical gamma-ray log responses and examination of cores from select wells of the lower Fernie Formation document important correlations of several new lithologic units recognized in the subsurface of west-central Alberta. Ammonite faunas and coccolith floras recovered from these cores are illustrated and provide new ages for several of these units, requiring a revision of their correlation with surface stratigraphy of the west-central Alberta foothills. The organic-rich, fine-grained west-central Alberta subsurface lower Fernie Formation sediments are Hettangian to late Toarcian in age and are, therefore, correlative with outcrops of unnamed basal Fernie strata of northeastern British Columbia, Nordegg Member cherty limestones of the Cadomin and Nordegg areas, and with the Red Deer Member and Poker Chip Shale at outcrop in west-central Alberta.