Early Cretaceous (?early late Albian) echinoderms from northeastern British Columbia, Canada

摘要

An echinoderm association is reported from the ? early late Albian Paddy Member of the Peace River Formation of British Columbia, Canada. The association includes Frasericrinus mauricensis gen. et sp. nov., two additional distinctive crinoid column types, a poorly preserved asteroid, and an umbilical fragment of the cephalopod Stelckiceras. This is the first report of a Cretaceous isocrinid from North America. The echinoderm fossils are from the top of a succession of storm-deposited sandstones and mudstones (Boulder Creek Formation) that can be correlated southward into nearshore and terrestrial facies of the Paddy Member of the Peace River Formation. The echinoderm fossils were buried (and probably lived) about 12-14 km from the contemporaneous shoreline in an estimated water depth of 10-20 m. Integration of biostratigraphic and allostratigraphic schemes suggests that the echinoderms are of earliest late Albian age. The association of the echinoderm fauna with ammonites of Boreal affinity indicates deposition in northern waters, although the presence of Tethyan inoceramids in apparently coeval Paddy Member strata 270 km to the east suggests that northward-advancing water from the Gulf of Mexico had reached northwestern Alberta, if not actually merged with the Boreal embayment. The nearshore occurrence of Cretaceous stalked crinoids is indicative of an asynchronous, gradual migration of stalked crinoids to deep-water habitats, to which they are restricted in modern oceans.