The Cretaceous Cadomin Formation is the basal unit of the Blairmore Group i
n the southern Rocky Mountains and Foothills of Alberta and British Columbi
a. The Cadomin is predominantly a conglomerate and is overlain by sandstone
of the Dalhousie Formation. The Pocaterra Creek Member is a conglomerate,
mudstone, and caliche-bearing subunit of the Cadomin Formation, having a re
stricted westerly distribution. The ages of the Cadomin and Dalhousie forma
tions have not been well constrained previously because the units are gener
ally too coarse-grained for optimum palynomorph recovery. The strata have p
reviously been considered to be of Barremian-Aptian age, except for the Poc
aterra Creek Member which is of Berriasian age. For this study, twenty-two
palynology samples from the Crowsnest Pass area were examined, spanning str
ata from the Mist Mountain Formation to the Dalhousie Formation. Age interp
retations are possible for nine samples.
Palynological assemblages from a conglomeratic outcrop at Bellevue are of L
ate Jurassic-earliest Cretaceous age. These assemblages argue for inclusion
of a conglomeratic bed in the Mist Mountain Formation east of the Fernie a
rea.
Palynological assemblages from the Cadomin and Dalhousie formations fall in
to three main groups. One assemblage group has neither angiosperm nor Appen
dicisporites pollen, and may be of Berriasian-Valanginian age. Another grou
p lacks angiosperm pollen but is characterized by the presence of Appendici
sporites and Klukisporites, and is probably of Hauterivian to early Barremi
an age. A third group has the angiosperm pollen Clavatipollenites and Retim
onocolpites, but no Appendicisporites and rare Klukisporites, and is probab
ly of late Barremian to ?early Aptian age. These ages suggest that depositi
on of the Cadomin Formation in the study area occurred over a long period o
f time during the Neocomian, beginning with the Berriasian Pocaterra Creek
Member. This thin stratigraphic unit accumulated over a long time period as
northerly-flowing rivers migrated laterally across the 50 km E-W extent of
the braid plain, thereby producing many local diastems of varying duration
.