Cambrian linguliformean brachiopods of the Pika and Sullivan Formations (Miaolingian), southern Rocky Mountains, Alberta, Canada

A low-diversity Miaolingian linguliformean brachiopod fauna is described from the middle Cambrian Pika and Sullivan formations in the southern Canadian Rocky Mountains. The sampled Pika Formation consists of lime mudstone, whereas the Sullivan Formation consists of coarse-grained, commonly oolitic grainstone interbedded with lime mudstone and siltstone of inner detrital belt lithological aspect in a storm-influenced, but distal shelf setting. Brachiopods are most common in the grainstone interbeds where they occur with disarticulated trilobite sclerites and eocrinoid ossicles. Most valves are broken to some degree due to transport and/or reworking. These coarse-grained beds were deposited in the deeper shelf environment by large-scale events such as a storms, and tsunami off-surge is considered a possibility given the regional tectonic setting. The fauna consists of obolids with only rare specimens of an indeterminate species belonging to the paterinid Micromitra Meek found in the Bolaspidella trilobite Biozone (Drumian Stage) of the Pika Formation. The assemblage from the Cedaria trilobite Biozone (Guzhangian Stage) of the Sullivan Formation includes the obolids Dicellomus politus Hall, D. cf. D. amblia Bell, D. appalachia Walcott, and D. nanus Meek and Hayden. No acrotretids were recovered. This low-diversity fauna probably reflects the deeper and more outboard depositional setting of the Sullivan Formation in comparison to other contemporaneous units elsewhere. Valves recovered from a more distal setting in the Sullivan Formation at Mount Murchison show a wider range of sizes by comparison to those from Windy Point, except for the ones belonging to D. politus perhaps indicating lower intensity of high-energy events.