In the South Nahanni River area of the District of Mackenzie, the Middle Ordovician Sunblood Formation comprises mainly limestones and dolostones of intertidal and shallow-subtidal origin, as indicated by the presence of desiccation polygons, fenestral fabric, and oncolites. Faunas of well-preserved, silicified trilobites from a low-diversity, nearshore,Bathyurus-dominated biofacies are compositionally distinct from faunas in correlative strata around North America that represent different shelf to upperslope biofacies. A temporal biostratigraphy applicable to nearshore biofacies through much of the Whiterockian Series consists of five zones, in ascending order:Bathyurus mackenziensis, B. sunbloodensis, B. margareti, B. nevadensis, andB. granulosus.Twenty-six species are assigned to 18 genera, of whichLudvigsenellais new. Three new species ofBathyurusareB. mackenziensis, B. sunbloodensis, andB. margareti.
No takes yet. Share an insight, caveat, or question.
Tremblay et al. (1991) studied this question.