Lower and Early Middle Cambrian Formations near Mount Robson, British Columbia and Alberta

Five formations and part of a sixth were examined in order to resolve conflicting reports as to their age and lateral relationship. The formations are redescribed at their type sections and equivalent strata are described at a control section. It is concluded that the Lower Cambrian Mural, Mahto, and Hota Formations and the Middle Cambrian Chetang Formation are valid and that the Tah (= Mural) and Adolphus (= Hota) Formations should be suppressed. The boundary between the Nevadella and Bonnia-Olenellus Zone falls within the middle unit of the Mural. The Lower – Middle Cambrian boundary is located at or very near the contact between the Hota and overlying Chetang Formation. This is a sharp lithologic contract, but no physical evidence of an unconformity was noted.