The Upper Proterozoic 'Limestone Unit' of the Horsethief Creek Group in the northern Dogtooth Mountains consists of deformed sedimentary and metasedimentary rocks with complex depositional and erosional relationships. They are interpreted to represent a westwardly prograding terrigenous and carbonate wedge in a continental margin situation. Shoaling resulted in differential carbonate deposition on top of a largely pelitic succession. Sea level fluctuations produced a complex unit characterized by alternating erosion and sedimentation, in different fades from east to west. This was succeeded by terrigenous clastic sediments with easterly or southeasterly provenance. The last recognizable events produced a widespread carbonate and sandstone blanket.A carbonate unit of similar stratigraphic position occurs in several locations north–northwest of the Dogtooth Mountains, approximately along a line paralleling the trend of Phanerozoic fades belts.