The eastern extent of the Risky Formation (Ediacaran), Mackenzie Mountains, Northwest Territories

Abstract

Newly documented exposures of dolostone, sandy dolostone, and quartz arenite in the Natla structural panel, western Wrigley Lake map area (NTS 95-M; Mackenzie Mountains, Northwest Territories) are assigned to the Ediacaran Risky Formation. Similarities in lithology and stratigraphic succession with the type area of the formation (Sekwi Brook structural panel, Mackenzie Mountains) support the assignment. The newly recognized occurrence of Risky Formation is within an interval previously mapped as Backbone Ranges Formation and implies that the base of the Cambrian is much higher within that unit than is suggested by previous correlations. The Risky Formation forms an eastward-thinning tongue within the Backbone Ranges Formation and may extend as far east as the hanging wall of the Plateau Fault. Karst breccia within the Risky Formation hosts base-metal mineralization in the type area of the unit and in the Wernecke Mountains. Thus, there may be limited exploration potential in the eastward extension of the Risky Formation.