Abstract

The Pine Point barrier reef complex began growth in early Givetian time, coincident with a gentle arch development in the underlying Keg River platform. As the barrier grew northward and up at an angle of 1 - 2 degrees over its own fore-reef, subsequent tectonic adjustments (hinges) were superimposed upon the barrier development. The first adjustment, the “South Hinge”, caused a higher rate of subsidence in the back-reef area with the formation of extensive pans in which the Muskeg evaporites precipitated. At this stage early dolomitization of the barrier complex occurred, possibly due to reflux of magnesium-rich brines from the pan areas. This stage came to a halt, but renewed tectonic movements initiated the “Main” and “North Hinge” structures. Later, after burial of the barrier, these two hinges became important channelways for mineralizing solutions. They also controlled the distribution of the coarse crystalline “Presqu’ile dolomite”. Barrier development came to an end between middle to late Givetian (Watt Mountain) time. A marine regression exposed the upper part of the barrier to karsting which provided additional ground preparation for later mineralization. Renewed sedimentation at late Givetian time buried the barrier under platform carbonates of the Slave Point Group, followed by Upper Devonian Hay River shales.