The white coarsely crystalline space-filling and replacement, late-diagenetic Mississippi Valley-type dolomite of the Manetoe facies occurs across a broad area of at least 15,000 sq km in the southern Mackenzie Mountains of the Northwest Territories. Through most of this area it is stratiform and confined to a thin (< 100 m thick) stratigraphic interval under a shale unit within a lower Paleozoic carbonate sequence. Some large vertical developments of the Manetoe facies, such as at the Kotaneelee and Pointed Mountain gas fields, occur in the eastern part of this region where the overlying shale of the Headless Formation is thin. These large dolomite masses have a core of dolomite-cemented breccia and are surrounded by a halo of replacement dolomite. Solution-collapse b eccias and large solution cavities are common throughout. Quartz and bitumen are the final vug infillings. The pronounced curvature of Manetoe dolomite crystal faces is similar to that displayed by many Mississippi Valley-type dolomites.

These dolomites are nearly stoichiometric with a mean of 51 mole % CaCO₃, and they exhibit a high degree of cation order. The range of carbon isotope values (+ 1.33 to -2.99 ^dgr C¹³PDB) and a sodium concentration of ~100 to 350 ppm are typical for this type of dolomite. But the range of oxygen isotope values (-8.03 to -17.33 ^dgrO¹⁸PDB), the extremely high strontium content of ~200 to 1,000 ppm, and an iron content less than 120 ppm is atypical and must reflect precipitation from a medium of unusual composition, enriched in strontium but depleted in iron and in the O¹⁸ isotope.

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