The earliest descriptions of this unit come from the regional mapping work by Roscoe (1957) and Fahrig (1965). Dressler (1974) subsequently provided a more detailed description of the lithologies comprising the unit north of Nachicapau Lake (sheet 24C09). Subsequently, Dressler (1979) proposed the name Nachicapau Formation for a package of sedimentary rocks grouping argillite, turbidite and dolomite beds located north of Nachicapau Lake, from which the unit takes its name. Dressler (1979) gave a more complete description of the formation and mentioned the possibility that dolomites correspond to those of the Abner Formation (Bérard, 1965; abandoned, equivalent to the Denault Formation). He also indicated that insertion of the Nachicapau Formation clay-turbidite-dolomite package into the stratigraphy of the central Labrador Trough is speculative. According to Dressler (1979), field relationships suggest that the Nachicapau Formation is overlying the Mistamisk Formation (Dimroth, 1972, 1978; abandoned, equivalent to the Bacchus Formation) and underlying the Murdoch Formation. The Nachicapau Formation was later recognized as partly equivalent to the Bacchus and Denault formations (Clark and Wares, 2004). The name Nachicapau Formation was therefore abandoned.

The Nachicapau Formation is equivalent to the Bacchus Formation (Swampy Bay Group) and the Denault Formation (Attikamagen Group). Consequently, the name Nachicapau Formation was abandoned and the outcrop areas corresponding to this unit were assigned to the appropriate units (Clark and Wares, 2004).

Note that west of Le Moyne Lake (sheet 24C16), Dressler (1979) mapped some of the rocks associated with carbonatite of the Le Moyne Carbonatite Complex (Birkett and Clark, 1991) and the Douay Formation (Clark and Wares, 2004) as dolomite of the Nachicapau Formation.

References