The first descriptions of these lithologies come from the work of Roscoe (1957). The name Savigny Formation was introduced by Dimroth (1968) in the Savigny Lake area to designate a sequence of finely bedded grey silty slate. Rocks of the Savigny Formation were mapped by Fahrig (1969), Dimroth (1969, 1970a, 1972, 1978), Dressler (1973, 1974, 1975, 1979) and Clark (1984).

Unit pPsv1 consists of mudstone, slate and siltstone typically dark grey in fresh surface, light grey or rusty-brown in altered surface, finely bedded and laminated (Dimroth, 1969, 1978; Dressler, 1979). These rocks form centimetric to metric layers, locally interbedded with centimetric beds of wacke and grey dolomite having a light brown patina (Dimroth, 1978; Dressler, 1979). In the Doutreleau Lake area (sheet 24C10), Dressler (1979) mentions, among other things, the presence of about twenty mudstone beds (2 cm to 6 m thick, averaging 5-20 cm) interbedded with dark grey dolomite beds 2 cm to 1.2 m thick. Black graphitic dolomite beds ~2 cm thick are interbedded in mudstone and slate at the base of the Savigny Formation in the High Falls area (sheet 24C01) (Dimroth, 1978). Ankerite porphyroblasts are commonly observed (Dimroth, 1978; Chevé, 1993). Mudstone and slate generally display very regular stratification with thin, millimetre-thick parallel laminae (1-10 mm) and fine crossbedding (Dimroth, 1969, 1978; Dressler, 1979). Sorting is observed locally, while flaser-like lamination is rare (Dimroth, 1969). Siltstone occurs in thin,1 to 10 mm-thick laminae and has one cleavage, locally two (Dressler, 1979). Dolomite is usually finely bedded and recrystallized. It is arenaceous or argillaceous in places. Very thin veinlets of chalcedonic chert, a few millimetres apart, are commonly observed in dolomite. They are perpendicular to the dolomite’s stratification (Dressler, 1979).

In the Mort Lake area, west of Cambrien Lake (sheets 24C03 and 24C06), the unit consists of dark grey, fissile and laminated mudstone and siltstone, locally interbedded with thin (1 cm) black sandstone. In addition to lamination, sedimentary structures are sparse and include ripples, sorting, siltstone-mudstone clasts in sandstone beds and load prints. Disseminated pyrite is observed locally. The base of the unit is clearly visible on the shore of Cambrien Lake, overlying grey dolomite of the Pistolet Group. There, it is represented by a 1 m-thick layer of folded and crenulated, black pyritic, highly graphitic slate. Slate is overlain by very slightly deformed, locally graphitic mudstones (Clark, 1984). Clark (1984) speculated that these black slates may correlate with black slates of the Hautes-Chutes Formation.

Savigny Formation 2 (pPsv2): Black Graphitic Slate, Locally Pyritic; Interbedded Black Graphitic Wacke

Thickness and distribution

The Savigny Formation belongs to the Cambrien and Schefferville lithotectonic zones, as defined by Clark and Wares (2004). It outcrops well in the Savigny Lake basin (sheet 24C07) and at the High Falls of the Swampy Bay River (sheet 24C01), as well as along the Swampy Bay River (Dimroth, 1969). It is >600 m thick in the Savigny Lake area and <300 m west of Otelnuk Lake (sheet 24C01) (Dimroth, 1969, 1978). The formation gradually thins from Savigny Lake to Otelnuk Lake (Dimroth, 1978). It is also found west of Cambrien Lake in the axial part of the Rivière de la Mort Syncline (sheet 24C03), where it is estimated to be 35 m thick (Clark, 1984). East of Cambrien Lake (sheet 24C06), the formation is >45 m thick, but its total thickness may be greater than reported (Clark, 1984). The Savigny Formation was mapped by Dressler (1979) SW of Canichico Lake (sheets 24C10 and 24C15) and in the Edgar Lake area (sheet 24C10). Dressler (1979) also mapped it west of Doutreleau Lake (sheets 24C07 and 24C10), where it represents the extension of the terrain mapped by Dimroth (1978).

Dating

None.