Background

Description

Nituk Formation 1 (pPni1): Siltstone, Sandstone and Conglomerate

Nituk Formation 2 (pPni2): Phyllite

Phyllite outcrops are generally small, rarely more than 10 m thick. Millimetre to centimetre-thick laminations are almost always present. Phyllites have undergone complete recrystallization and contain microblastic quartz and muscovite as the major minerals (Moorhead, 1989).

Nituk Formation 3 (pPni3): Limestone, Dolomitic Limestone

This subdivision occurs as generally massive outcrops. When visible, beds vary in thickness from 1 to 20 cm. It consists mainly of micro-grained dolomite with very few internal structures. Quartz vein networks are 1 to 5 cm wide and randomly cut the rock. There is a local detrital component representing up to 20% of the rock, which consists of quartz and rarely of plagioclase grains (Moorhead, 1989).

Nituk Formation 4 (pPni4): Basalt

The thicknesses of basaltic flows range from 2 to 8 m. These flows are typically massive and rarely cushioned. They are generally deformed and are affected by a strong schistosity. Several outcrops are cut by millimetre-thick quartz veins. These basalts are similar to those of the Beauparlant Formation (Moorhead, 1989).

Nituk Formation 5 (pPni5): Iron Formation

Few information is available.

Nituk Formation 6 (pPni6): Micaceous Sandstone

This subdivision consists of homogeneous and micaceous quartzitic sandstone which ranges from 70 to 1700 m in thickness. Outcrops are located in the western area of Joy Bay, north of Grunérite Lake and south of Vicenza Lake (St-Onge and Lucas, 1993). Sandstone is composed of quartz and of more than 20% metamorphic biotite and muscovite. This sandstone has beds about ten centimetres thick and is characterized by good sorting and rounded millimetric grains, as well as abundant centimetric quartz veins (St-Onge and Lucas, 1993).

Thickness and Distribution

Refer to the Description section.

Dating

A sill of the Lac Bélanger Suite intruding into the basal portion of the Nituk Formation was dated 2038 +4/-2 Ma (Machado et al., 1993), thus defining a minimum age for the Nituk Formation.

Stratigraphic Relationship(s)

The Nituk Formation is usually in decollement fault contact with the Archean basement to the north and south of the orogen. Occasionally, particularly in the Grunérite Lake (sheet 35H08) and Korak River (sheet 35C14) areas, the Nituk Formation lies in stratigraphic contact on to of the Kuuvvaluk Formation. The unit is usually overlain by the Beauparlant Formation, either in stratigraphic or structural contact (thrust fault). In the Dumas Lake area (sheet 35G07), where the thickness of the Nituk Formation is considerably decreasing westward, the unit has a higher proportion of volcanic layers and laterally changes to the Beauparlant Formation. Further west, the Nituk Formation represents only a small proportion of the Southern Domain rocks.

Paleontology

No fossil has been reported.

References