Type Locality:

26 km south of Glenelg Bay, northern Victoria Island.

Distribution:

730 m with top of formation lost to erosion. Distributed in two patches in the centre of the Minto Arch, covering about 750 sq. km. The Natkusiak Formation is at the core of the gently folded Holman Island Syncline.

Lithology:

A sequence of dark grey to greenish-grey basaltic volcanic flows ranging from 15-60 m thick, commonly thinly amygdaloidal at the bottom and extensively so at the top of the flow, with dense basalt in the core. Poorly indurated, calcite-veined red and green agglomerate 0-90 m thick is locally present at the base of the formation. The agglomerate is composed of volcanic rock fragments, bombs and various baked sedimentary rocks in a calcite and tuff matrix. The formation is extensively intruded by diabasic gabbro sills and dykes, particularly toward the axis of the Hol-man Island syncline. The basaltic flows and dolerite intrusives may be components of the same (Franklinian) magmatic episode (Baragar, 1976) and share the same age - 635 to 640 m.y. - as determined by Christie (1964b) on samples of the intrusive from the head of Glenelg Bay.

Relationship:

Disconformable with the underlying Shaler Group (Baragar, 1976).

Other Citations:

Thorsteinsson and Tozer, 1961, 1962; Christie, 1964b; Baragar, 1976.