The Toobally fault is a north-trending structure occurring along the west shore of northern Toobally Lake (95D/8) that juxtaposes Neoproterozoic-Cambrian sedimentary and volcanic rocks (to the west) against Devonian-Carboniferous sedimentary rocks (to the east). Paleozoic units east of the fault are tentatively correlated with an unnamed Devonian limestone, Besa River Formation and Mattson Formation, and are interpreted to form an asymmetric, east-verging anticline-syncline fold couplet with a sub-vertical common limb. Older units west of the fault constitute a homoclinal westdipping succession consisting of (from oldest to youngest) an unnamed quartz sandstone, a diamictite and a basalt. The diamictite is a previously unrecognized unit, estimated to be at least 1800 m thick, for which we propose the name Toobally Formation. It is tentatively correlated with Ice Brook and Vreeland formations and is considered to be a glaciomarine succession in uppermost Windermere Supergroup. Overlying the Toobally Formation is an 850-m-thick succession of Neoproterozoic-Cambrian(?) basalt. The geochemistry of these basalts is consistent with rift volcanism in a within-plate tectonic setting.