LOWER SASKATCHEWAN RIVER VALLEY. 
7 
Grand Rapids Section. 
Thickness 
feet. 
(i) Hard light grey irregularly bedded dolomite (summit near trarn- 
(h) Buff dolomite (in tramway cuts) and covered 35+ 
(g) Grey to pale buff thin- bedded, fine-textured dolomite, moderately 
hard and evenly bedded weathering to innumerable small 
rectangular blocks. These beds are cut by joints 4 to 10 feet 
apart into rectangular pillars. Fossils scarce 22 
(f) Hard light buff dolomite with coarse texture and much more 
numerous fossils than beds above. Ostracodes, Stromatopo- 
roid and Favosite corals common 4 
(e) Covered 10+ 
(d) Light buff dolomite with Conchidium decussatus very abundant 1 3 
(e) Whitish thin-bedded barren dolomite 8 
(b) Hard compact bluff limestone 1 
(a) Brecciated limestone 2 
The basal beds of this section are supposed to represent a 
horizon near the base of the Silurian as represented in this region, 
but the actual contact of the Silurian and Ordovician beds has 
not been observed in this district. The nearest exposures of 
Ordovician beds, which are known, occur 15 miles northeast of 
Grand Rapids on the shore of Lake Winnipeg south of Sturgeon 
Gill river. Cliffs of drab-coloured magnesian limestone 10 to 40 
feet high face the lake in that vicinity. The shore intervening 
between these cliffs and the base of the section at Grand Rapids 
is low and composed of glacial till and limestone shingle and 
pebbles derived from it. Just what thickness of beds may be 
between the top of the cliffs at Sturgeon Gill and the base of the 
Grand Rapids section it is impossible to state, but the relative 
position of the two sections with respect to the general strike of 
the rocks leads to the opinion that it is not very great. What- 
ever this unobserved interval may include, the earliest Silurian 
fauna at present known in the district is the Conchidium decus- 
satum fauna which occurs near the base of the Grand Rapids 
section in bed d. This large Conchidium occurs in great profu- 
sion in the thin bed to which it seems to be confined near the 
base of the section. Close examination of most of the outcrops 
on the north side of the river at Grand Rapids failed to detect 
1 This bed outcrops on the south side of the river according to Tyrrell (Ann. Rep. Cap. 
Geol. Surv.. Vol. V, 1890-91 (1893) p. 147E) This and the beds a, b, and c were not seen 
by the writer. 
