NO. 5 PRE-DEVONIAN PALEOZOIC FORMATIONS 261 



Dr. John A. Allan gives a somewhat greater thickness to the 

 formations* (second column), which is probably more accurate, but 

 these are possibly merely more careful estimates. I did not measure 

 the formations above the base of the Devonian as I began the section 

 at that horizon. 



The lower member of the Devonian caps the eastward- facing points 

 between the south fork of Ghost River and the cliffs a few miles 

 north of the Canyon of Ghost River. This member is about 400 feet 

 (121. 9 m.) thick and formed of a coarse, dark, lead-colored, massive- 

 bedded limestone in which occur many corals and Stromatoporoid 

 forms. 



The basal bed of Devonian limestone is about 8 feet (2.4 m.) thick 

 and rests on the slightly undulating surface of the buff-colored, slabby, 

 magnesian limestone beneath ; it is filled with irregularly globular 

 masses of a Stromatopora-like organism varying in size from i cm. 

 to 10 cm. Four feet ( 1.2 m.) above this bed, there is a second Stronia- 

 topora bed about 5 feet ( 1.5 m.) thick ; in places the two beds merge, 

 forming a bed 10 to 16 feet (3 to 4.9 m.) thick. 



Similar beds are repeated higher up in the section several times, 

 and there are also layers of finer limestone filled with slender stems 

 of corals, a few gastropods, and often many specimens of Atrypa 

 reticularis. These dark Ijasal beds of the Devonian retain the same 

 general character 54 miles (86.9 km.) to the northwest at the head of 

 the Clearwater River (p. 326). and at Glacier Lake Canyon, 87 miles 

 (140. km.) distant in an air line ; they usually cap the outlying cliffs of 

 most of the ridges and spurs, as the softer gray limestones and shales 

 immediately above have broken down to form a terrace at the foot 

 of cliffs formed of the upper portion of the Devonian. 



For the formation beneath the Messines on Ghost River the name 

 of the locality. Ghost River, has been proposed^ (see p. 210). 



DEVONIAN 

 Ghost River Formation 

 I. Steel-gray, fine-grained, thin-bedded, buff-weathering, 

 finely arenaceous magnesian limestone, with a few 

 layers of siliceous purple-colored shale 1 10-125 feet 

 (33-5 to 38.1 m.) from the top; bands of somewhat 

 thicker layers of the limestone occur in the central 

 portions, some of which break down in thin slabs which 

 cover the talus slopes in places. The thinner shaly and 



Feet Meters 



VjCoI. Surv. Canada, Guide Book No. 8, pi. II, Transcontinental Excursion, 

 1913, P- 169. 

 ^ Smithsonian Misc. Coll., Vol. 67, No. 6, 1923, p. 463. 



