SEDIMENTARY ROCKS 195 



Concerning the fossils collected from these limestones farther south, 

 Doctor Kindle states: 



"The Devonian collection includes two lots which may represent a formation 

 distinct from the Salmontrout limestone. They appear to belong in a Middle 

 Devonian horizon, but the absence from these lots of any species tying them 

 to the others indicates the propriety of provisionally treating them as possibly 

 belonging to a distinct formation." 



It thus appears that the Devonian limestones in this section include the 

 Salmontrout limestone, which name is thus, as before mentioned, not 

 sufficiently comprehensive to include all the Devonian limestones along 

 the boundary. 



Devono-Ordovician Shale — Ohert series. — This series, as shown on the 

 accompanying table of formations, includes beds ranging in age from De- 

 vonian to Ordovician. Along Harrington Creek, where these beds have a 

 thickness of at least 300 feet, they directly overlie Devonian limestones, 

 and are in turn overlain by a Carboniferous shale series. Farther south, 

 however, this series is at least 600 feet in thickness, and includes De- 

 vonian, Silurian, and Ordovician members. There these beds directly 

 overlie Ordovician limestones, and are in turn overlain by Carboniferous 

 shales and by the Nation River conglomerates, sandstones, and shales. 

 Thus toward the south the shale-chert series gradually replaces, in a time 

 sense, the limestone-dolomite beds. 



This series consists dominantly of ' shales and cherts, and in places 

 thinly bedded, dark gray to black cherts are closely interbedded with gray 

 to black or bluish black, soft, friable shales. The cherts are prevailingly 

 in beds ranging in thickness from 1 to 6 inches, but are in places more 

 thinly bedded; occasionally, however, they are as much as 12 inches thick. 

 The shales are typically very thinly bedded, and with the cherts constitute 

 the most characteristic, prominent, and extensive part of this chert-shale 

 series. Occasional red shales also occur locally intercalated with the 

 darker shales and cherts. Hard, gray, quartzitic shales are also somewhat 

 extensively developed, and in places these contain sufficient iron to pro- 

 duce, when oxidized, a bright red to yellow coloration on weathered sur- 

 faces, but only rarely are these rocks red on a fresh fracture. These red- 

 dish beds decompose readily to form a red or yellowish sand or mud, 

 which is a very noticeable feature of many of the hillsides on which vege- 

 tation is lacking. Hills on which members of this shale-chert series out- 

 crop are thus generally brightly colored and characterized by well rounded 

 forms and gentle slopes. The black, grayish, yellowish, and red beds, 

 with their oxidation products, present a striking, variegated landscape. 



