38o 



and shales represent the Etchemlnian. The green trachyte 

 belongs to the Coldbrookian. 



The white sandstone is a constant feature at the same 

 horizon over a great part of the whole Cambrian basin. 

 By Dr. Matthew this bed is regarded as the base of the 

 Lower Cambrian while by Dr. Walcott it is held to mark 

 the base of the Middle Cambrian as the fauna of the 

 immediately overlying beds indicates. Under this view 

 the Etcheminian is of Lower Cambrian age. By Dr. 

 Matthew the trachyte is considered to be an effusive flow 

 closely associated as regards age with the overlying Etche- 

 minian both of which formations are thought to be older 

 than the Lower Cambrian or Olenellus zone. 



Seely street follows a nearly due east course from the 

 head of Gooderich street, almost parallel with the strike 

 of the Cambrian (Acadian) measures. At the junction 

 of Seely and Prospect streets, the strata are well exposed. 

 The measures consist of dark slates alternating with harder 

 beds usually less than one inch in thickness. 



On the eastern side of the road leading north from the 

 eastern end of Seely street, are exposures of nearly vertical, 

 dark slates with thin beds of dark, fine grained sandstone. 

 To the north of these beds, the white sandstone, the base 

 of the Middle Cambrian, is exposed in a small ridge. The 

 width of the outcrop along the roadside is about 40 feet 

 (12 m.). Immediately overlying the white sandstone is a 

 dark, coarse sandstone, while underlying it are dark 

 greenish sandstones belonging to the Lower (?) Cambrian, 

 Etcheminian division. The strata dip to the south- 

 east at an angle of about 60°. The contact of the Etche- 

 minian with the underlying volcanics of the Coldbrookian 

 is not exposed along the roadside. The first exposures 

 of the underlying volcanics is a few yards north of a branch 

 road leading to the northeast. 



The basal beds of the Cambrian are only imperfectly 

 exposed along the roadside. The following section as 

 measured by Dr. Walcott in the immediate neighborhood, 

 indicates the general character of the strata. The measures 

 are tabulated in descending order, that is, in the order in 

 which they are exposed along the road from south to 

 north. 



