46 

 A. The South Shore Cliffs. 



Plates X V to XX. 



The first of these cliffs extends from the mouth of Eighteen 

 Mile Creek south-westward for a distance of about three 

 miles, beyond which a low and sandy stretch separates it 

 from the next cliff'. The northern half of this section, or that 

 portion between Eighteen Mile Creek and Pike Creek, is of 

 the greatest interest to the student, as it includes, besides all 

 the beds found in the lower gorge of Eighteen Mile Creek, a 

 number of interesting structural and dynamic phenomena, 

 which will be described below. This portion of the section 

 comprises several crescents, and as the strata dip at about 

 fortv feet to the mile, or approximately one foot in one 

 hundred and thirty,* the appearance of faults is produced, 

 wherever the central portion of the farther crescent is seen 

 directly behind the projecting salient between the two 

 adjacent crescents. 



About forty feet of the Hamilton shales are exposed in this 

 .section near the mouth of Eighteen Mile Creek. The Trilo- 

 bite beds would probably be exposed at the base of the 

 section, if the talus were removed. The other beds noted in 

 the Eighteen Mile Creek sections, can be seen in the northern 

 half of this section, when not covered by talus. The shale 

 is full of fossils, mainly brachiopods, among which 

 Spirifer mucronatus (Conrad) predominates. The shells 

 may be picked out of the weathered bank with ease, and 

 usually occur with the valves separated, so that specimens 

 showing the muscular impressions and other internal 

 features are among the frequent treasures to be met with in 

 collections from these banks. The talus is especially rich in 

 Athvris spiriferoides (Eaton). These are furnished by the 

 disintegrating concretionary layer, nine feet below the 



*This estimate is based on the fact, that at the mouth of Eighteen Mile Creek, the 

 Encrinal limestone is about forty feet above water level, while at the " uplift," a 

 little over a mile to the south, in a straight line, this rock has reached the level of 

 the lake. The inaccuracy comes from the greater actual length of the section when 

 the curves of the crescents are considered. The dip thus obtained is only the 

 apparent, and not the true dip. 



