704 



E. M. KINDLE 



Cambrian ripple-marks. — Cambrian sandstone is extensively 

 exposed in a flat-topped hill 12 miles west of Ottawa, just south of 

 the intersection of the Canadian Northern and Grand Trunk rail- 

 ways. The rock is a hard, white to buffish-gray, moderately coarse 

 sandstone. It is thin-bedded, lying in strata 2-10 inches thick. 

 Some of the strata are beautifully ripple-marked.' All of the ripple- 

 marked beds and those associated with them appear to be quite 

 barren of fossils, although a Lingulepis acuminata Con. occurs 

 abundantly a little lower in the section along the railroad. Two 



Fig. I.- — Ripple-marks in Cambrian sandstone. The large slab shows the sym- 

 metrical type with low ridges and broad flat troughs; the asymmetrical type is repre- 

 sented by the small slab at the right of the picture. 



distinct types of ripple-marks occur in the highest beds exposed on 

 the hilltop. Both of these are shown in Fig. i. The type seen in 

 the smaller slab on the right of the picture is better shown in Fig. 2. 

 The ripple-marks shown on the large slab are symmetrical, the two 

 sides of the ripple ridge having the same slope or curvature. Those 

 seen on the smaller slab and in Fig. 2 are asymmetrical, the slope of 

 the ridges on one side being much steeper than that of the ridges on 

 the other side. The symmetrical ripple-marks show some features 

 in which they differ from those usually met with in sandstones. 



I I am indebted to Mr. L. D. Burling for directing my attention to these ripple- 

 marks. 



