7o6 



E. M. KINDLE 



the waves or currents concerned in its production. The similarity 

 in type of the Cambrian and Lake Deschenes ripple-marks shown 

 in Figs. I and 2 suggests the inference that the Cambrian im- 

 pressions probably represent the work of winds and waves of a 

 very gentle character. 



In beds which he within a very few inches of the symmetrical 

 ripple-marks which have been described occur the asymmetrical 

 ripple-mark type shown in Fig. 2. The ripple-marks in the speci- 

 men shown in Fig. 2 have a width from crest to crest of 3 inches and 



a trough depth of one-fourth inch. 

 Their lee and stoss slopes are, re- 

 spectively, 9°-i5° and 20°. These 

 ripple-marks trend about S. 35 E. 

 and present their steep sides toward 

 the northeast. Ripple-marks of this 

 type represent either a wind or water 

 current moving in a northeasterly 

 direction. An interesting feature of 

 these ripple-marks is the presence of 

 a second set of much finer and less 

 distinct ripple-marks which show 

 sometimes clearly but generally 

 faintly on the stoss slopes oi the 

 prominent ripple-marks. These sec- 

 ondary ripple-marks cross the others 

 at an angle of about 45°. If they 

 are the product of wind rather than 

 current action, they indicate a shift 

 of wind of nearly a quadrant from the position which it must have 

 maintained during the development of the larger ripple-marks. 

 At the time these Cambrian sands were deposited the nearest shore 

 of the Cambrian sea lay five or six miles to the northeast if we may 

 judge from the close proximity and relative elevation of the archean 

 rocks in the Laurentian mountains on the opposite side of the 

 Ottawa valley. The wind or current direction indicated by both 

 of these sets of ripple-marks therefore appears to indicate a general 

 on-shore direction. 



Fig. 3. — Cast from mold of 

 sand ripple-marks taken under 

 water at Aylmer, Quebec. Com- 

 pare with Fig. I. 



