204 



to eacli other. It is observed that, while the crests are not straight, but 

 more or le.ss curving in tlieir outline, they are essentially parallel. 



On Doe Run. about two miles from Brooksburg, a ripple marked lime- 

 stone is exposed in the creelv bed. over a space of a few square yards. The 

 trend of crests here is approximately N. 45° E.; wave length, thirtj^-three 

 to thirty-six inches; depth of trough, three inches; thiclcuess of limestone, 

 three to five inches. Tlie vertical distance of this series of marks below 

 the Clinton formation could not lie determined so readily as in the other 

 <?ases, since the outcropping Clinton is not found within a distance of 

 several miles. An approximate vertical distance of 380 feet below Clinton 

 Avas reckoned on the basis of an observed westerly dip of ten feet to the 

 mile of the Clinton formation in other parts of the county. 



The main facts in regard to these ripple marks are placed in tabular 

 form below. 



These Hudson limestone ripple marks are exceptional in that ripple 

 marks are unusual in limestone, lieing found in sandstones and shales 

 chiefly. They are exceptional also in the fact that they are of such large 

 size. A few inches usually measures the distance from crest to crest of 

 ripple marks. Since a ripple is a small wave, these limestone markings 

 might well be called wave marks, Avere that term not preoccupied. These 

 ripple marks indicate essentially seashore conditions during the period 

 occupied in depositing some 300 feet of Hudson x-ocks and that the condi- 

 tions finally resulting in the Cincinnati Geanticline or uplift at the close 

 of the Ordovician, had long been present. The trend of these marks from 

 N. 10° E. to X. 7.j° E'., goes far towards indicating prevailing winds from 

 the northwest or the southeast during that part of paleozoic time repi-e- 

 sented in the deposition of these rocks. 



