460 J. B. WOODM'OliTH CANEY SHALES AT TALI HI XA, OKLAHOMA 



here nearly horizontal and most certainly not contorted as it is in the Talihhia 

 cut. Your criteria, therefore, do not account for this example. The raised 

 edges bordering some of the grooves in this specimen are hard to explain. The 

 only explanation that has suggested itself as possibly competent is that the 

 surficially decomposed boulder wsls covered by soft mud when some heavy mass 

 of shore-ice, studded beneath with fresher chert pebbles, plowed through the 

 cover of mud and into the soft surface of the boulder. The material thus 

 gouged out of the boulder might, under the circumstances mentioned, be pushed 

 aside under the cover of mud and be preserved in this position when the mud 

 again settled into the plowed furrow. 



"Regarding the great majority of the striated boulders seen by me in and in 

 tbe A^icinity of the Talihiua cut, I agree thoroughly with you in ascribing their 

 furrows to scratching by associated pebbles during the course of movements 

 within the contorted shale itself. The evidence favoring this conclusion, as 

 agreed on the ground by Hayes, Taff, and myself, was in several cases con- 

 clusive. But even here occasional 1 boulders bore stride that could not be satis- 

 factorily explained in this manner. Your figures 1 and 4 suggest examples of 

 the latter class. At any rate your interpretation of these instances does not 

 seem to me altogether satisfactory. Essentially the same kind of grooving 

 would have resulted if the pebbles had been embedded in the bottom of float- 

 ing ice and dragged over the rough silica-studded surface of previously 

 dropped boulders. I have frequently observed boulders in the Caney. some of 

 them 6 to 10 feet across, whose surface was studded with small projecting 

 silicified fossils that must have scratched any relatively soft limestone that 

 may have been dragged over them under the weight of a floating mass of ice. 

 They would have plowed furrows into the prominent parts of faces of the 

 moving pebble just as an iron planer cuts the projections off the mass of 

 evenly moving steel as they come into contact witli the stationary cutting 

 tool." 



liKMARKS ON UlUICII's COMMENTS 



As to the striated grooves in figures 1 and 4, wJiich appear from their 

 photographs to Doctor Ulrich not to be of the nature of slickensided 

 stones, it should be stated that in both cases the markings differ from 

 glacial striae in that from point to point the striated surfaces display the 

 same striation pervading for a slight depth the structure of the rock, as 

 is the case witli the incipient cleavage accompanying slickensides. This 

 seems not to me to be a characteristic of the ice striation of hard rocks, 

 such as these Ordovician limestones must have been when transported. 

 I do not see how these limestone boulders could have been softened by 

 decomposition without being dissolved. As for the striations on boulders 

 at other localities in Oklahoma, I have not seen the localities nor the 

 materials, and can only suppose as does Doctor Ulrich that where grooved 

 and striated stones occur in undisturbed horizontal beds that the striation 

 Avas accomplished by some form of ice action prior to the final deposition 

 of the erratics. I saw no stones in the Talihina cut which at the time 

 of my visit struck me as scratched by ice action. 



