458 J. B. WOODWURTJI CANKY SIIALKS AT TALI II J N A. OKJ.AUOMA 



was discussed and the inference drawn tliat the boulders were transported 

 by floating ice. 



ITlrich/ who shared the investigation of these erratics with Taif, 

 stated his conclusion regarding the transportation of the boulders in a 

 brief footnote in 1911 as follows: 



"The assumption of locally frigid couclitions in the early Peunsylvanian is 

 based primarily on the fact that erratics of all sizes, some as much as 20 feet 

 across and 5 or 6 feet thick, occur in the Caney shale of eastern Oklahoma. 

 These were transported not less than 50 miles, and many probably were car- 

 ried much farther. No other competent means of their transportation than 

 ice — presumably heavy shore ice — has been suggested." 



The doubt expressed by Mr. Taff concerning certain of the striae and 

 a desire to compare the striated rocks with known examples of Paleozoic 

 glaciated stones led the writer, in August, 1911, to visit the most prom- 

 ising locality for striated boulders in the railroad cut northeast of the 

 hamlet of Talihina.' 



Criteria of glaciated Stoxes 



As the question at issue is the nature of the striae in certain of the 

 stones, the criteria of certain groups of stri« may first be set forth. 

 Glacial striae on rock fragments held between the bottom of a glacier 

 and the rock-floor or between that floor and a boulder through which 

 the weight of the moving ice is transmitted are typically scratched, how- 

 ever deep, by a process ifi which the material of the striated stone is 

 crushed under pressure and removed as powdered rock or fine particles. 

 In the case of consolidated rocks undergoing glacial striation the re- 

 sultant striae show no trace of flowage of the rock in the process. This 

 is for the reason that, however great the weight of the overlying ice, the 

 crushing strength of ice is less than that of the weaker consolidated 

 rocks, and the ice will yield before the pressure in the zone of striation 

 of rock fragments reaches the pressure at which the shearing and recon- 

 solidation of crushed rock particles takes place. Moreover, the ice. 

 owing to its property of flowage under pressure, readily permits the 

 crowding of the stones and boulders used as striating tools into new 

 positions. In the case of very great pressure it is held by some physicists 

 that pressure-melting of the bottom ice takes place, and consequently 

 striation at this point would cease because of the deposition of the rock- 

 matter in the subglacial zone of pressure-molten water. For these rea- 



® E. O. Ulrich : Revision of tho Pnleozoic systems. Bull. Geol. See. America, vol. 22, 

 inil, p. 352. footnote. 



^I am Indebted to Mr. Robert W. Sajies. curator of the Geological Section of the Uni- 

 versity Museum of Harvard University, for personally defraying the field expenses in- 

 curred in visiting Oklahoma. 



