6o4 FRANCIS PARKER SHEPARD 



shows either that the highest formations involved were located near 

 the end of that period, or that the lowest formations not deformed 

 belong to the next period, when the earlier record is missing. This 

 practice is unfortunate, because the evidence merely indicates that 

 the diastrophism occurred either after or before (as the case may be) 

 the deposition of the beds in question and it may have occurred 

 several periods later or previous. 



R. T. Chamberlin's account of the Paleozoic disturbances^ is 

 very accurate and a most valuable contribution to geology, but the 

 contemporaneity of the diastrophic movements, with which the 

 paper deals, are based to considerable extent on the forementioned 

 type of evidence. For example, included among the disturbances 

 said to occur at the end of the Silurian, is one in Alaska which is 

 based on the metamorphism of pre-Devonian rocks.^ Again in the 

 "Westphalo-Cardonides" deformations^ reference is made to Haug" 

 concerning certain ranges between central Siberia and South Asia. 

 Here evidence shows only that Carboniferous formations are 

 involved in the folding. Among the "Permo-Carbonides" defor- 

 mations the folding of the Russian Geosyncline^ is given. Concern- 

 ing this Suess^ shows that Permian strata are involved, but Jurassic 

 is the first formation overlying the unconformity. 



Since there appears to have been a general emergence of the 

 lands at the close of the Paleozoic, it is only natural to expect that 

 the last marine strata involved in any subsequent folding which 

 occurred before the next marine invasion should be Carboniferous 

 or Permian. Since any non-marine strata which may have been 

 deposited in the meantime would probably be unfossiliferous, these 

 would be likely to be neglected, although they might represent parts 

 of the Triassic or later periods. Thus all post-Paleozoic and pre- 

 Cretaceous deformations are likely to be called Permian. 



Another point that must be remembered is that much of the 

 evidence for the times of diastrophism is very inaccurate so far as 



' Op. cit., Vol. XXII, p. 315. 



» R. T. Chamberlin, op. cit., Vol. XXII, p. 326. 



3 Ihid., p. 340. 



4 Emile Haug, Traitede Geologie, II (191 1), 834. 



5 R. T. Chamberlin, op. cit., Vol. XXII, p. 342. 



« Ed. Suess, The Face of the Earth, SoUas Trans., Vol. I, p. 505. 



