362 HATCHER — MARINE AND NON-MARINE FORMATIONS. [April 7, 



in Washington also read it. Hatcher and I spent an evening in 

 earnest, friendly discussion, at the close of which he stated that on 

 some points he had evidently not expressed his ideas clearly, while 

 on others his views had been modified, and that he would seek 

 further criticism from some good stratigrapher and would revise his 

 manuscript thoroughly before publishing it. Evidently he never 

 found time for the revision as he did not change the manuscript in 

 any particular. 



There is certainly a lack of clearness of expression, which seems 

 to me due to confusion of ideas, in the repeated statements that 

 imply that stratigraphic sequence in undisturbed deposits does not 

 necessarily mean chronologic sequence. As an example the second 

 of Hatcher's emphasized conclusions may be quoted: *' That an 

 overlying deposit may have been contemporaneous in origin with 

 that immediately underlying it instead of more recent. ' ' Obviously 

 he did not mean to assert that in any actual exposure one stratum is 

 contemporaneous with another on which it rests, or with still 

 another above it. That would be contrary to the fundamental 

 principle of stratigraphic and historical geology, and Hatcher 

 repeatedly denied that he intended to express any such ideas. He 

 meant rather that distant exposures holding the same apparent 

 position in a formation laid down along a changing coast may not 

 be strictly contemporaneous, and that a formation may be overlain 

 or underlain by deposits similar to those formed simultaneously 

 with it in another area. Thus when he says that the Pierre shales 

 overlie the Judith River beds but are partly contemporaneous with 

 them in origin, he refers to the fact that the Pierre shales in one 

 area form an undivided marine formation which includes the 

 equivalents both of the Judith River beds and of the overlying 

 marine beds which we have designated as the Bearpaw shales. The 

 confusion is caused by calling a part of a formation by the same 

 name as the whole. 



Mr. R. T. Hill has long ago suggested that the Dakota sandstone 

 was a littoral formation laid down while the sea was trangressing the 

 land from Texas, Kansas and Nebraska to the Rocky Mountain 

 region, and that it may represent in different parts of the area a 

 much longer time interval than its thickness would indicate. The 

 same author gives a still better example in his discussion of the 

 " Basement Sands " of the Lower Cretaceous, which, he says,^ 



^ Twenty-first Anu, Rep. U. S, Geol. Survey, Pt. VII, pp. 132, 133. 



