388 E. O. ULRICH REVISION OF THE PALEOZOIC SYSTEMS 



or for a new set of names in Indiana when those used in Illinois and 

 Kentucky are clearly applicable. Good names for new formations are 

 too scarce to permit such waste of material. 



THE STANDARD SECTION FOR AMERICA 



That no single region of the size of a State contains within its borders 

 sufficient data to work out a complete marine sedimentary record of even 

 a single geological period, much less of an entire era, is suggested by the 

 course of stratigraphic studies in New York. This State has been active 

 in geological matters for upwards of three-quarters of a century, and 

 more than any other in America has furnished the data upon which the 

 present pre-Waverlyan standard section is based. Although the essential 

 features of the New York section were believed to have been completely 

 worked out more than sixty years ago, it is nevertheless a fact that as a 

 result of more modern methods of research the aggregate thickness of this 

 section has been more than doubled in the past twenty-five years. This 

 was accomplished, not only by finding that the maximum thickness of 

 some of the formations is greater than had been thought, but, perhaps to 

 an equal or greater extent, by discovery of facts proving that great de- 

 posits in eastern New York are not, as had been assumed previously, 

 equivalent in age to beds in the central and western parts of the State, but 

 are really either younger or older and in whole or part new elements of 

 the geological column. And the end is not in sight. Even the best 

 known sections are under suspicion and are being revisited by geologists 

 of the State and Federal surveys in the hope that some hitherto over- 

 looked feature may be discovered. 



More disturbing than all this is the gradually growing fact that the pre- 

 Devonian part of the New York section is far less complete than had been 

 supposed. Except at a few localities to the east of Hudson River the 

 State contains no true Cambrian rocks; and even these exceptions offer 

 but an insignificant representation of this great system. The lower mid- 

 dle part of the Ozarkian is fairly well developed on the south, east, and 

 west slopes of the Adirondack uplift, but for the higher and basal parts 

 we must go to Missouri and the southern Appalachian region. As for 

 the Canadian system northeastern New York offers both the shale and 

 limestone phase in sufficient development to rival central Pennsylvania — 

 where the deposits are thicker but less fossiliferous — in supplying data 

 on which the standard for America is to be based. Our conception of 

 the Ordovician, Silurian, and Devonian systems in America is so long 

 and firmly grounded in the New York section that any attempt to intro- 

 duce another standard is likely to prove futile. Still it is necessary to go 



