420 Williams — Fossil Faunas and th 



eir use in 



Let us examine the validity of this assumption : Do divisions 

 of the geological column, proven by paleontologic evidence to 

 hold the same fauna, represent the same interval of time in 

 different local sections ? 



An attempt was made to test this question in the case of the 

 Catskill formation. A paper was written* in which it was 

 demonstrated by comparison of sections in various parts of 

 New York and Pennsylvania, that the sediments, which by 

 lithologic, stratigraphic and paleontologic characters may be 

 classified as a single formation, occupy a different systematic 

 position in the geological column of areas a few hundred miles 

 apart. In general, it was shown that when the time-scale is 

 measured by the marine invertebrate faunas, the Catskill 

 formation begins at the horizon of the Hamilton in the eastern 

 sections and farther west first appears at the horizon of the 

 Ithaca or Portage, and in central and western New York and 

 Pennsylvania does not appear till after the Chemung forma- 

 tion was well advanced. Nevertheless it could not be stated 

 that the Catskill formation occupies the same place with the 

 Chemung formation. For that would make the names partly 

 or wholly synonymous. 



It could not be stated that the Chemung is not antecedent 

 in time to the Catskill when the formations are transformed 

 into epochs, for that would mean that the two epochs are not 

 distinct. So long as the formational nomenclature alone is 

 used, the only way to state the facts is to say that the Catskill 

 is not a good formation on account of its irregular position in 

 the time-scale. 



In Dana's Manual, last edition, the relation of the Chemung 

 and Catskill on the basis of this interpretation is defined in the 

 words : " They (these Catskill beds) are now believed to be a 

 contemporaneous formation parallel in its deposition with that 

 of the off-shore and deeper waters of the Chemung period, or 

 Chemung and Hamilton periods, to the westward " (p. 576). 



The fact is thus clearly brought out that the Catskill as a 

 formation has as much title to recognition as the Hamilton or 

 Chemung. So long as we have but one nomenclature, it is as 

 reasonable to say that the Hamilton and Chemung belong to 

 the Catskill period, as to give the latter prior place in the list 

 of formations of the time-scale. But there are two sets of 

 facts ; and the real reason for the neglect of the Catskill 

 formation in the time-scale is that its fauna is not as definite 

 and significant as the fuller and more widespread marine 

 faunas of the Hamilton and Chemung formations. The indefi- 

 niteness in its relation to a time-scale which was demonstrated 

 for the Catskill formation, it is believed, is characteristic of all 



* The Journal of Geology, vol. ii, pp. 145-160, 1894. 



