Page:The Journal of geology (IA journalofgeology21894univers).pdf/167

On the assumption, which has been the common practice up to the present time, that the divisions of the time-scale and of the list of formations are synonymous, it is reasonable to insist that the Catskill and the Chemung are not correlative terms, and that, in case we apply them as formation names, the one must succeed the other, but I think we all know that this is not the case. We know, that is, that in western New York a continuous section takes us through Hamilton, Portage, Chemung, Conglomerate and Carboniferous formations;^[1] that a like section in the meridian of Cayuga Lake takes us through Hamilton, an interval filled with Spirifer levis beds, the Ithaca group and 600 feet with Portage fauna, then the Chemung, the Catskill, and finally the Carboniferous. Farther east the interval between the Hamilton and Chemung is filled by rocks with an advanced stage of the Hamilton fauna; then the Oneonta and next rocks with another stage of the Hamilton fauna, then the Chemung and the Catskill. Still farther east, Chemung drops out from the series; and if we go on to Maine and Eastern New Brunswick, the Hamilton also falls out, and a long series with the latest marine fauna an Eodevonian Oriskany fauna, separated from the Carboniferous deposits by several thousand feet of deposits which, faunally and structurally, may be considered equivalent to the Catskill of New York. It is evident, thus, that at different localities the Catskill formation has a time value in one place equivalent to the closing part of the Chemung formation; at another place to the whole of the Chemung; at another to the upper part of the Chemung, and also an earlier stage during the formations of the Ithaca formation; at another place it represents the whole upper Devonian, and, if we mean to extend the use of the name to Maine, to the whole of the upper, middle, and most of the lower Devonian.

It is, therefore, clearly inappropriate to use the term Catskill as a name in the time-scale, because it has no common definition in that scale. It is an appropriate local formation name for deposits succeeding Hamilton or Chemung formations in Eastern