408 R. M. Field — Middle Ordovician of Central 



until quite recently it was the only section within the 

 region which had been described in detail. 



A description of the section at Roaring Spring was 

 published by Butts (9) in 1916. To the Echinosphgerites 

 zone he gave the name Rodman, and divided the subja- 

 cent Stones River into two formations, Lowville and Car- 

 lim, the latter a new term proposed for the fossiliferous 

 but less pure limestone below the pure quarry-rock. He 

 also proposed the term Lemont for the upper and less 

 pure part of the Carlim. The facts derived from my 

 study of the section at Roaring Spring do not agree in 

 certain important particulars with Butts' published ac- 

 count; his faunal list is also incomplete and contains 

 certain supposedly characteristic fossils which are only 

 to be found 60 to 90 miles to the northeast. Finally, a 

 study of the Roaring Spring and Bellefonte sections 

 alone can give no adequate idea as to the paleogeography 

 of the area, or its relation to the Ordovician terranes of 

 eastern North America. 



Description axd Correlation of Sections. 



Nine stratigraphic columns are arranged on fig. 2 so 

 as to give a diagrammatic view of the thicknesses and 

 relative positions of the formations, the geographic posi- 

 tion of each section being shown by the same number on 

 the sketch-map, fig. 1. These two illustrations, together 

 with the following lithological and faunal descriptions of 

 the formations, will be used in the discussion of the 

 correlation of the sections within the given province. 

 Space does not permit me to give here the complete list 

 of the fauna, which is to be published later, and only 

 those species are mentioned below which are essential 

 horizon markers. The subject in its broadest sense is 

 the paleogeography of central Pennsylvania during Mid- 

 dle Ordovician time. 



The formations have been grouped under two main 

 divisions. This has been done for several reasons, it 

 being necessary at present only to draw attention to the 

 fact that the lithology and faunal characteristics of the 

 Salona and Coburn are decidedly different from those of 

 the subjacent Rodman, Center Hall, Valentine, Carlim 

 and Loysburg. The Bellefonte column (No. 5) is placed 

 first because it contains all of the formations from the 

 Loysburg to the Coburn, inclusive. The succeeding 



