534 C. SCHUCHERT SILURIAN FORMATIONS 



Ingen 7 also for a time regarded the Shawangunk as of Salinan time, 

 though in 1910 he returns to the older view of their Medinan age. Paul 

 Billingsley 8 likewise refers the Shawangunk to the "early Salina." T. C. 

 Brown 9 held that the Binnewater, High Falls (the red-beds series), and 

 Shawangunk constitute a sequence "of a normal marine transgression" 

 and are of Salinan time. Finally, Clarke and Buedemann, 10 on the evi- 

 dence of the eurypterids, placed the Shawangunk in the Salinan series 

 and correlated the formation with the basal member, the Pittsford shale. 

 It was Van Ingen who was the first to return to the older view that the 

 quartzites and conglomerates are of Medina age. On December 27, 1910, 

 he presented at the Pittsburgh meeting of the Geological Society of 

 America a paper entitled "The Shawangunk grit and its facial relation- 

 ships," stating that he had found Arthrophycus at a number of places; 

 and, further, that the Clinton shales overlie the beds with the burrows. 

 This paper is not yet published, and though at the time of presentation 

 it excited considerable unfavorable comment, Van Ingen was correct. In 

 the following year 11 he abstracts his views as follows : The Clinton iron 

 ores in passing from west to east "change in shoreward directions to 

 hematitic sandstones of much greater thickness and finally to red and 

 olive quartzites, which are equivalents of part of the Shawangunk grit 

 of the northeastern Appalachians. The conclusion is reached that the 

 Shawangunk grit is of Medina-Clinton-Xiagaran age, and all older than 

 the Salina to which it has lately been referred." 



THE MEDINA SERIES 



The Shawangunk formation is usually a gray to whitish or slightly 

 greenish, cleanly washed, thin and thick bedded quartzite that is more or 

 less zonally conglomeratic. The pebbles are fairly well rounded, usually 

 of vein quartz, and as a rule under half an inch in diameter, though at 

 times and always at the base of the formation they may attain to 6 inches 

 across. Toward the top the formation may have one or more zones of 

 slightly reddish color, and these seem to be equivalent to the iron-ore 

 zones of the Clinton formation that are typically developed deeper in the 

 trough and farther away from the shore. The shale partings of the 

 Shawangunk are usually insignificant in thickness, though at times there 

 are many, and single beds may exceed 2 feet, and are either green or 

 black (carbonaceous) in color. In general the Shawangunk tends to be- 

 come more shaly in the upper half. When Arthrophycus is present, it 



7 Science, May 21, 1909, p. 830. 



8 Ibid., July 22, 1910, p. 125. 



8 Amer. Jour. Sci. (4), vol. 37, 1914, p. 474. 



"> Mem. N. Y. State Mus., vol. 14, 1912, pp. 91, 93. 



11 Science, June 9, 1911, p. 905. 



