SILUEIAN. 237 



age. The locality is in the Wasatch Mountains in northeastern Utah, and the same 

 section was observed in Logan Canyon, 12 miles farther north. 

 Blackwelder ^^® as a result of recent work says : 



As exposed on the crest of the range [Wasatch] there is, between the Ordovician quartzite 

 and the identifiable part of the Mississippian hmestone, a succession of dark limestones * * * 

 having a thickness of 1,000 to 1,500 feet. In the lowest beds there are corals such as Halysites 

 and Favosites. At a shghtly higher horizon there are abundant shells which Kindle thinks are 

 the same as his Pentamerus fauna of the Bear Eiver Range. 



J-K 17-18. EASTERN NEW YORK, NEW JERSEY, PENNSYLVANIA, AND MARYLAND. 



Grabau ^** describes the Silurian of New York and its relations to other sec- 

 tions in part as follows : 



The following divisions of the New York Niagaran are in common use as the North American 

 standard: Guelph, Lockport, Rochester, Clinton. 



The Clinton of the best-known section, that of western New York, begins with the true 

 or Upper Medina, which, along the Niagara River, admits of a number of subdivisions, which 

 are, however, of only local significance." The total thickness is nearly 125 feet, with 25 feet 

 of white quartzose sandstone (Whirlpool sandstone) at the base and about 8 feet of a similar 

 sandstone at the top. The middle series consists of red sandstones and green and gray sand- 

 stones and shales. The red sandstones generally show eohan cross-bedding and appear to have 

 accumulated above water. The green sandstones and shales are fossiUferous. The white 

 Whirlpool sandstone exhibits beach features ^ and probably marks the advance of the sea, 

 though it is hkely that the sand was originally dune sand, as suggested by A. W. G. Wilson. 



The fossils are generally most abundant in the shales and tliin-bedded sandstones. The 

 heavy-bedded sands are either free from fossils or have only scattered shells of Lingulse. At 

 Loclqport and elsewhere some layers are crowded with gastropod shells. 



A list of fossils from the Medina follows, and Grabau continues : 



This is a Lower Siluric [lower "Upper Silurian"] fauna, and favors more especially the 

 CUnton and Rochester faunas. It is so far known only from western New York, with the excep- 

 tion of Arthrophycus harlani, which is widely distributed. In western New York this species 

 occurs at the top of a heavy-bedded unfossihferous sandstone with an eohan type of cross- 

 bedding, and just below the upper white quartzite. In east-central New York it is found at the 

 base of the Oneida conglomerate, which is the approximate equivalent of the upper white sand- 

 stone of Niagara. In the Appalachians it is found mostly in the upper part of the Tuscarora and 

 Clinch sandstones, the stratigraphic equivalent of the Medina. * * * 



The Tuscarora has a thickness of 820 feet in Logan's Gap, Jack's Mountain, Mifflin County, 

 Pa., but thias perceptibly westward and southward, being 400 to 500 feet thick in Bald Eagle 

 Mountain and 287 feet in WeUs Mountain and the Pennsylvania-Maryland line. This thinning 

 appears to be due to failure of the lower beds, showing a true case of nonmarine progressive 

 overlap. In New York the upper part is represented by the true Medina, which has a thickness 

 of 125 feet and begins and ends with a pure white quartz sandstone. More strictly speaking, 

 the upper white sandstone alone represents the true Tuscarora, but the lower beds, still partly 

 red, and the shales probably are the equivalent of the lower reddish sandstones and greenish 

 shales underlying the true white Tuscarora, and sometimes referred to the Upper Juniata. The 

 Oneida conglomerate of central New York, 40 feet thick, is hkewise the representative of the 

 upper part of Tuscarora, though it may have had a more local origin. * * * 



The Clinton shales succeed the Oneida conglomerate in Oneida and Herkimer counties, 

 N. Y., and the Upper Medina quartzite in western New York. In the southern Appalachians 



a See Bull. New York State Mus. No. 45, pp. 88-95. 

 b Fairchild, H. L., Am. Geologist, vol. 28, 1909. 



