196 



PALEOZOIC TIME. 



The Stockbridge limestone formation (Eolian limestone of Hitchcock) varies in thick- 

 ness from 1,000 to probably 3,000 feet. In Mt. Eolus, East Dorset, Vt., the thickness 

 is 2,000 feet. The upper part of this formation is doubtless Trenton, though its lower 

 portion is referred to the Chazy epoch of the Canadian period. 



(b.) Interior Continental basin. — The Galena or lead-bearing limestone, of Wisconsin 

 and the adjoining States in the West, constitutes the upper portion of the Trenton 

 series, and often alternates with layers of the Trenton limestone. Its color is light gray 

 or yellowish. It is generally magnesian limestone. It is 100 to 200 feet thick in north- 

 ern Illinois; about 250 feet thick near Dubuque, Iowa, and the underlying Trenton 20 

 to 100 feet (Hall). There is usually at base a buff-colored limestone, equivalent to the 

 Black River group. 



In Missouri, there are 350 feet of limestone, the upper 100 called Receptaculite lime- 

 stone by Shumard. 



In East Tennessee, the formation includes blue limestone, with many fossils, 200 to 

 600 feet thick; and, above, 380 feet of red and gray marble, 400 of bluish shale, and 

 250 of iron-limestone containing the Asaphus Platycephalus. In Middle Tennessee, 

 where the beds are horizontal, there are from 400 to 450 feet of blue limestone (Safford). 



(c.) Arctic region. — The Trenton limestone*has been identified upon King William's 

 Island, North Somerset and Boothia. 



2. Utica Epoch — (a.) Interior Continental basin. — The Utica shale is 15 to 35 

 feet thick at Glenn's Falls, in New York; 250 feet in Montgomery County; 300 in 

 Lewis County ; 300 near Quebec. 



(b.) Appalachian region. — In Pennsylvania, the rock is a black shale, and in some 

 parts it is fossiliferous. The thickness, given by Professor Rogers, in the Kittatinny, 

 Nippenose, and Nittany valleys is 300 feet, and in the Kishacoquillas valley 400 feet. 



3. Hudson River Epoch. — The Hudson River shales cover the region north of 

 Lake Champlain, in Canada, reaching to Quebec, and northeastward to Montmorency 

 and beyond. They also lie over a small area near the centre of the Trenton limestone 

 region of the Ottawa basin. 



In New York, the Hudson River beds include shales and sandstones. They are the 

 Lorraine shales of Jefferson County (the Pulaski shales of the New York Annual Re- 

 ports), containing some thin beds of limestone. The slates along the Hudson River 

 were referred to the Quebec group by Logan, but are now proved to be mainly of this 

 group. 



The thickness of the shales, in Schoharie County, N. Y., is 700 feet; near Quebec, 

 2,000 feet; in western Canada, 700 feet; on Lake Huron, 180 feet; in the Michigan 

 Peninsula, 18 feet; in Iowa, 25 to 100 feet. In Missouri, there are alternations of shale 

 and sandstone, with some limestone, 100 to 200 feet in total thickness; at Cincinnati, 

 shales and limestones, 700 feet thick. In Middle Tennessee, the Cincinnati series in- 

 cludes the Nashville group of Safford, and consists of argillaceous limestone, with 

 many shaly layers, about 500 feet thick. In East Tennessee, the beds (corresponding 

 to both the Utica and Hudson River epochs) are of great extent, and consist of blue 

 calcareous and more or less sandy shales, with some thin layers of calcareous sand- 

 stone. They also occur of great thickness in Virginia, and reach down to Alabama. 



In Pennsylvania, in the Kishicoquillas valley, the rock is a blue shale and slate, with 

 some thin layers of calcareous sandstone, and the thickness is 1,200 feet; in the Nittany 

 valley, 700 feet; in the Nippenose valley, a little less. (Rogers.) 



The limestone formation on the island of Anticosti has a total thickness of nearly 

 2,400 feet, and is divided by Logan into five parts — the first, or lowest, 959 feet thick; 

 the second, about 300 feet thick; the third, about 450 feet; the fourth, about 550 feet; 

 the fifth, 70 feet. The first two are referred to the Trenton period, and the rest to the 

 Upper Silurian. There are thin beds of shales in the series. The rocks are nearly 

 horizontal. 



