LOWER SILURIAN. 183 



York, Canada, Northern Michigan, and Wisconsin, making, along with 

 the Primordial area, the northern portion of the area marked as Lower 

 Silurian on the map (p. 165). They also come out to view along the 

 Green Mountains, the eastern part of the Appalachians from New 

 Jersey south west ward, and in Missouri and Arkansas ; and farther 

 west, in the Rocky Mountain region. 



The beds of the Calciferous epoch consist of calcareous sandstone 

 with some magnesian limestone in Canada and Northern New York, 

 and are mainly magnesian limestones in the Mississippi basin. The 

 Quebec group consists of shales, sandstone, and thin beds of limestone 

 near Quebec ; but are of limestone chiefly in East Tennessee, and in 

 the Rocky Mountain region. It may be an upper stratum of the Cal- 

 ciferous formation. 



The Chazy — so named from a locality in Northern New York — 

 is an extensive limestone formation, occurring near the Archaean in 

 Northern New York and Canada, stretching westward north of Lake 

 Huron, and making part of the "Magnesian limestones" of Missouri. 

 It is represented by a sandstone — the "St. Peter's sandstone " — in 

 Wisconsin and Iowa. 



The crystalline limestone or "marble" of the Green Mountains has 

 been proved by fossils to include the Calciferous and Chazy, and also 

 the Trenton limestone ; and that of Eastern Pennsylvania is probably 

 of equivalent age, Chazy and other fossils having been found by Prime 

 in Lehigh County. The St. Peter's sandstone, overlying the Lower 

 Magnesian limestone of Wisconsin and Iowa, is referred to the Chazy 

 epoch. 



1. Calciferous epoch. — a. Interior Continental basin. — Tn New York and Can- 

 ada, the Calciferous formation often consists below of impure magnesian limestone of a 

 dark gray color. In many places in northern New York, the layers are very hard and 

 siliceous, and contain geodes of quartz crystals, as at Diamond Rock, Lake George, and 

 at Middleville and elsewhere in Herkimer County, etc. The mixture of calcareous with 

 hard siliceous characteristics is a striking peculiarity of the rock. Owing to the lime ' 

 present, much of it becomes rough from weathering. Besides quartz and calcite, 

 barite, celestite, gypsum and occasionally blende and anthracite, are found in its 

 cavities. The limestone often contains chert or hornstone. 



The "Lower Magnesian Limestone" of Missouri, mostly unfossiliferous, is referred 

 by Swallow to the Calciferous epoch. He makes it to consist of four limestone strata, 

 190 to 350 feet thick, which he numbers, beginning above, 1 to 4, and, between these, 

 thinner strata of sandstone, 50 to 125 feet thick. Shumard has described fossils from 

 the third which are regarded as Calciferous. In the other strata, above, the rest of the 

 Canadian period may be represented. Tn Wisconsin, according to Hall, the Lower 

 Magnesian limestone is in all only 200 to 250 feet thick; and at top there is the St. 

 Peter's sandstone, mostly 60 to 100 feet thick, referred to the Chazy. Farther north, 

 near Lake Pepin, there are, beneath the Magnesian limestones, several hundred feet of 

 sandstone, probably Calciferous in age. Along the south shore of Lake Superior, on 

 Keweenaw Point and elsewhere, there is sandstone only. On Keweenaw Point, it under- 

 lies at one or two places a thin, fossiliferous limestone of the Black River and Trenton 



