162 COPPER-BEARING ROCKS OF LAKE SUPERIOR. 
stones, ranging from the Niagara above to a sandstone below, which, in 
common with many preceding geologists, I regard as belonging with the 
fossiliferous Cambrian sandstone that forms the base of the Paleozoic 
column of the Mississippi. At Marquette the older granites and schists 
come out to the lake, and from here to Keweenaw Bay form the country 
immediately back of the coast, leaving in front, however, a narrow band of 
the flat-lying sandstone just mentioned. 
The most eastern exposure of the Keweenawan rocks of the South 
Shore is found inthe isolated reef known as Stannard’s Rock, lying forty-three 
miles N. 94° E. from Marquette and twenty-nine miles from the eastern end 
of Keweenaw Point. Keweenaw Point is formed of the same rocks, which, 
as already explained, stretch from here westward continuously into the State 
of Minnesota. They form the south shore of the lake as far as the Montreal 
River, beyond which to the head of the lake they are bordered along the 
immediate coast by a newer horizontal sandstone, but spread over a great 
width in the northern part of Wisconsin. 
From Keweenaw Point to the Montreal River the Keweenawan rocks 
dip northward toward the lake. West of the Montreal they form two belts; a 
more southern one—the continuation of the Keweenaw Point belt—in which 
the northern dip is retained, and a northern one in which the dip is to the 
south. These two belts form the opposite sides of a synclinal trough, which 
has its western termination in the Snake and Kettle River district of Min- 
nesota, where the two belts are found uniting. Beyond the neighborhood of 
Snake River, the Keweenawan rocks do not extend to the westward, older 
formations taking their place. 
In the detailed descriptions of this chapter I find it convenient to divide 
the region traversed by the Keweenawan rocks into several districts, which 
are considered in order from east to west. 
The mining region of Keweenaw Point serves as the best point of 
departure for these more especially local descriptions, since it has been so 
long known in geological literature, and so thoroughly opened up by mining 
enterprise. The exposures here are often large, and, for the most part, the 
structure is easily read. This district, too, embraces the only portions of 
the entire extent of the Keweenaw Series that have been subjected to 
