AND ARCHJ^AN ERA. 



287 



Utah.* The quantity of iron found in these strata is far greater than 

 in any other. It may well be called the Age of Iron. 



The above figures show the contortion of the strata (Fig. 259), and 

 the mode of occurrence of the iron (Figs. 260, 261). 



Area in North America. — 1. These strata cover the greater portion 

 of Labrador and Canada, and then, turning northwestward, extend to 

 an unknown distance, but probably to the Arctic Ocean. The area forms 

 a broad V, within the arms of which is inclosed Hudson's Bay. It may 

 be seen on map, p. 291. This is the most extensive area known on the 

 continent. 2. On the eastern slopes of the Appalachian chain un- 

 doubted patches are found as far south as Virginia, and a larger area 

 in this region is referred with much probability to the same. This is 

 shown on map, p. 291. Its further extension southward along the 

 chain is still doubtful, though probable. 3. In the Rocky Mountain 

 region extensive lines and areas of outcrop are known, trending in the 

 general direction of the chain, and forming the axis of the great ranges. 

 4. Several small patches are also found scattered about in the basin of 

 the Mississippi, apparently exposed by erosion. 



Doubtless the Laurentian rocks are far more extended, but covered 

 and concealed by other and later rocks. The area mentioned is the 

 area of surface-exposure. It represents so much of Archaean sea-bot- 

 tom as was subsequently raised into land, and not afterward again 

 covered by sediments ; or, if so covered, again exposed by erosion. 



Physical Geography of Archaean Times. — As these are stratified 

 rocks, they must have been formed from the debris of still older rocks 

 forming the land of that time. But as they are the oldest known rocks, 

 we know nothing of the position of the land from which they were 

 formed. But since, during the rest of the geological history, the con- 

 tinent has developed from the north toward the south, it seems most 

 probable that this earliest land lay still farther north, perhaps in the 

 North Atlantic region, and disappeared when the Laurentian area was 

 elevated into land. 



* Newberry, Genesis of Iron-Ores, School of Mines Quarterly, 1S80. 



