190 MICHIGAN ACADEMY OP SCIENCE. 



spar. Olivine seems to have been frequently present bnt is generally 

 altered. There also occur masses of more silicions rock, felsites and 

 rhyolites. Usually one sheet is directl}' piled on another, but occasionally 

 the igneous activity which poured them forth paused long enough to 

 allow the formation of a small l)ed of sandstone or conglomerate. 

 ToAvard the upper part of the formation as the igneous activil.\' died (mt. 

 the sandstones and conglomerates become more and more im])ortant until 

 tinally the top of the formation is almost entirely com})osed of red sand- 

 stone and shale. This is found on the south side of Isle Koyal and on 

 the south shore of Lake Superior west of Portage Lake. So much was 

 early settled. Two or three points remain the subject of controversy 

 and one of them is not yet settled. 



We have said that the top of the formation is a red sandstone. Is 

 this the same as or immediately beneath and earlier than the red sand- 

 stone which occurs around the east end of Lake SuiJcrior as the base of 

 its Paleozoic there, and is of the Upper Cambrian Age, or is it separ- 

 ated by a long interval of time and unconformity, so that for it an age 

 should be carved out beneath the ( "ambrian, to which the term Algonkian 

 should be applied? To this question, no positive answer can yet be given. 

 It remains for the future to decide and no fossils have been found or 

 are likelv to be found in such a great series of sandstone. On litho- 

 logical grounds these sandstones have been given ages all the way from 

 the New Ked, down. The Minnesota Geologists attribute them to the 

 Cambrian. The U. S. Geologists to the Algonkian. The Ui)per Kewee- 

 nawan diflers in a more basic character, a somewhat greater induration 

 and, judging from the Freda Well, in salty water from the typical Pots- 

 dam or Lake Superior Sandstone. But on the other hand, the tendency 

 to approach the Lake Superior Sandstone, both in lithological char- 

 acter and in structural conditions as we ascend in the Copper Bearing 

 Series, is well nmrked. We have a great outpour of igneous rock beneath, 

 a concomitant dei)ressiou, the igneous activity dies out but the depression 

 continues, and those parts of the igneous rocks which were exposed to 

 erosion or eroded and form a sandstone. This epoch of de]»ression 

 seems to continue until the Avhole 1)asin is swathed in sandstone, which 

 is represent(Ml by the Lake Su})ei-ior Sandstone. It is not to be ex]»e(ted 

 thai the uj)per part of this sandstone would contain so much trace of 

 the igneous rocks. Now. when we find the upper part of the Kewee- 

 nawan re])resenting a dejtression and we find the upper part of the 

 Cambrian also rei)resenting an era of dei)ression, whicli might well be 

 the continuation of the same, is there any good reason for supi)osing an 

 era of time to intervene which shall represent at least the middle and 

 lower Cambrian? Before we can fairly estimate Ihe argument for the 

 affirmative we must consider the second great (juestion around which 

 discussion so far the Copper Bearing Kocks are concerned has turned. 

 The relations of the Keweenawan C<)]>per Kange to the rocks flanking in 

 on the north are very simple. The beds all dip the same way and while 

 there are minor unconformities, such as will be expecte<l in a series of 

 igneous rocks and is indicated by the pebbles and the conglomerate, still 

 there a])pears to be no great break. On the south side of the Range, 

 however, the relations are much more complex. There are two or three 

 places where sandstone distinctly laps over onto the ui)tui-ned edges of 

 the Coj)per IJearing Rocks. There are other jtlaces. notably Douglass 



