236 PROCEEDINGS OP THE AMERICAN ACADEMY 



Caiion of the Colorado River towards tlie west, and to Alabama and 

 Texas on the south, there are almost continuous lines of the outcrop- 

 ping of the Taconic System ; and that the only point in the south- 

 ern hemisphere where the Primordial fauna has been yet certainly 

 found is in the Argentine Republic at Salta and Jujuy. 



I must make a reservation as to the "Lake Superior sandstone" 

 and '' Keweenawan series " of eruptive rocks. Ko proof whatever, 

 pakrontological,* stratigraphical, or lithological, has been given of 

 their being of the age of the " Tonto Group " (Potsdam sandstone), or 

 of the "Grand Caiion and Chuar Series" of the Colorado River; 

 and their synchronism is merely a speculative supposition. The iden- 

 tification of those sandstones with the Potsdam of New York, which 

 was based on the discovery of a great quantity oi Ling ula prima at 

 Tequamcnon Bay, has long been given up. They came from a small 

 boulder of the glacial deposits. Dr. C. Rominger says, " There is no 

 record of any instance in which recognizable fossils were found in situ 

 in the Lake Superior sandstone." f Dr. R. V. Irving says, '' The 

 horizontal sandstone of the south shore of Lake Superior belongs 

 unquestionably to this formation (Potsdam sandstone), though it is a 

 matter of doubt whether the two sandstones do or ever did connect." J 



All the eruptive rocks, melapliyrs, and a part of the diabases and 

 porphyries containing native copper and zeolites are similar and 

 identical with the same rocks in Connecticut, Pennsylvania, and Nova 

 Scotia on this continent ; and with the rocks containing copper in 

 Tliuringia, where the}'' belong to the Kupferschiefer and Rothliegende 

 of the Dyas (Permian). If lithology has a meaning with regard to 

 tiie age of rocks, the copper-bearing rocks of Lake Superior are Dy- 

 asic, while the Lake Superior sandstone of Sault Ste. Marie, Gros 

 Cap, La Pointe, and Bois Brule River belongs to the Bunter Sand- 

 stein of the Trias. 



As to the existence of the Taconic System in the Lake Superior 

 region, it is very possible that the slates of Kakabeka Falls, and some 

 slates, conglomerates, diabases, and gabbro found on the edge and 

 even in the interior part of the ciystalline rocks forming the centre 



* Several specimens having a (lecided Orthocerniites form liavc been found in 

 the melapluT and diabase of Point Keweenaw since 1848, a fact similar to the 

 discovery of undoubted pieces of Orthoreratites in the diabase of Bohemia, and 

 this goes far to confirm tlio Post-Silurian age of the copper-bearing rocks of 

 Lake Superior. 



t Oeol. Surv. of Michigan, Vol. I. Part Til. p. 80, 1873. 



t Tiie Mineral Resources of Wisconsin, p. 11, 1880. 



