84 REVIEWS 



the fragmental base of the Keweenawan, although certain igneous rocks 

 which antedate it and which perhaps are contemporaneous with the 

 upper portions of the Animikie are also called Keweenawan. The con- 

 glomerate is found at Grand Portage Island, at Isle Royale, on the 

 Baptism River, at Little Marais, on Manitou River, at the deep well at 

 Short Line Park near Duluth, and at New Ulm. 



Above this conglomerate are conglomerates and sandstones of 

 Keweenawan age which are stratified with lavas of diabasic nature. 

 Still higher up the eruptive rocks become less in quantity and the 

 fragmental rock is a sandstone, known as the Hinckley sandstone, 

 quarried in the gorge of the Kettle River in Pine county. This in 

 turn grades up into typical Upper Cambrian sandstones of the St. 

 Croix valley. The term Potsdam is restricted to the Puckwunge con- 

 glomerate and the hardened quartzites immediately overlying it, 

 represented by the Sioux quartzite, the Baraboo and Barron county 

 quartzites of Wisconsin, the quartzite at Grand Portage Island, and 

 west of Grand Portage village, the New Ulm quartzite in Cottonwood 

 county, and the quartzite in Pipestone county. 



The igneous rocks of the Keweenawan vary in age from the late 

 Animikie time to the top of the Keweenawan series. They are 

 divided into two groups, the Cabotian or Lower Keweenawan, and the 

 Manitou or Upper Keweenawan. 



The Cabotian division includes gabbro and contemporaneous red 

 rock and their surface lavas, and all other dikes and sills which are 

 associated with, but younger than, the Animikie clastic rocks, and 

 which are older than the Puckwunge conglomerate. The lower mem- 

 ber of the Cabotian is the gabbro, which covers an enormous area. It 

 extends on the east to East Greenwood Lake in T. 64, N., R. 2 E. 

 On the north it is bounded by the^Animikie strata of the Mesabi iron 

 range. Its westernmost exposure is in the vicinity of Short Line Park, 

 Duluth. The southern limit is irregular, swinging from East Green- 

 wood Lake in a zigzag manner through T. 63 N., R. 1 W., T. 62 N., 

 R. 2 W., T. 62 N., R. 4 W., T. 60 N., R. 6 W., T. 60 N., R. 7 W., 

 T. 58 N., R. 10 W., and T. 55 N., R. n W., to Duluth. 



Along the northern and northwestern side of the great gabbro 

 mass, the gabbro is plainly intrusive on the older formations, Animikie 

 and Keewatin. 



From the northern border of the gabbro many sills offshoot and 

 penetrate the Animikie strata parallel to the bedding. These are 

 known as the Loaran sills. 



