PRE-CAMBRIAN LITERATURE OF NORTH AMERICA 653 



Animikean — i. Pink quartzite and arkose with thin beds of jasper con- 

 glomerate sim'lar to Lorrain series at Cobalt 



2. Slatelike graywacke — beautifully and thinly bedded 



3. Conglomerate, grajrwacke, slatelike graywacke, quartzite, 

 arkose 



Great unconformity 

 Algoman — Granite, massive, and at times gneissoid 



Knight^ and others report on the Abitibi-Night Hawk Gold 

 Area southeast of Cochrane on the Canadian National Railway. 

 The succession includes Keewatin rocks consisting of basic pillow 

 lavas, rhyolites, basalt, diabase, hornblende, and chlorite schists, 

 which are overlain by slate graywacke, quartzite, conglomerate, 

 and iron formation. These Keewatin rocks are intruded by 

 diabase and gabbro, peridotite and pyroxenite, granite and other 

 acid rocks, quartz diabase and olivine diabase dikes. 



In 191 1' A. C. Lawson restudied the Rainy Lake area which 

 he had reported on in 1887. In -1887, Lawson reported that the 

 pre-Cambrian rocks of this region were all Archean and that the 

 succession from the bottom upward is as follows : 



A series of clastic sediments metamorphosed to mica quartz 

 schists and paragneisses called the Coutchiching. This series is 

 conformably overlain by the Keewatin, consisting dominantly of 

 amygdaloidal and ellipsodial greenstone lava flows, chloritic 

 schists, and other basic rocks of a similar nature. The Coutchi- 

 ching and Keewatin were intruded by batholithic masses of granite 

 and granite gneisses and allied acid igneous rocks which caused 

 the doming up of the rock into which they were injected. 



The restudy of the Rainy Lake area by Lawson in 191 1 was 

 occasioned by the fact that the United States Geological Survey 

 and the International Committee of 1898 did not accept Lawson's 

 conclusion that there existed a Coutchiching series of rocks strati- 

 graphically below the Keewatin. This dissent from the opinion 

 of Lawson was based on field work by Van Hise in various parts 



' C. W. Knight, A. G. Burrows, P. E. Hopkins, and A. L. Parsons, "Abitibi- 

 Night Hawk Gold Area," Ontario Bur. Mines, 28th Ann. Kept. (1919), 84 pp., maps, 

 and illustrations. 



^ "The Archean Geology of Rainy Lake," restudied by A. C. Lawson. Canada 

 Geol. Surv. Mem. No. 40 (1913), m pp., geological map in pocket, 9 pis., i fig. 



