ALGAE, BELIEVED TO BE ARCHEAN 



JOHN W. GRUNER^ 

 University of Minnesota, Minneapolis, Minnesota 



During recent years attention has been called to the wide- 

 spread occurrence of fossils in Huronian rocks.^ These fossils are 

 mainly algae, although bacteria,^ including iron bacteria,'' have 

 been found. The work on the origin of the iron-bearing formations 

 of northeastern Minnesota led the writer to a close examination, 

 not only of the Huronian cherts, but also of the Archean Soudan 

 formation and the overlying conglomerates.^ The discovery of 

 micro-organisms in chert pebbles at the base of the Pokegama 

 quartzite (Upper Huronian) of the Mesabi range^ encouraged the 

 search for organisms in still older conglomerates. This resulted 

 in the finding of fossil algae in pebbles of the Ogishke conglomerate. 



The Ogishke conglomerate is the lowest formation of Huronian 

 age north of Lake Superior, and overlies directly the Archean 

 basement complex. It is highly folded and metamorphosed. The 

 pebbles in it include all the varieties of rocks found in the Archean 



' Published by permission of Dr. W. H. Emmons, director, Minnesota Geological 

 Survey. 



^ C. D. Walcott, " Pre-Cambrian Algonkian Algal Flora," Smiths. Inst. Misc. 

 Coll., Vol. LXIV, No. 2, 1914; ihid., "Notes on Fossils from Limestone of Steeprock 

 Lake, Ontario," Geol. Stirv. Canada, Mem. 28, 1912, p. 16; E. S. Moore, "The Iron 

 Formation on Belcher Islands, Hudson Bay, etc.," Jour. Geol., Vol. XXIV (1918), 

 pp. 412-38; Grout and Broderick, "Organic Structures in the Biwabik Iron-bearing 

 Formation of the Huronian in Minnesota," Anier. Jour. Sci., Vol. XLVIII (1919), 

 p. 199. 



3 C. D. Walcott, "Discovery of Algonkian Bacteria," Proc. Nat. Acad. Set., Vol. I, 

 (1915), p. 256. 



"•J. W. Gruner, "The Origin of Sedimentary Iron Formations: The Biwabik 

 Formation of the Mesabi Range," Econ. Geol., Vol. XVII (1922), p. 418. 



5 N. H. Winchell, "Geology of Minnesota," Geol. Nat. Hist. Surv., Vol. IV (1899), 

 p. 282; J. M. Clements, "The VermUion Iron-bearing District of Minnesota," U.S. 

 Geol. Surv., Mon. 45, 1903, p. 274; C. R. Van Hise and C. K. Leith, "The Geology of 

 the Lake Superior Region," U.S. Geol. Surv., Mon. 52, 191 1, p. 129. 



^ J. W. Gruner, op. cit., p. 420. 



146 



