446 HISTORICAL GEOLOGY. 



Murray refers to the Huronian also diorytes, slates, quartzytes, and conglomerates, that 

 occur in the peninsula of Avalon, southeastern Newfoundland, and describes, from the 

 upper division, a fossil of uncertain relations which he names Aspidella Terra-novica, and 

 also a worm burrow referred to the genus Arenicolites. The gneisses of the region he 

 calls Laurentian. 



The structure and relations of the Huronian along the iron-bearing belt from Mar- 

 quette to Penokee in Wisconsin (including the Penokee-Gogebic range, and the Menominee 

 iron region) have been studied with care by Irving and Van Hise. Van Hise and Pumpelly 

 have recognized a subdivision of the Huronian north and south of the lakes, on the ground 

 of a stratigraphical break, into Upper and Lower Huronian. 



In most cases, kinds of rock have had chief importance in the subdivision of the 

 Archaean. T. S. Hunt proposed the division of the Archaean (commencing below) into 

 Laurentian, Norian, Arvonian (of Hicks), Huronian, Montalban, Taconian. The Montal- 

 ban includes the White Mountain micaceous gneiss ; and the Taconian, the rocks of the 

 Taconic series now known to be of Paleozoic age. C. H. Hitchcock in his Report on the 

 geology of New Hampshire, adopts the subdivisions, beginning below : Laurentian, Mon- 

 talban (or Atlantic, including granites, gneisses, etc.), Labradorian, and Huronian. A. C. 

 Lawson, from his Canada studies about the Lake of the Woods, Rainy Lake, and else- 

 where, has divided the terranes above the Laurentian into the Coutchiching (mica schists 

 and gneisses) and Keewatin (thinner schists with conglomerates and some iron ore), and 

 to the two united he has given the name Ontarian ; the term Huronian is not used. 

 A. Winchell arranges the Marquette iron region below the true Huronian in a group called 

 the Marquettian. The Laurentian Gneissic group underneath is made 88,000 feet thick. 

 N. H. Winchell refers the original Huronian beds on the north shore of Lake Superior 

 to the Lower Cambrian ; and makes the Archaean of Minnesota to include three divisions : 

 (1) the Laurentian gneiss and related rocks ; (2) the Vermilion schists, partly hornblendic 

 schists (equivalent to the Coutchiching of Lawson) ; (3) the Keewatin schists, which are 

 iron-bearing. The Animikie beds, consisting of chlorite schist, slates, sandstones, and 

 small beds of iron ore, having in general small dip, have been referred to the Huronian by 

 Logan, Irving, and Van Hise, but to the Cambrian by Selwyn, Winchell, and others ; and 

 Selwyn has announced the discovery in it of markings which, according to G. F. Matthew, 

 are tracks much like tlie tracks of an animal found in the Middle Cambrian of St. John, 

 New Brunswick. The Mesabi Range with its large beds of iron ore is made Cambrian 

 by Winchell. The Archaean rocks of central Texas are divided by T. B. Comstock 

 (1890) into the Burnetan and Fernandian, corresponding apparently to the Laurentian 

 and Huronian. The latter section is described as containing large beds of magnetite. 

 Overlying beds in which no fossils have been found he calls Eparchaean. M. E. Wads- 

 worth has announced (1892) the following subdivisions of the Archaean in northern 

 Michigan : (1) Cascade, (2) Republic, (3) Mesnard, (4) Holyoke, and (5) Negaunee 

 formations ; 2 and 3 corresponding to the Lower Marquette, and 4 and 5 to the Upper. 



Van Hise, in 1893, proposed to restrict the term Laurentian to granite-gneisses — a 

 petrological distinction ; and gave to a supposed second division of the Archaean, the 

 term Mareniscan, derived from the name of a township in Michigan. 



A bibliography of the American Archaean to 1884, with various notes, is contained in 

 the " Azoic System," by Whitney and Wadsworth, pages 331-566 of vol. vii. of the Bull, 

 Mus. Comp. Zool., Cambridge, 1886. A full bibliography, coming down to 1892, is pub- 

 lished in the Report on the " Archaean and Algonkian," by C. R. Van Hise (1892), con- 

 stituting Bulletin No. 86 of the U. S. Geol. Survey. The latter work contains brief 

 abstracts of the publications noticed, a full exposition of the views entertained, and the 

 author's own conclusions at length. The distinguishing characteristics of the subdivisions 

 proposed by Hunt, Lawson, and others are given in this Report with much fullness ; and 

 all investigators of Archaean terranes should have a copy of it at hand. The subject is in 

 an unsettled state, with wide divergences in opinion among investigators. 



