. Annual Reports of the Department of the Interior for the Fiscal Year Ended June 30, 1900--Twenty-First Annual Report of the United States Geological Society. unconformity. The Upper Huronian iron-l)earingseiies has a northward monoclinal dip, varying from as low as 30° toas high as 80°. For the most of the district the dip is 60° to 70°.Superhnposed upon the northern dips is a series of transverse minorrolls which gives the various formations wavy or crenulated out-crops. Also at various places there are cross faults. The most con-spicuous of these is that at Penokee Gap, where the throw is
. Annual Reports of the Department of the Interior for the Fiscal Year Ended June 30, 1900--Twenty-First Annual Report of the United States Geological Society. unconformity. The Upper Huronian iron-l)earingseiies has a northward monoclinal dip, varying from as low as 30° toas high as 80°. For the most of the district the dip is 60° to 70°.Superhnposed upon the northern dips is a series of transverse minorrolls which gives the various formations wavy or crenulated out-crops. Also at various places there are cross faults. The most con-spicuous of these is that at Penokee Gap, where the throw is 900 feet or Tlij upper slate formation of the Penokee-Gogebic series is here called the Tyler slatf, and typical exposures of the formation are found at Tylers Fork. The irou-bearing forma-tion is c;ilkd the Ironwood formation, because the city of Ironwood is partly located upon the forma-tion and adjacent to this city are the most important mines of the district. The ciunrtz-slatc formationis called Uie Palms formation, because just south of tlie Palms mine, on the Ialins property, arenumerous typical exposures of the VAN iiisE] PENOKEE-GOGEBIC DISTRICT. 339 more. At Potato Kiver is iinothor cross fault, with a throw of at least280 feet. From faults of these magnitudes the cross faults v;ny insize to those in which the displacements are Init a few feet. Besides these cross faults, faults nearly parallel to the Ijeddingoccur. These faults have an important bearing upon the genesis ofthe ores and are discussed on pp. 344-3-18. The upper 50 feet of the(|uartz-slate member is (juartzite. This quartz-slate member below andthe upper slate member above are relatively impervious formations. IHOXWOOI) FORMATION. ^«^•^^!^V^?;, thickness, and character.—The iron-bearing forma-tion extends as a continuous belt from about 6 miles east of SundayLake, in T. 47 N., K. 44 AV., Michigan, to west of English Lake, in N., R. 4 W., Wisconsin. The iro
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