GEOLOGICAL EXPLORATIONS AND LITERATUKE— 1893. 137 



upon tlie old gneisses and gTiinites of (Cascade age, south of tlie Winthrop 

 mine, is reported. The quartzites of Teal Lake are described as proljahly 

 belonging with the Holyoke formation, because their basal portion is n thin 

 conglomerate rc-sting upon chloritic and sericitic schists that resemble cer- 

 tain of the schists in the Republic formation. This quartzite is unconforiu- 

 ably above the marl)les or dolomites of the eastern portion of the j\Iar- 

 quette district, which in turn are conformably above the Mount Mesnard 

 quartzite. There are thiis two ([uartzites here, one above and the other 

 below the marble. 



The marbles and the underlying (piartzites a})pear to l)e unconfoi-m- 

 ablv above the I\e])ublic formation, which, according to the author, includes 

 sericite-schists and green schists, and at the same time to l)e below the 

 Holyoke formation. This series of rocks is known jn-ovisionally as the 

 Mesnard formation. One oi the difficulties in determining the exact rela- 

 tions of the Mesnard rocks to the neighboring series is due to the fact that 

 there is believed to exist above the Holyoke series, and uncouformably 

 above it, another series of graywackes, quartzites, etc., which is designated 

 the Negaunee formation. The existence of the Mesnard and the Negaunee 

 formations is not proved beyond doubt, but it is thought to be probable. 



The sequence in the Marquette district is thought to lie tliat indicated 

 in the scheme publislied in Science the preceding year. 



Wadsworth, M. E. a sketch of the geology of the iron, gold, and copper 

 districts of Michigan. Ibid., pages 75-155. Dated March 2G, 1892. 



The details upon which the conclusions of the preceding article are 

 based are given in this article in the same report. 



The author begins this paper with a discussion of the means ]>y whiidi 

 the various Marquette rocks were produced, and gives a table of rock 

 classification. In these preliminary remarks he refers to the green schists 

 north of Teal Lake and those near ]\Larquette as altered or metamorphosed 

 detrital deposits, in which class he also places many of the chlorite-schists 

 of the iron mines, the griinerite-schists and mica-schists in the western 

 portion of the area, and certain ottrelite-schists near Palmer, on the Cascade 

 raug-e. 



