INTERESTING LOCALITIES OF MESNAKD QUAUTZITE. 239 



be no discordance between the two schists. After a siiort iiiT(n-val of no 

 exposure the normal granite appears to the south. This is one of the 

 locahties which were cited by Rominger' as evidence of progressi\e ineta- 

 mor})hisra of the quartzite into the granite. However, taking the h)cahty 

 in connection witli otliers. it is certain that there is no such grachition, 

 but an unconforuTity between the two. The apparent transition may be 

 explained by the disintegrated character of tlie granitoid gneiss at the time 

 of the ^lesnard transgression; or the intense mashing produced bv the 

 folding at the junction of the two formations may ha\-e obliterated the 

 peblded granitic detritus, even if it existed. The mashing has transformed 

 the clastic rock into a crystalline schist, and has metamorpliosed the granite 

 into a similar-looking rock. 



In the northern part of sec. 3 the Mesnai-d quartzite may lie traced in 

 continuous exposure around the north, west, and south sides of the Archean 

 green schist, dipping away from it in all directions. Tlie exposures, there- 

 fore, constitute a westward-jilunging anticline. 



In thin section the larger masses of the ^ligisi Bluffs present the ordi- 

 nary phases of gray wacke and vitreous and clierty quartzites. However, it 

 is on the southeastern slope of this blutf that occur the kaolinic quartz- 

 schists described on p)). 226-227. It has been seen that in the field there 

 is difficulty in discriminating between the mashed fragmeutal rock and the 

 underlying gneiss. In thin section the two are separable. The most altered 

 phase of the detrital rock shows distinct rounding of the Cjuartz grains. 

 These are set in a tine-grained matrix of kaolin, sericite, and cherty quartz. 

 All distinct feldspathic detritus has disappeared. On the other hand, the 

 gneissoid granite has distinctly a granitic structure, and even where most 

 altered the feldspars, although much decomposed, may be recognized 



Lake Mary. — Noi'thwest of Lake Mary, in the SE. \ sec. 4 and the NW. J 

 sec. 9, T. 47 N., R. 25 W. (Atlas Sheet XXXVII), are found large exposures 

 of quartzite, dipping away from the granite on each side and toward each 

 other under the Kona dolomite, which appears as a westward-plunging 

 syncline. Near the corner of sees. 8, 9, 16, and 17, T. 47 N., R. 25 W., 



' The Marquette iron region, by Carl Rominger. Geol. of Michigan, Vol. IV, Part I, 1878-1880, 

 pp. 15, .52. 



