THE EASTERN AREA. 401 



III the thin scctious, upon :i clost^ cxiMiiiuiilioii, diii', pLiiiily sues that the rock is a 

 recoinposed oiie. IJiit the .niiiiiite tVii};int'iits which itiake iq) the rock are so large and 

 so clo-sely [latiked to.yethcr that one at first sight might mistake the rock for a massive 

 granite. However, tlie rounded appearance of the complex quartz-feldspar-chlorite 

 fi'agments, the presence of a few rounikHl grains of quartz and feldsp;ir ajid of a sparse 

 matrix, sliow the chistic origin of the rock. Many of the feldspar grains are broken 

 or distorted, the latter phenomenon being beautifully shown. This is probably caused 

 by i)ressnre applied after the grains were deposited in the recomposed rock. The 

 matrix consists of finely interlocking quartz, kaolin, ferrite, some carbonate and 

 chlorite. Slide 1833 contains in the groundmass a larger portion of carbonate than 

 does 4492. 



li4. Chloritic slate, from lower part of belt. Specimen 12590 (slide 5345), 155 N., 

 22.-> W , Sec. 14, T. 47 N., K. 43 W., Michigan. 



The rock is dark gray, flue grained, and finely laminated. The thin section con- 

 sists of a continuous nuiss of chlorite, ferrite, feldsjiar, quartz, sericite, or kaolin, all of 

 which are arranged in wavy lines, tlie general direction of which is parallel to the 1am- 

 i nation of the rocks. Some of the larger particles of quartz and feldspar have a deci- 

 ded clastic ai)pearance, so there is little doubt that the rock is a fragmental slate. 



2.5. Chloritic graywackeslate, from lower middle part of belt. Specimen 10397 

 (Slide 4006), 207 N., .501) W., Sec. 14, T. 47 N., R. 43 W., Michigan. 



The rock is light greenish gray, fiue grained, almost aphanitic, and is readily 

 cleavable. 



The thin section has a schistose matrix, consisting maiidy of chlorite and kaolin, 

 or hydromica, with some chlorite and gray amorphous material, in which are set small 

 Itagmeutal particles of quartz and feldspar, the latter being more abundant. 



2(». Graywackeslate, from a lower middle horizon. Specimen 12837 (slide 5490), 

 370 N., W., Sec. 14, T. 47 N., R. 43 W., Michigan. 



The rock is dark gray, medium grained, and laminated. 



Fragmental (piartz and feldspar, in grains varying from minute to those of 

 medium size, compose about one-half of the -section. The.se minerals are buried in a 

 very fine grained clay background, wliich ajipears to consist of finely crystalline cjuartz, 

 chlorite, sericite, and iron oxide. Many of the fragments of feldspar are more or less 

 altered, the resultant products being two or more of the minerals which compose the 

 l);R-kground. Calcite or other carbonate occurs as an accessory. 



27. Chloritic graywacke. Specimen 12589 (slide 5344), 500 N., 925 W., Sec. 14, 

 T. 47 N., R. 43 W., Michigan. 



The rock is greenish gray, fine grained, and massive. 



Small angular particles of quartz and feldspar compose two-thirds of the section. 

 The angularity of many of the jiarticles appears to be original, and it is ])robably due 

 to the fact that their small size has prevented rounding. A portion of them are some- 

 MON XIX 20* 



