328 THE PENOKEE lEON-BEARING SERIES, 



The thin section differs from that of 55 only in that its matrix and the contained 

 crystals of magnetite are both somewhat coarser. 



57. Chloritic graywacke, from a lower middle horizon. Specimens 9078 (slide 

 2778); 9079 (slide 2779), N. to 100 N., W., Sec. 36, T. 46 N., R. 1 E., Wisconsin. 



The rocks are like 52 and 53. 



As in 52, 53, and 54, in thin section, fragmental particles of quartz and feldspar 

 compose a large portion of the rocks. The quartz grains are usually enlarged. 

 The feldspars comprise both orthoclase and plagioclase and are frequently quite 

 fresh. The abundant matrices consist of finely crystalling quartz, of chlorite, of seri- 

 cite or kaolin, and of opaque brown or black ferrite. In a few jjlaces small flakes of 

 biotite are seen. In fragmental material and sihceous paste, as in other paBticulars, 

 these rocks are typical graywackes. 



58. Chloritic graywacke, from a middle horizon. Specimen 9077 (slides 3296 

 and 3377), 700 N., W., Sec. 36, T. 46 N., R. 1 E., Wisconsin. 



The rock is like 57. 



The thin section is like those of 67. 



Section between the east range line of R. 1 E., Wisconsin, and the iccst branch of the 



Montreal. 



59. Chloritic graywackes, from a middle horizon. Specimens 9068 (slide 2922), 

 1115 N., 1560 W., Sec. 28; 9066 (slide 2889), 1040 N., 160 W., Sec. 29, T. 46 N., R. 2 

 E., Wisconsin. 



The specimens are almost exactly like 54. 



The thin sections in no essential points difler from that of 54. 



60. Chloritic graywackes, from an upper middle horizon. Specimens 9071 

 (slide 3295), 1380 N., 180 W.; 9072 (slide 2890), 1400 N., 605 W., Sec. 29, T. 46 N., R. 

 2 E., Wisconsin. 



The rocks resemble closely the previously described graywackes. 



The thin sections are in essential particulars like the chloritic graywackes pre- 

 viously described. The fragmental grains of quartz are always distinctly enlarged. 

 While many of the feldspar areas are (|uite fresh, others are badly kaolinized ainl 

 chloritized. The al)undant matrix is of the same composition as in the previous 

 chloritic graywackes. It, however, contiiins a little biotite and nuiscoviie. Here and 

 there are black opaque areas which appear to be ferrite, but which uuiy contain 

 pyrite or carbonaceous material. 



61. Chloritic graywacke, from an upper middle horizon. Specimen 9070 (slide 

 4415), 1950 N., 1540 W., Sec. 28, T. 46 N., R. 2 E., Wisconsin. 



The rock is precisely like 60. 



The thin section is rather finer grained than that of 6(t; otherwise it is like it. 



