488 GEOLOGY OF CENTRAL WLSCONSIN. 



by ^4 inch; containing but little quartz. The weathert'd crust of this rock ^^^t. 

 is ji; inch thick, dark-brown outside, and pure wliite beneath, the latter due 



evidently to kaohnization 125 



8. Coarse iron-staiiud syenite (909) : close to the preceding, but not quite so 

 coarse, and having the felspar brownish from iron-staining, and more 

 abundant 80 



Total horizontal length of section 1 ,230 



Thickness of rock layers about 600 



On Island No. 7 of Tig. 19, are exposures which lie south of the end of tiiis section. 

 At the north end of the island, the rock (941) resembles No. 1 of the section, and con- 

 tains a vein of reddish felspatiiio granite 30 feet long, 1 foot wide, and having a central 

 band of white quartz, 1 inch to 2 inches wide. At the south end of the island a long, 

 low exposure shows a fine-grained, Hght-pinkish, distinctly gneissoid syenite, or syenitio 

 granite (943), which is very much more quartzose than any of the other "Wausau rocks. 

 The quartz is granular, glassy and wine-colored. The parallel grain is due to an ar- 

 rangement of the black hornblende, which stands out quite prominently against the 

 surrounding hght-colored quartz. 



At the i)oint C of Fig. 19, on the west side of the river, and near the north hne of Sec. 

 26, a large exposure shows rocks quite different from those at the falls below. The 

 main rook (915) at this place is fine-grained, dark-gray and hornblendic, having a dis- 

 tinctly parallel structure, and weathering to a light-pinlrish color. A number of heavy 

 beds of this rock are to be seen dipping 20° to 26° N. W., and striking N. 60° E., thus 

 corresponding in bedding with the rooks at the falls. Intersecting the dark-colored rock 

 are numerous small pinkish veins. In one place, on the river edge, a large, smooth 

 joint-surface shows a nearly horizontal vein 16 inches vide, the vein matter (916) being 

 composed of pink cleavable felspar and Kmpid white quartz. Cutting vertically thi-ough 

 this vein and the inclosing rock is a mass of a very fine-grained, decomposing, schistose 

 chloritio rock (917), 4 feet wide, having its lamination vertical. The lines of demarka- 

 tion between the three kinds of rock on this exposure are all very sharply defined. 



On the Jenny road, on the east side of the Wisconsin, N. hf. Sec. 24, T. 29, R. 7 E., 

 IM miles from Wausau, arc several low outcrops of a white- weathering, in places iron- 

 stained, slaty quartzite (931). On a fresh fracture this rock presents a non-crystaUine, 

 whitish aspect, and is quite hard. With a lens, a few minute felspar fcicets are seen. 

 I'ynte is present in minute cubes. Some specimens show a slight tendency to effervesce 

 m hot acid. The schistose structure is evident, the planes striking N. 85° E., and dip- 

 ping 50° N. W. 



One and a half miles further north, the same road ascends Marshall hill. AU along 

 this hillside in sections 12 and 1 are large, angular fragments of a fine-grained, gray- 

 ish, aphanitic, sUicious-schist (930). This rock is quite soft, very distinctly laminated, 

 splitting very readily across the lamination planes. Some specimens effervesce very 

 slightly on heating. 



Eastward from Wausau, on the north hne of T. 29, R. 8 E., the country rises rap- 

 idly, and is traversed by numerous low but abrupt ridges, such as are characteristic of 

 large portions of the Archsean area. No rook outcrops were noted on any of these, but 

 angular fragments of a white-weathering, porphyritic rock (929) were seen in great 

 abundance. This rock has an aphanitic, light grey, not very hard matrix, through 

 which are scattered a few felspar facets, and numerous amygdules of translucent, 

 brownish quartz, the latter reaching % inch in diameter. It was noticed most abund- 

 antly on Sec. 33, T. 29, R. 7 E. 



Westward from Wausau, in T. 29, R. 7 E., a number of outcrops occur. Near its 

 south Ime, this town is traversed by Rib river. In Sees. 21, 22, 27 and 28, there is 



