PALEOZOIC ROCKS, FICKETT SERIES. 69 



the top of Fork Peak the grit and quartzite give way to dark schistose slate and 

 dark-gray micaceous sandstone. 



Southward, at a geologically higher horizon, gray sandstone, limestone, gray 

 schist, some quartzitic schist, slate, and conglomerate are encountered. These rocks 

 are medium layered, variously interbedded, and more or less sheared. In the region 

 of Hunt Fork a dark-gray or bluish schistose sandstone and soft slate become 

 predominant. Apparently ascending in the column, still farther southward, the 

 rocks become for the most part very tine-grained gray or bluish quartz-schist, with 

 finally greenish chloritic schist and slate, which continues to the southern edge of 

 the series, where it rests unconformably on the Skajit limestone formation. The 

 quartzitic schist and the green chloritic schist often carry considerable quartz in 

 small veins and stringers, trending more or less parallel with the schistosity and 

 the bedding. But exceptions occur, as shown in PL XI, A, where a species of 

 gash veining breaks across the bedding. This quartz frequently is most abundant 

 in the bights of sharp folds and along lines of strain and breaking. So far as 

 observed, the veins carry no valuable metals. 



Besides the above-noted rocks, light-gray and dark or black limestones, appar- 

 ently belongiug to the series, but not met in place along the route traversed, were 

 sighted and studied with the field glass both southeast and southwest of Fork Peak. 

 These limestones, judging from the resemblance to the specimens found in the 

 stream gravels, are the mother rocks of the fossils occurring so abundantly in 

 the streams. Their position in the geologic section seems to be above the con- 

 glomerate, grit, and quartzite portion of the section and near the dark schistose 

 slate and dark-gray micaceous sandstone, as shown to some extent in PI. VII. 



Structure. —The Fickett series, like the other Paleozoics of the range, has been 

 subjected to faulting and folding, incident to mountain building. The general 

 structure, however, seems to be monoclinal, with strike and trend east and west and 

 dip south at angles of 20° to 45°. The dip may vary, however, from southeast 

 in some localities to southwest in others, while in certain cases the rocks lie nearly 

 horizontal or dip very gently north. The prevailing southerly dip of the series as 

 a whole seems to point to a greater and probably later elevation in the northern 

 than in the southern part of the range since the Fickett was laid down. 



The series is finely cut in some localities by the major nearly northeast-south- 

 west jointing, whose planes are frequently slickensided and usually dip 70° to 

 80° NW. Slight movement, or normal faulting, has frequently taken place along 

 them. The rocks are also traversed by a secondary set of joints, trending nearly 

 northwest and southeast, with dip nearly vertical, or in some instances 60° to 

 80° SW. 



The schists, and notably the slates, often exhibit excellent cleavages, a good 



