HATDEN.] GEOLOGY MOEAINAL DEPOSITS. 59 



long ridges, tlie surface being covered over with fragments of limestone, 

 sandstone, and pudding-stone. About four miles below the divide the 

 little stream cuts through a high ridge. On the south side the ridge is 

 composed largely of laminated trachyte, inclining to the northwest at 

 an angle of 60^. While on the north side the rock is more compact, 

 hard, and full of masses of quartz, as if the old granite had been turned 

 to a somber gray by the heat of the igneous rocks ; this mass, which is 

 very conspicuous and rises 800 feet or more above the little stream, ap- 

 pears very distinctly stratified, and inclines 60° northeast, while the 

 limestone-beds dip northwest 30° to 60°. This is a most complicated 

 piece of geological work, which would require more time than any of 

 the party could devote to it to work it out in detail, though the report 

 of Dr. Pealeis more complete. "We believe that the igneous rocks have 

 been pushed up from beneath the overlying quartzites and limestones 

 in the form of dikes, along a line trending about northeast and south- 

 west. The peculiar bedding of the trachyte is so regular that it gives 

 them strikingly the appearance of stratified rocks. There are several 

 ridges nearly parallel which present somewhat the form of an anticlinal, 

 the felstone porphyries being lifted up so that they present their basset 

 edges opposite the outcropping edges of the limestone and quartzites ; 

 thus one side of the anticlinal is composed of igneous rocks, and the 

 opposite side of sedimentary. Between the porphyritic rocks and the 

 limestones there is quite a wide interval, 400 or 500 feet, worn out by the 

 action of water, and covered with debris, but underneath are the up- 

 turned edges of quartzites, pudding-stones, and sandstones. The strike 

 of the limestones is about southeast, with a dip northwest 60°. The 

 limestones are 150 feet thick, and filled with corals, Productus, and other 

 forms, which indicate Carboniferous age ; the whole standing up like a 

 massive wall 300 feet high. On the outer side of the wall comes 400 or 

 500 feet of soft sand, reddish-yellow and brown, with some harder lay- 

 ers of sandstone, inclining at the same angle, but worn down low, and 

 covered with grass. Then comes another bed of trachyte, with the 

 layers forming a synclinal with the Carboniferous limestones. Between 

 the two trachytic ridges deep side- gorges are worn down to the stream 

 that has cut its channel through all the ridges at right angles. About 

 two miles farther, near the junction of the little stream that flows from 

 the foot of Italian Peak, on the east side, the reddish sandstones occur 

 with layers of a coarse conglomerate, made up of well-worn pebbles of 

 limestone and quartzites, much like the conglomerate seen near Mount 

 Garfield, in Montana. I think there is here an example of a great fault, 

 where the old Silurian quartzites and limestones have been lifted by a 

 force acting vertically, so that the strata are horizontal, while the 

 younger beds. Carboniferous and Triassic, are inclined from the west 

 side at an angle 60° to 80°. The valley is full of detrital matter, and at 

 one point the stream cuts through a sort of moraine, showing a section 

 of 60 feet on either side composed of gravel and huge bowlders much 

 worn, while high up on the sides of the hills bordering the valley this 

 drift conceals to a great extent the basis-rocks. The rather rounded 

 wooded ridge on the west side of the branch is covered with the debris 

 of the trachyte, which shows that the dikes penetrated the crust 

 everywhere. The sedimentary rocks crop out here and there, so that 

 we can infer their existence. Sometimes only the quartzites are left, 

 and the igneous material has been poured over them : again, on the 

 Carboniferous limestones, or the red sandstones of the Triassic, or even 

 the black clays of the Cretaceous. All these formations crop out from 

 beneath the trachytes in the vicinity. 



