110 ALASKAN MINERAL RESOURCES IN 1904. [bull. 259. 
Their age has been determined as Devonian. In the Rampart region 
and farther east and south there are black and gray shales, cherts, 
thin beds of conglomerate composed largely of chert pebbles and gray 
and black schistose, more or less graphitic grits and massive lime- 
stones. A large mass of tuffs and diabasic rocks are associated with 
these rocks in the northern portion of the region. Some of the lime- 
stones have yielded Devonian corals. In the absence of criteria for 
their separation, all of these rocks are provisionally considered as 
belonging to the Rampart formation. They form the bed rock through- 
out most of the drainage areas which have been described. 
The flanks of Lynx and Wolverine mountains are formed of black 
grits and shales. Fragments of dicotyledonous leaves were found in 
the grits, and the shales also occasionally contain obscure plant 
remains. The shales are frequently indurated, spotted, and contain 
metamorphic minerals, due probably to the intrusive granite which 
forms the summits of these mountains. Similar shales are associated 
with vitreous quartzites along the ridge that bounds the drainage area 
of Minook Creek on the east. Their separation from shales which 
belong apparently to the older formation is not easy, and all that can 
be definitely affirmed at present is that there is a formation of grits 
and shales which occupies generally the highest portions of the region 
and which is at least as young as the lower Cretaceous, and probably 
much younger. 
The general strike of the formations is northeast and east, and the 
folding has been intense. Evidence of the force which has been at 
work is afforded by quartzite and limestone breccias. 
Sandstones and conglomerates, with associated coal, occur in the 
lower valley of Minook Creek and along the Yukon, and these have 
been considered as members of the Kenai formation. The gravels of 
the high bench are probably of Pleistocene age. 
IGNEOUS ROCKS. 
Igneous rocks are present in abundance. Granitic and monzonitic 
intrusives form a large portion of the two highest peaks, and the rocks 
throughout the region are cut by numerous small dikes of granite, 
diabase, and intermediate types. The most extensive mass of igneous 
material is found in the northern portion of the region, where thJ 
lower valleys of Little Minook and Hunter creeks and the ridge 
to the south of Rampart are composed mostly of diabasic rocks and 
associated tuffs. Basalt and associated volcanics occur on Minook 
Creek below the mouth of Hunter Creek and also opposite the mouth 
of Little Minook Creek. 
