47 



which is estimated to be 3,000 feet (900 m.) thick, grades 

 upward with apparent conformity into lower Devonian 

 limestones, the total thickness of which is about 2,000 

 feet (600 m.) These are followed in certain areas by 

 argillaceous schists and slaty limestones, and these, in 

 turn, by upper Devonian limestone of considerable thick- 

 ness. The close of the Devonian period was marked by 

 volcanic activity along this coastal belt, and lavas and 

 tuffs to an estimated thickness of about 800 feet (250 m.) 

 were laid down. During the Carboniferous period, lime- 

 stones and argillites were again formed, and volcanic 

 activity began again in upper Carboniferous times and 

 continued well into the Mesozoic era. Many of the 

 altered massive greenstones and greenstone schists date 

 from this long period. The beds of lava and ash, ejected 

 from the volcanic vents, were contemporaneous with the 

 slate beds, and because of their intimate association with 

 the sediments the volcanics are regarded as submarine 

 intrusives. Their total thickness, including the slates, is 

 estimated at 4,000 feet (1200 m.) During Mesozoic 

 times the sequence of geologic events has not been 

 definitely determined because of lack of proper evidence, 

 and geologists do not agree in their interpretation of the 

 few observed facts. The evidence is at best fragmentary, 

 and indicates that, following the deposition of Carboni- 

 ferous and early Mesozoic strata, the bedded rocks suffered 

 intense metamorphism and at the same time were highly 

 tilted and intricately folded and rendered schistose, the 

 direction of the axes of folding and of the schistosity 

 being generally southeast-northwest. Immediately follow- 

 ing this period, and possibly in part concomitant with it, 

 occurred the invasion of the Coast Range batholiths, 

 whose lines of intrusion are in a broad way parallel to the 

 schistosity and bedding planes of these older rocks. The 

 Coast Range intrusives probably began early in Jurassic 

 times, and continued either to upper Jurassic or lower 

 Cretaceous times. During the lower Cretaceous, cal- 

 careous slates were deposited, after which a period of 

 uplift and folding followed. In the early Tertiary, the 

 Kenai (Eocene) coal-bearing beds were deposited in 

 isolated local basins in this region, but they are not of 

 commercial importance. They occur only near sea level 

 and in low-lying valleys and basins practically enclosed 

 by mountains of older rocks. Flat lying Tertiary basalt 

 lava flows occur here and there and attain a thickness of 



