THE LATE PALEOZOIC IN ALASKA 183 



company with shales, sandstones, and flows of lava that entered the sea 

 and cooled. The pyroclastic beds are composed of angular fragments of 

 rocks, little decomposed, and contrasted with the materials derived from 

 the decomposition and erosion of land-masses, carried by streams or ocean- 

 currents and deposited to form ordinary sandstone and shale. The shales 

 are black to bluish and gray. All gradations occur from typical fine-grained 

 black shale through limy shale to impure argillaceous limestone and fine 

 sandy shale to sandstone. 



In the central Copper River district, Mendenhall 1 reports Permian (?) 

 sandstone, shale, and limestone 6,000 to 7,000 feet thick, with included 

 intrusive sheets and some pyroclastics. His section is as follows: 



6,700 Black shale. 



6,000 Limestone, very fossiliferous. 



Black shale. 

 5,000 Heavy-bedded, pure-gray limestone, diabase intrusives. 



Limestone and sandstone beds, fossils. 



Dark limestone. 



Sandstone, fossils. 

 4,000 Black limestone. 



Shale. 



Gray feldspathic sandstone. 



Buff limestone. 



3,000 Thin limestone and sandstone. 

 2,000 Fossils. 



Thin sandstone and tuffs. 



Coarse tuff. 

 1,000 Greenish sandstone and shale. 



Fossils. 

 o Thin limestone. 



This section was made in an isolated mass cut off from the rest of the 

 country by a fault, but it is probably of the same Gschelian, and lower, age 

 as the Ketchikan series. Mendenhall considers this series equal to the 

 Chitistone limestone of Schrader and Spencer and the Nabesna limestone 

 of Schrader. It is very probable that the upper prevailingly calcareous 

 part is to be reckoned as Gschelian in age and the lower arenaceous and 

 tufaceous part as lower Carboniferous. 



Similar deposits are found in the Kenai Peninsula. On the headwaters 

 of the Gulkana and Susitna Rivers, Martin, Johnson, and Grant 2 and 

 Moffit 3 record Carboniferous slate, tuff quartzite, and limestone. In the 

 Hanagita-Bremmer region Moffit 4 records Carboniferous (?) schist, slate, 

 and limestone. Many beds of limestone are from 100 to 200 feet thick. 



1 Mendenhall, W. C., Geology of the Central Copper River Region, Alaska, U. S. Geological 



Survey, Professional Paper No. 41, p. 40, 1905. 

 1 Martin, G. C., B. F. Johnson, and U. S. Grant, Geology and Mineral Resources of the 



Kenai Peninsula, Alaska, U. S. Geological Survey Bull. 587, 1915- 

 * Moffit, F. H., Headwater Regions of Gulkana and Susitna Rivers, Alaska, U. S. Geological 



Survey Bull. 498, 1912. 

 4 Moffit, F. H., Geology of the Hanagita-Bremmer Region, Alaska, U. S. Geological Survey 



Bull. 576, 1914. 



