396 



INDEX TO- THE STRATIGRAPHY OF NORTH AMERICA. 



that collections obtained from the Porcupine below the Upper Ramparts, including 

 both faunas and floras, indicate an early or basal Mississippian horizon, and Girty 

 regards it as possible that the whole of Mississippian time is represented. In the 

 Upper Ramparts, 40 miles east of the lower stations, is a belt of Carboniferous 

 rocks which Girty regards as upper Carboniferous (Pennsylvanian) . 



B 3. CAPE LISBUBNE AND CAPE THOMPSON, NOBTHWESTEBN ALASKA. 



The Lisburne formation, once considered to be Devonian, has been shown 

 to be Carboniferous by Collier,"' who collected fossils and measured the following 

 section : 



Section of Paleozoic rocTcs in Cape Lisburne region, Alaska. 



Probably the oldest formation of the region consists of heavy calcareous sandstones and 

 interbedded calcareous slates, which occur on the west side of the Lisburne Hills, where they 

 form the sea cliffs for about 15 miles north of Marryat Inlet, and are exposed for about 10 milea 

 along Kukpuk River. The heavy sandstones range in thickness from 1 ito 10 feet each, while 

 the slaty beds are usually thinner. The massive members often present schistose phases and 

 contain secondary mica. The total thickness has not been determined, though it is certainly 

 not less than 1,000 feet. * * * 



The age of the formation is inferred from its relations to the Carboniferous beds which 

 overlie it with apparent conformity, though no direct paleontologic evidence could be obtained. 

 It is certainly older than the Lower Carboniferous and is tentatively placed in the Devo- 

 nian. * * * 



The Carboniferous rocks lie east of the area of sandstones and slates just described and 

 constitute the mass of the Lisburne Hills. * * * 



The contact of these rocks with the supposed Devonian sandstones and slates has been 

 observed at three localities. In two of these localities situated north and south the relation 

 seems to be conformable, while in the third, 2 miles farther south of Cape Dyer, the contact 

 is a well-defined thrust fault, with the sandstone overlying. 



* * * The general area of undifferentiated Carboniferous * * * includes a diver- 

 sity of rocks. Along the coast, where the observations were in more detail, three formations 

 are differentiated, as follows: (1) A lower formation, consisting of slates, shales, and lime- 

 stones, containing several coal beds and jdelding Paleozoic fossil plants. (2) Overlying the 

 coal-bearing beds are black cherts, slates, shales, and cherty limestones containing corals and 

 bivalve fossils, the most common being several species of Aviculopecten. (3) Above these 

 beds is a great thickness of massive limestones, largely made up of coral interbedded with 

 massive white cherts. 



