MESOZOIC ROCKS, CORWIJST SERIES. 73 



The series was first examined by the writer in the low coastal bluffs near Wain- 

 wright Inlet, where the rocks consist of layers of dense, earthy-colored or dark-gray, 

 soft, impure limestone or calcareous shale, and hard, bluish gray sandstone of 

 medium grain, all interbedded with dull-bluish, softer shale. Here the land mass, 

 composed in the main of these rocks, rises about 90 feet above sea level, and presents 

 a nearly flat or very gentry undulatory surface extending as far as can be seen. 



Cape Beaufort (see PI. V) marks the southern termination of this very gently 

 undulatory or nearly flat lowland, which extends southwestward from Point Barrow, 

 and which is underlain by rocks belonging, in part at least, to the Corwin series. 

 As we near Cape Beaufort, in proceeding southward, the surface soon rises by a 

 succession of low, minor ridges, of which the cape itself is the chief. This ridge 

 is about 800 feet high, and is a portion of a warped and dissected plateau extending 

 inland to the southwest (see PI. X, C). The rocks of this plateau, though resembling 

 the Corwin series, seem distinctly more indurated and bear the stamp of greater 

 age. For this reason it is thought that they may, on further research, prove to be as 

 old as Triassic or possibly Carboniferous, especially since Carboniferous fossils are 

 reported to have been found somewhere in the region. For the present, however, 

 the Cape Beaufort rocks are regarded as part of the Corwin series. 



At Cape Beaufort the rocks consist essentially of thin-bedded, impure, gray' and 

 brown sandstone and arkose, with sometimes a little conglomeratic material contain- 

 ing lignitic plant remains. The sandstone is occasionally hardened, almost to 

 quartzite. There is also some veiy impure limestone, and some coal. 



Farther west, in the region of Cape Sabine (see PI. V and PI. X, C), considerable 

 shale is also known to occur ; and still farther west, in the region of the Corwin coal 

 mines, the rocks, as exposed in the beach bluff, are mainly soft, impure, dull-greenish, 

 gray, or brownish sandstone, shale, slate, and coal. Some more typical hard, gray 

 sandstone, however, is also present. In general, the rocks occur in thin beds, from 

 1 to 2 feet in thickness, but occasionally there are layers 4 to 8 feet thick. These 

 heavier members are usualty sandstone. 



Structure. — Excepting the tilt which the beds have received by uplift, giving 

 them a general southerly clip varying from a very low angle to -40° or more, they 

 have been but little disturbed. Some folding, however, and apparently slight fault- 

 ing have taken place. 



In the lowland near Wainwright Inlet the rocks are nearly horizontal or dip 

 very gently southeastward. At Cape Beaufort the strike is N. 25° W., with dip 

 southwestward at an angle of approximately 20°. In the region of the Corwin 

 mines the strike is N. 45° W., and the dip 36° or more southwestward. Here the 

 rocks are also cut by two systems of jointing, trending nearly at right angles. The 

 one trends nearly northeast and dips northwest at an angle of 60° to 70°, while the 



