GENERAL GEOLOGY 39 



granite cliffs at Cape Chibukak, at the west end of the 

 island, the granite being like that in Plover Bay. 1 He saw 

 this overlain by horizontal brownish or reddish stratified 

 materials, probably scoriaceous or agglomeratic. Capt. 

 Hooper and Dr. Muir report having seen volcanic cones 

 on the island. 2 



If Dr. Muir is right in the opinion that an ice-sheet 

 covered the region, the boulders of this shingle may be 

 erratics of remote origin; but according to the view of 

 Dr. Dawson and Mr. Gilbert that there has been no 

 general glaciation, the boulders are of local origin. 



Following is a list of the rocks : 



METAMORPHIC ROCKS 



(a) Dolomitic marble. A white fine-grained statuary marble, 

 slightly flamed with grey streaks, effervescing only slightly with strong 

 acid. 



(6) Marble. Clear grey fine-grained massive crystalline limestone. 



(c) Black crystalline limestone full of small spots of white crystal- 

 line limestone, mostly angular, but many seeming to be sections of 

 crinoid stems and small Chaetetes-like corals (213). The section 

 shows the presence of other, but indeterminate, fossils. 



(</) Malacolite contact rock. Kalk-silikat-hornfels (209). The 

 rock seems to be a common limestone banded regularly in white and 

 black layers about one-eighth inch thick and slightly pyritous. Under 

 the microscope it is seen to be made up of a uniform, rounded-granular 

 mass of colorless pyroxene grains (with some biotite scales), which 

 are finer in the dark layers (in which there are a few graphite grains) 

 and coarser in the white layers and in veins branching from the latter. 



A similar contact rock was found by Mr. Palache on contact of 

 tonalite and the Paleozoic limestone in Glacier Bay. It makes fine 

 blocks banded in flat black and white layers one-fourth inch thick. 



(e) Reddish-brown fine-grained micaceous rock like the darker 

 layers in d. 



(jf ) Dark grey cherty slate with white spots that seem like traces 

 of fossils (214). 



Bull. Geol. Soc. Am., vol. v, p. 138, 1894. 



2 Report of the Cruise of the Corwin, 1881, pp. 33, 140, 1884. 



