Mineralogy and Petrology. The mineral grains and rock 

 fragments were identified in a general way, using only a 

 binocular microscope. For this reason no attempt was made 

 to distinguish between the ferromagnesian minerals or, in 

 most instances, between the feldspars. The minerals and 

 rocks identified are listed in table IV. 



Of the minerals identified, quartz and feldspar are almost 

 ubiquitous. However, they are most abundant in the north 

 Bering Sea and the Chukchi Sea. Pyriboles (pyroxenes and 

 amphiboles) and olivine are most common in the south Bering 

 Sea near the volcanic rock source in the Pribilof and Aleutian 

 Islands, but they were noted also in most of the other samples. 

 Of the micas, biotite is the most common, especially in the 

 north Bering Sea and the Chukchi Sea and near Joneau, Alaska. 

 A white amphibole common in the Juneau area has been iden- 

 tified as tremolite. Noteworthy is the abundance of magnetite 

 in the snapper sample NEL 567 taken just south of Unimak 

 Island in the Aleutians. At this location, magnetite is the 

 most abundant constituent of the sand comprising the bottom. 

 As might be expected, basalt grains are common in the 

 south Bering Sea, becoming less common toward the north 

 where they are mixed with grains of granite and quartzite. 

 Volcanic glass is a common constituent in the Chukchi Sea, 

 into which it has possibly been carried by north-setting cur- 

 rents from the more volcanic areas of the Bering Sea. In 

 many of the samples taken from the Kodiak area, pumice is 

 the most prominent constituent. In the Juneau area meta- 

 morphic rock fragments and pebbles are common, including 

 slate, schist, and gneiss. 



Authigenic minerals such as glauconite and phosphorite 

 are practically absent from these sediments. This finding 

 suggests that rapid deposition is taking place on the shelves 

 of the Bering and Chukchi Seas, since such authigenic min- 

 erals tend to form under conditions of very slow or no depo- 

 sition. Unweathered mineral grains of species which are 

 subaerially unstable, such as olivine, biotite, and the pyri- 

 boles, are abundant. 



Diatoms. Diatom frustules are not abundant either as to 

 numbers or species in the bottom sediments. In all cases 

 they represent less than one per cent of the sample. The 

 identifications of the diatoms (see table V) were made by 

 Mr. Brian Boden of the Scripps Institution of Oceanography. 

 Diatoms are most abundant in the sediments of the south 

 Bering Sea and to a lesser extent in Kotzebue Sound. Cosci- 

 nodiscus centralis Ehrenberg is the dominant species, being 

 found in nearly all the samples; Coscinodiscus curvatulus 



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