782 H. S. WASHINGTON DECCAN SALTS AND PLATEAU BASALTS 



free -and olivine-bearing modes, although the former seem to be much the 

 more common. Through the kindness of Dr. Fred E. Wright, who vis- 

 ited Iceland in 1909, I was able to study several specimens collected by 

 him. Three of these were analyzed. Of the two older basalts, one is 

 from Allamannagja, near Thingvellir, and is probably post-Glacial, while 

 the other, from Reykjavik, is pre-Glacial; a third is from a modern flow 

 of Hecla. The first two are medium gray, rather rough basalts, with 

 many small (not over 1 millimeter) phenocrysts of feldspar; the Hecla 

 specimen is a gray-black, densely aphanitic and without phenocrysts. 

 One of Holmes' (analyzed) specimens, from Grunda Fjord, in the south- 

 west peninsula, of Quaternary age, shows small phenocrysts of olivine, 

 bat none of feldspar; another, from Holmatindur, on the Eski-fjord (east 

 Iceland), would seem to represent the Tertiary plateau flows, and is a 

 dense, quite aphyric basalt of a dark gray color. 



In thin section my three specimens are much alike. They are com- 

 posed almost wholly of thin tables of rather calcic labradorite and sub- 

 ophitic anhedra or ophitic patches of an almost colorless or slightly green- 

 ish brown augite, which Holmes determined to be enstatite-augite. There 

 are rare and small crystals of olivine and apatite, but neither magnetite 

 nor ilmenite is visible in my sections. All of them carry considerable 

 colorless, very dusty glass, the Hecla specimen in most abundance. The 

 specimens analyzed by Harwood for Holmes are much the same, except 

 that they contain a few olivine phenocrysts and considerable ilmenite, 

 but either little or no glass. We see, therefore, the same relation between 

 "ores" and glass that was observed in the basalts of the Deccan and Ore- 

 gon regions. The Eski-fjord basalt of Holmes contains about 1 per cent 

 of calcite, which he regards as primary. 



In Table V are given the analyses of my three specimens, with others 

 of Icelandic basalts. 



