6 ARCTIC BASALT PLATEAU 
all arctic countries, whereon nepheline-bearing rocks were encoun- 
tered as trachydolerite on Hare-Island and Spitsbergen, ! as trachyan- 
desite and nepheline-basanite known from Jan Mayen and Spits- 
bergen. * Associated volcanic rocks are andesites (Greenland, Ice- 
land, East Spitsbergen), rhyolites (Iceland) and an alkali-trachyte 
(Jan Mayen). Throughout all rocks with a few exceptions are equal 
in salic and femic mineral constituents, and concerning alkalies 
distinctly sodic. On nine excellent and new analyses, made by 
H. F. Harwood, the author demonstrates some detailed peculiarities 
of the region, amongst them the belt of basaltic rocks rich in tita- 
nium dioxide and stretching from Hare Island and Scoresby Sound 
over Iceland to the Faroes; on both sides of this belt the richness 
in titanium dioxide fades out, the content in feldspar increases; 
this belt appears indebted to underlying magmatic sources high in 
titanium dioxide. In conclusion the memoir contains some remarks 
on ,petrographic provinces“, the connection of which with terms 
such as Atlantic and Pacific, alkaline and calc-alkaline Holmes finds 
not suitable. He attempts to mark out the petrographic series by 
one of their characteristic members, each series being limited in 
space and time by distinct geological processes. The andesitic, 
spilitic, trachydoleritic, and tephritic series are associated the first 
with compressional and upward movements, the second with com- 
pressional and downward movements in regions of sedimentation, 
the others with differential movements of faulted blocks, a dominant ' 
uplift or subsidence in connection with depth of fusion possibly 
having significance. To all these series basalts are common foun- 
dations, and basalts alone are not sufficient to determine the series. 
The Arctic region represents two series, the andesitic and the trachy- 
doleritic, as lying between two well marked types of petrographic 
provinces, the tephritic of the Atlantic Islands, and the andesitic of 
1 These Spitsbergen rocks are described by V. M. Goldschmidt in Vidensk.- 
Selsk. i Kristiania Skrifter, math.-naturv. kl. 1911. N:o 9. 
