310 
The intrusions of South Greenland all belong to the category 
of plateau intrusions. 
CHRONOLOGICAL SEQUENCE OF 
INTRUSIVE ROCKS. 
About twenty years ago Brüccer, TEazz, Wapsworts, and 
others found that in several petrographical provinces there is 
a definite order of succession of extensive Plutonic intrusions. 
The most basic rocks are the oldest, and they are followed by 
rocks more and more acid, but Ввбесев and Wansworrn have 
also indicated as a very common exception to this rule of 
‘decreasing basicity, that nepheline-syenites are younger than 
the syenites with which they are associated. More recent 
investigations in many parts of the world have, as a rule, con- 
firmed these results’. 
The Paleozoic abyssal rocks of South Greenland conform to 
the general rule. Their order of succession is: first gabbros 
(incl. essexites), next syenites, and finally nepheline-syenites 
and granites. 
The extrusive rocks and dykes, on the other hand, show a 
sequence which is much more complicated, and the results ob- 
tained from an examination of the succession of lava flows and 
dykes from different petrographical provinces apparently can- 
1 W. С. BRÖGGER, Ueber die Bildungsgeschichte des Kristianiafjords, 1886, 
р. 75. — J. J. H. Teatı, On some Quartz-Felsites and Augite-Granites 
from the Cheviot District. Geol. Mag., dec. Ш, vol. II, 1885, р. 106. 
— J. R. Daxyns and J. Т.Н. Teazr, On the Plutonic Rocks of Ga- 
rabal Hill. Quart. Journ. Geol. Soc. vol. 48, 1892, p. 104. — M. E. 
WADSWORTH, Syenite and Gabbro in Massachusetts. Geol. Mag., dee. 
Ш, vol. II, 1885, р. 207. — For fuller references see W. С. BRÖGGER; 
Eruptivgesteine des Kristianiagebietes Il, 1895, pp. 165—181, and Ill, 
1898, pp. 345, 363. 
