HORIZONTAL MOVEMENT OF GEANTICLINES 561 
tion of the Malay Archipelago he distinguished two types of 
mountain-building: (1) the overthrust type of Miocene age, cul- 
minating in overthrusts of great magnitude, which was the expres- 
sion of a very powerful, but not deep-seated compression, and (2) 
the block-faulted type of Plio-Pleistocene age, consisting of ranges 
of elevated islands alternating with deep sea basins, these being 
the expression of a deeper-seated, but perhaps less energetic com- 
pression. 
It is only the vertical movements of the rows of islands that 
have been considered by these authors. In some recent publi- 
cations’ I have pointed out that: 
1. The youngest crustal movements in this region are a younger 
phase in the same process as the older and an exact continuation 
of the mid-Tertiary crustal movements. Of the mid-Tertiary 
phase we know only the folds and overthrusts which represent 
action at greater depth; of the youngest phase only the fractured 
and faulted crust which represents action near the surface; but 
the two phenomena are mutually complementary and the rows of 
uplifted islands indicate the spots where the folding process con- 
tinues at the greater depths with the same tendency to form 
overthrusts. 
2. From the outline of the rows of islands we may conclude 
that they have a large movement in a horizontal as well as in a 
vertical direction. 
The horizontal movements of the curving rows of islands are 
expressed by several of their characters. 
1. The striking fact that the Tenimber Islands and the Kei 
Islands have an outlying position in the row and both are’situated 
opposite a depression in the Sahul bank which constitutes the 
Australian continental shelf. Opposite these depressions the gean- 
ticline met with less resistance. 
=H. A. Brouwer, “On the Crustal Movements in the Region of the Curving 
Rows of Islands in the Eastern Part of the East Indian Archipelago,” Proceed. Kon. 
Akad. v. Wetensch. Amsterdam, Vol. XXII, pp. 772-82; “On Reef Caps,” ibid., Vol. 
XXI, pp. 816-26; “Fractures and Faults near the Surface of Moving Geanticlines,” 
ibid., Vol. XXIII, pp. 570-76; ‘Uber Gebirgsbildung und Vulkanismus in den 
Molukken,” Geol. Rundschau, 1917, p. 197; ‘‘Uber die horizontale Bewegung der 
Inselreihen in den Molukken,”’ Nachr. d. Gesellsch. der Wiss. su Gottingen, 1920. 
