Brenson.—Structural Features of the Margin of Australasia. 103 
at any rate in Sumba, between it and the outer arc there is no evidence of 
the occurrence of Miocene overthrusting. It is overlapped by an outer 
arc which, beginning at Savu, runs through Rotti, Timor, Letti, Babber, 
alternative conceptions have been entertained by other writers. Throughout 
this whole zone very extensive crust-movements have occurred and are 
still in progress 
While Suess’ s diagram (vol. 3, p. 235) of the trend-lines of the Philippine 
and Sunda Archipelago, “ based on the writings of Drasche, Molengraaff, 
Hooze, Wichmann, Martin, Koto, and others," illustrates this ergata 
of a continuous geanticlinal ridge, he was not himself convinced of its 
correctness, for he remarks as follows (vol. 3, p. 243): “It is in itself 
scarcely probable that the cordillera which comes from Sumba and Timor 
should reappear here [in Ceram and Buru] in full development after having 
looked upon as the continuation of the d peninsula of [north- 
western] New Guinea." This view was rted in some degree by 
Boehm (1906) and lately by Gregory (1923, 19234), а and it must again be 
considered after the general structure = the Banda region as conceived 
by the Dutch geologists has been desc 
Consideration will now be given to y outer arc and the Banda Sea, 
which whole region, according to Molengraaff (1921) and Brouwer (1917, 
1922), illustrates conditions analogous to those which existed in the Alpine 
regions of Europe during Mesozoic and early Tertiary times. Brouwer’s 
(1922) most recent statement may be cited: “The tectonic features of 
the East Indian Archipelago as they now exist are the result of orogenic 
forces which have heen acting during long periods of time and have caused 
movements in a horizontal direction in many places. Where the lands 
were high above the strand-lines of the surrounding seas the ranges were 
cut down, and the deeper parts were uncovered by erosion; where at the 
same time the crust was moving below sea-level no анасы 8 took place, 
and no unconformities and disconformities in the succession of strata are 
found. The latest crustal movements are only a younger stage and a 
direct continuation of the Tertiary crustal movements. The Tertiary 
. folds and overthrusts, which were formed at relatively great depth, are 
now visible at the surface, but the fissured and faulted crust that once 
lay above them has been removed by erosion. On the other hand, the 
tectonic features due to late deformation near the earth’s surface duri 
the younger stages of mountain-building have remained visible, and are 
and overthrusts remain invisible at greater depths. In the parts of the 
earth’s crust now visible in the different islands the erosion-intervals are 
not found at the same place in the geological time-table. For the major 
tectonic features it is sufficient to describe the visible traces of two stages 
of crustal movements, the late Mesozoic and Tertiary stages, and the 
youngest stage, which still continues. The youngest stage is definitely 
known to be limited to certain parts of the present archipelago, while Ae 
distribution in time and place of the older stage is not definitely kno 
In the Alps the early Mesozoie formation and accentuation of каайн 
and synclines was succeeded in Cretaceous times by strong horizontal 
movements, which “reached their maximum in the Tertiary period. As 
