BENsoN.— Structural Features of the Margin of Australasia. 101 
Australian continental massif. Thus the unstable, flexible, or geo- 
synclinal region is compressed between the two continental massifs. Into 
his region results from these forces. 
According to the views of Volz (1899), Richthofen (1900), and Ahlburg 
(1913), there has been formed a network of obliquely-intersecting ten- 
sional fractures, because the thrusts from the two continental masses 
exerted a screw-like torsion, acting in directions not actually opposed 
one another. This is the view cited by Hobbs (1921); but the 
investigations of Wanner (1913, 1921), Molengraaff (1913, 1921), and 
Brouwer (1917, 1922) seem rather to indicate that the dislocations result 
from intense compression, with orogenic overthrusting or underthrusting at 
some depth and block-faulting at the surface, a view which is in part 
followed here. 
The Asiatic portion of the Malay Archipelago consists of Sumatra, 
Java, Borneo, and the regions between them. The Mesozoic rocks are 
generally of shallow or moderately deep-water origin throughout, though 
in central Borneo what are held to be abyssal deposits are rather 
beneath the South China Sea, which. covers a submerged peneplain 
(Molengraaff, 1921).* ^ Crust-folding was relatively small in this region 
during Tertiary times. The whole area is ri ged into a broad 
verging into a knot in the north-eastern portion of Borneo, and again 
folding occurred in Cretaceous times; the Permian, Triassic, Jurassic, 
and older Cretaceous strata are greatly disturbed, considerable over- 
thrusting having occurred, and are invaded by plutonie rocks.  Per- 
e, without any evidence of contact-metamorphism. 
i d i 
limestone, Oligocene-Miocene foraminiferal limestones, and sandstone, on 
which һе unconformably younger Miocene marls and tuffs with Pliocene 
* According to Molengraaff (op. cit.), this submergence was due to the general 
sea-level subsequent upon the melting of the extensive ice-sheets of the 
e 
more than 30 fathoms deep. In the absence of much definite information Molengraaft 
has suggested tentatively a like explanation for the Sahul Bank, which lies at about 
Professor Wanner, however, has informed the writer (22nd May, 1923) that Van 
Es's correlation of the Palaeozoic limestones of northern Sumatra with the Permian 
formation of Timor, cited in the previous paper (Benson, 1923, p. 34), is not, in his 
opinion, supported by a sufficient faunal similarity, and Fliegel's determination of 
them as Upper Carboniferous should stand. 
