( 146 ) 
blocks ‘). The movements of the earth’s crust which are probably in 
the first instance a result of the progressive cooling of the lithosphere, 
are concentrated in these strips. It may be that for a long time they 
form submarine troughs of very varying depths, the geosynclinals, 
in which a strong sedimentation and considerable piling up of sedi¬ 
ments takes place. Only exceptionally where both the depth is very 
great and the nearest land surface remote (one can imagine this 
condition for instance when one or both of the adjoining continental 
blocks is wholly or partially submerged) oceanic abyssic sediments 
can be formed in portions of a geosynclinal. Afterwards, however, 
perhaps in consequence of this considerable sedimentation itself, the 
conditions of equilibrium of this labile strip may be changed, the 
geosynclinal may be compressed and thrust up to a mountain chain; 
the causes of these changes are still very imperfectly known, but in any 
case the study of the composition of the mountain chains themselves 
proves that before they were folded up they were geosynclinals. By 
the folding process the sediments are forced up, at whatsoever depth 
they might have been formed, and finally they may form part of high 
mountains *). Oceanic, abyssic sediments may in this way come to 
lie high above the level of the sea, and become accessible to inves¬ 
tigation. Thus in mountain chains there is theoretically nearly the 
only chance, and even that is a small one, that fossil deep-sea sediments 
come to form part of the dry land. For this reason such deposits will 
be found limited to mountain chains and be relatively rare on land, 
however widely they may be distributed at present on the bottom of 
the oceans, and certainly always have been. 
The facts hitherto known completely confirm this theory; all deep- 
sea rocks, which have so far been discovered occur in mountain 
chains or at least in geosynclinal areas. 
In the first place this applies to the Danau-formation, the largest 
continuous area of fossil deep-sea deposits which is at present known. 
Tectonically the Danau-formation forms part of the Upper Kapoewas 
mountain range (perhaps it would be better to call this now the 
Central Borneo mountain range) which extends with an east-westerly 
strike right across almost the whole of Borneo. The time when this 
important range was formed, is not yet known with certainty. Tie 
*) The relative position of continents and geosynclinals changes but very slowly 
and remains permanent during long geological periods. 
3) Verbeek believes that if the folding takes place at great depth, the UPP” 
sediments need not be folded too but may be pressed up more or less ver c ,. 
to a considerable height. In the West Indian as well as in the East n ^ 
Archipelago such movements appear to have taken place on a large scale. 
M. Verbeek, Molukken Verslag p. 816. Batavia 1908. 
