398 
This will hold all the more when the period of stability is preceded 
by one of diastrophism, since in that case the processes of pene- 
tration and sedimentation being invigorated, the shelf and the 
adjacent peneplain will be strongly developed *) the moment that 
the transgression of the sea sets in, resulting in optimal conditions 
for the extension of the continental shelf. 
Whereas at present in regions, far removed from each other con- 
spicuously large shelves occur, the question arises whether perhaps 
such optimal conditions for the expansion of continental shelves 
have existed in recent geological time. 
This question will be answered here in the affirmative. 
First of all the conditions for shelf-building are favourable now, 
because the Pleistocene and the Holocene are periods in which the 
processes of denudation and sedimentation (consequently also those 
of gradation and shelf-growth) are very active’), owing to the 
orogenetic movements in tertiary time, which are not yet abated in 
our time. Besides this there is one more condition that has been 
favourable to the extremely wide expansion of the present-day shelves. 
It is that after the close of the pleistocene glacial period a large 
part of the earth’s surface has been invaded by the sea. This 
transgression commenced, as appears from the above, at a moment 
that the shelves and the adjoining peneplains had already been 
strongly developed in consequence of the late-tertiary orogenetic 
movements. The object of this paper is to demonstrate, for one of 
the largest shelves of the earth, that it owes its origin to the optimal 
conditions for shelf-formation, which appeared after the close of and 
in consequence of the pleistocene glacial period. 
Influence of the pleistocene glacial period on the position of the sea-level. 
What has been the influence of the glacial period on the general 
position of the sea-level ? 
In the Pleistocene age (the so-called ice-age) the ice-caps of considerable 
thickness and extent, which then covered a vast portion of the land 
1) Isostatic upheavals of continents will, at least initially, also counteract the 
seaward accretion of shelves. The plastic movement of the continents towards the 
sea (continental creep, vide T. C. CHAMBERLIN l.c. p. 585, 1913), on the other hand, 
promotes the development of the shelves. These two factors will be neglected in 
this paper, because their influence can only be negligibly small as compared with 
other influences in the region to be discussed here, viz. the East Indian Archipelago. 
2) BARRELL in his interesting study on “Rhythms in denudation” considers the 
present time as one in the history of our Earth, in which the rate of the continental 
denudation process is very high. J. BARRELL “Rhythms and the Measurements of 
Geological Time”. Bull. of the Geol. Soc. of America XXVIII, p. 775, 1917. 
