( 145 ) 
Hitherto not so keen attention has generally been paid to fossil, 
oceanic, abyssic deposits * *) as might have been expected, considering 
that they indicate one of the most extreme situations into which a 
portion of the surface of the lithosphere can be brought, and considering 
that 40 % of the bottom of all oceans on earth consist of such 
deposits, which are still formed there continually. 
Probably this is caused by the fact that such sediments have as 
yet been found in a fossil condition as rocks in but very few places 
under such conditions as permitting of their character as abyssic sedi¬ 
ments being established beyond controversy ’). This is again intelligible 
if we bear in mind that only under very special conditions deposits 
formed at a depth of more than 5000 meters below the surface of 
the sea, can be lifted so high as to form part of the dry land and 
become accessible to investigation. Theoretically the only chance of 
this occurs in mountain chains where sediments, formed at widely 
different depths, can be forced up by folding to a great height above 
sea-level. 
The conviction that the earth’s crust consists of parts of widely 
different stability, is gaining more and more ground. The more stable 
portions form extensive blocks which apparently can only change 
their position relative to each other and to sea-level by very slow 
upward and downward vertical movements. Haug 3 ) calls these stable 
blocks, whether situated above or below sea-level, aires continentales 
or simply continents. If they are situated above sea-level the formation 
of deep-sea deposits is excluded a priori, and if they are situated 
below the level of the sea, oceanic deep-sea deposits may be formed 
in case the depth of the sea is sufficiently great, but they have a 
very small chance indeed to get accessible to investigation. 
The more mobile portions of the earth’s crust, the geosynclinal 
areas, separate in broader or narrower strips the stable continental 
even in case they were deposited in abysmal depths. I personally doubt whether 
climatic changes could bring out such a radical change and consider the explana¬ 
tion given in the next pages for the possible cause of the paucity of fossil, oceanic, 
abyssic, siliceous sediments more likely. 
*) Their very existence is even doubted by one of the leading text-books where 
it is only admitted for Barbados. 0. Krummel. Handbuch der Oceanographie, p. 211. 
1907. 
2 ) For this a large area of distribution is necessary in the first place, because 
locally Radiolian rocks can be formed, which are not originated from abyssic sediments. 
Limestone containing Radiolaria e g. may be locally changed into Radiolarite through 
silicification and destruction of all organisms with calcareous tests. 
s ) Em. Haug. Les geosynclinaux et les aires continentales. Bull, de la Soc. G6ol. 
de France. 3. XXXVIII. p. 617. 1900 and Traite de geologie I. p. 157. 1907. 
