ANTARCTIC BENTHOS
5
complex topography mentioned by Brodie occur off the Antarctic
Peninsula, forming the southern limb of the Scotia Ridge, off the
Balleney Islands-Scott Island area, and in 70°E, in the form of the
Kerguelen Ridge. Outside the continental slope the sea floor extends as
broad ridges or deep basins. Essentially three main basins are involved,
an Atlantic-Indian-Antarctic Basin, an Eastern Indian-Antarctic
Basin, and a Pacific-Antarctic Basin. All three basins are cut off to
one extent or another to the north by major ridges arranged more or
less in a circumpolar fashion, whose crests lie in depths of less than
3 000 m.
Andriashev (1965) has described the peculiar nature of the Antarctic continental shelf, commenting on the " sunken " nature with an
edge a t 400-500 m or more, and the presence within the shelf limits of
" innershelf depressions " and narrow trenches which may reach
depths of 1 000 m or more.
The bottom sediments in Antarctic seas are influenced primarily by
the fact that practically all the effective transport of terrigenous
material is by ice, The effect of glacial deposits carried by ice will
extend to the northern limit of pack ice, although the intensity of effect
must diminish from the continental boundaries outwards. Glacial sediments do dominate almost to the limits of pack ice. This is not a
uniform sediment, ranging as it does from fine muds to large boulders.
There are areas such as those in which thick belts of sedentary organisms occur where sedimentation for one reason or another must be
minimal, and others such as deposits of barnacle plates (Bullivant,
1967) where the fine sediments appear to be swept away by bottom
currents.
A t its northern boundary the glacial deposit gives way to a zone of
diatom ooze, some 1 000-2 000 km wide. Diatoms occur plentifully
enough to the south but the amount of terrigenous material available
effectively masks the deposit. The northern limits of the zone of
diatom ooze extends somewhat north of the Antarctic Convergence
where diatom production is replaced by Foraminifera and Globigerina
ooze takes over. Within the zone of Diatom ooze there can be extensive
areas influenced by local volcanic action.
A . The Antarctic biological region
For those who like order in all things, it is unfortunate that the
Antarctic Continent cannot be confined within the Antarctic Circle
instead of buIging inconsiderately beyond it in several areas, and
extending the Antarctic Peninsula well beyond it to about 63"s. Some
of the benthic organisms of the Southern Ocean live in close association
5
complex topography mentioned by Brodie occur off the Antarctic
Peninsula, forming the southern limb of the Scotia Ridge, off the
Balleney Islands-Scott Island area, and in 70°E, in the form of the
Kerguelen Ridge. Outside the continental slope the sea floor extends as
broad ridges or deep basins. Essentially three main basins are involved,
an Atlantic-Indian-Antarctic Basin, an Eastern Indian-Antarctic
Basin, and a Pacific-Antarctic Basin. All three basins are cut off to
one extent or another to the north by major ridges arranged more or
less in a circumpolar fashion, whose crests lie in depths of less than
3 000 m.
Andriashev (1965) has described the peculiar nature of the Antarctic continental shelf, commenting on the " sunken " nature with an
edge a t 400-500 m or more, and the presence within the shelf limits of
" innershelf depressions " and narrow trenches which may reach
depths of 1 000 m or more.
The bottom sediments in Antarctic seas are influenced primarily by
the fact that practically all the effective transport of terrigenous
material is by ice, The effect of glacial deposits carried by ice will
extend to the northern limit of pack ice, although the intensity of effect
must diminish from the continental boundaries outwards. Glacial sediments do dominate almost to the limits of pack ice. This is not a
uniform sediment, ranging as it does from fine muds to large boulders.
There are areas such as those in which thick belts of sedentary organisms occur where sedimentation for one reason or another must be
minimal, and others such as deposits of barnacle plates (Bullivant,
1967) where the fine sediments appear to be swept away by bottom
currents.
A t its northern boundary the glacial deposit gives way to a zone of
diatom ooze, some 1 000-2 000 km wide. Diatoms occur plentifully
enough to the south but the amount of terrigenous material available
effectively masks the deposit. The northern limits of the zone of
diatom ooze extends somewhat north of the Antarctic Convergence
where diatom production is replaced by Foraminifera and Globigerina
ooze takes over. Within the zone of Diatom ooze there can be extensive
areas influenced by local volcanic action.
A . The Antarctic biological region
For those who like order in all things, it is unfortunate that the
Antarctic Continent cannot be confined within the Antarctic Circle
instead of buIging inconsiderately beyond it in several areas, and
extending the Antarctic Peninsula well beyond it to about 63"s. Some
of the benthic organisms of the Southern Ocean live in close association