60 Origin and Morphology of Ocean Margins
MUD DIAPIRS AND
SHELF. DELTA PLATFORM
GROWTH FAULTS (CREEP)
(HIGH SEDIMENTATiON RATE)
DEEP-SEA
DELTA FAN
LARGE ACTIVE
AND BURIED
SAND·FILLED
CHANNEL
SYSTEMS.
MAl LY MUD
TURBIDITES.
SOME MUD
FLOWS
CANYON
DEEP-SEA FAN
SYSTEM
UPPER FAN: SOME
SLUMPS. FLOWS OF
GRAINS. DEBRIS
AND MUD.
CHANNEL FILLS.
LOWER FAN: MAINLY
SAND TURBIDITES,
SOME CHAN EL FILLS
SLOPE APRON
SLUMPS. MUD FLOWS
PREDOMINANTLY
MUD TURBIDITES
SHELF
BREAK
SEDIMENT
ACCUMU·
LATION IN
CANYON
HEAD
SOFT AND SEMI·
EROSION
CONSOLIDATED
(STRONG
~\~~~ ~~~~~~TS, RELIEF)
AND MUD FLOWS
TRANSITION
TO HIGH AND LOW·
DENSITY TURBIDITY
CURRENTS,SAND
AND MUD TURBIDITES
ROCKFALL.
SLUMPS,AND DEBRIS
FLOWS (POLYMICT).
UNDERCUTTING OF
SLOPE BY CONTOUR
CURRENTS
Fig. 2.12. Compilation of exogenic processes shaping (passive) continental margins. [G. Einsele et
al. (eds.). Cycles and events in stratigraphy, Springer, Heidelberg, 1991: 318.]
water flowing downhill (Sect. 2.11). It is now thought that much of the sediment on
the continental rises is carried there originally by turbidity currents and by slides
starting somewhere near the shelf break, and that subsequently it is redistributed by
contour currents.
A compilation of different exogenic processes shaping the continental margin is
given in Fig. 2.12.
2.10 Submarine Canyons
The continental slope is commonly cut by various types of incisions, ravines, and
valleys, the most spectacular of which are the submarine canyons. The origin of these
impressive features (Fig. 2.13) has long puzzled marine geologists and is still a matter
of debate.
Many large submarine canyons are very much like their counterparts on land:
tributary systems in the upper parts, with meandering thalwegs (similar to river beds),
and steep sides in places (20° to 25°, even 45°). Overhanging walls also occur (Fig.
2.14). Walls may consist of hard rocks, even granite in some places. As in river