17
of shelf mud accumulation can be distinguished
(McCave 1972, 1985): “muddy coasts, nearshore,
mid- and outer-shelf mud belts and mud blankets’
(Fig. 1.13). Mud belts depend on the amount of
discharged mud load, the prevalent tidal and/or
current system, or the distribution of the suspended sediment. Muddy coasts will preferentially
form near river mouths, whereas mid-shelf mud
belts are characteristic of regions where wave and
tidal activity are relatively lower than on the inner
or outer shelf.
Especially in delta regions where the supply
rates of terrigenous material are high – as in the
tropics – even the entire shelf might become covered with a consistent blanket of mud, although
the shelf represents a region of high energy conversion.
1.4.2
Distribution Patterns of
Deep-sea Sediments
The two most essential boundary conditions in
pelagic sedimentation are the nutrient content in
the surface water which controls biogenic productivity and by this biogenic particle production,
and the position of the calcite compensation
depth (CCD) controlling the preservation of
carbonate. The CCD, below which no calcite is
found, describes a level at which the dissolution
of biogenic carbonate is compensated for by its
supply rate. The depth of the CCD is generally
somewhere between 4 and 5 km below the surface,
however, it varies rather strongly within the three
great oceans due to differences in the water mass
and the rates of carbonate production.
Calcareous ooze and pelagic clays are the predominant deep-sea sediments in offshore regions
Spreading Center
Pacific Equatorial Bulge, 0.5 km
>1 Km
<1 Km
miles
km
0
2000
0
3 0 0 0
north pole
GLACIAL
WATER-CONTRIBUTED
DETRITAL
AUTHIGENIC
BIOGENIC
equator
south pole
C O N T IN E N T S
C O N T IN
E N T S
0 °C
20 °C
0° C
20 °C
Fig. 1.11 Sediment thickness to acoustic basement in the world ocean (from Berger 1974).
Fig. 1.12 Latitudinal distribution of sedimentary facies
of the shallow marine environment of continental
shelves in an idealized ocean. Bold arrows = cold water;
light arrows = warm water; grey arrows = upwelling water
(modified from Reineck and Singh 1973).
1.4
Global Patterns of Sediment Distribution
of shelf mud accumulation can be distinguished
(McCave 1972, 1985): “muddy coasts, nearshore,
mid- and outer-shelf mud belts and mud blankets’
(Fig. 1.13). Mud belts depend on the amount of
discharged mud load, the prevalent tidal and/or
current system, or the distribution of the suspended sediment. Muddy coasts will preferentially
form near river mouths, whereas mid-shelf mud
belts are characteristic of regions where wave and
tidal activity are relatively lower than on the inner
or outer shelf.
Especially in delta regions where the supply
rates of terrigenous material are high – as in the
tropics – even the entire shelf might become covered with a consistent blanket of mud, although
the shelf represents a region of high energy conversion.
1.4.2
Distribution Patterns of
Deep-sea Sediments
The two most essential boundary conditions in
pelagic sedimentation are the nutrient content in
the surface water which controls biogenic productivity and by this biogenic particle production,
and the position of the calcite compensation
depth (CCD) controlling the preservation of
carbonate. The CCD, below which no calcite is
found, describes a level at which the dissolution
of biogenic carbonate is compensated for by its
supply rate. The depth of the CCD is generally
somewhere between 4 and 5 km below the surface,
however, it varies rather strongly within the three
great oceans due to differences in the water mass
and the rates of carbonate production.
Calcareous ooze and pelagic clays are the predominant deep-sea sediments in offshore regions
Spreading Center
Pacific Equatorial Bulge, 0.5 km
>1 Km
<1 Km
miles
km
0
2000
0
3 0 0 0
north pole
GLACIAL
WATER-CONTRIBUTED
DETRITAL
AUTHIGENIC
BIOGENIC
equator
south pole
C O N T IN E N T S
C O N T IN
E N T S
0 °C
20 °C
0° C
20 °C
Fig. 1.11 Sediment thickness to acoustic basement in the world ocean (from Berger 1974).
Fig. 1.12 Latitudinal distribution of sedimentary facies
of the shallow marine environment of continental
shelves in an idealized ocean. Bold arrows = cold water;
light arrows = warm water; grey arrows = upwelling water
(modified from Reineck and Singh 1973).
1.4
Global Patterns of Sediment Distribution