3
1.2
Sources and Components of Marine Sediments
Most of the sediment transported to the coastline by the rivers today is deposited on protected
coastal zones, in large estuaries, and on the
shelves; only a rather small proportion of the sediment is transported beyond the shelf edge and
reaches the bottom of the deep sea. The geographical distribution of the particulate discharge
varies greatly worldwide, depending on the geographical distribution of the respective rivers,
amount and concentration of the suspended material. According to Milliman and Syvitski (1992), the
amount of suspension load is essentially a function of the surface area and the relief of the
catchment region, and only secondarily does it
depend on the climate and the water mass of the
rivers. Apart from these influences, others like human activity, climate, and geological conditions
are the essential factors for river systems in
southeast Asia.
The southeast Asian rivers of China, Bangla
Desh, India, and Pakistan that drain the high
mountain region of the Himalayan, and the rivers
of the western Pacific islands (Fig. 1.2), transport
just about one half of the global suspension load
discharged to the ocean annually. This must naturally also exert an effect on the sedimentation
rates in the adjoining oceanic region of the IndoPacific.
Sediment transport by icebergs which calve
from glaciers and inland ice into the ocean at polar
and subpolar latitudes is an important process for
the discharge and dispersal of weathered coarse
grained terrigenous material over vast distances.
Due to the prevailing frost weathering in nival
climate regions, the sedimentary material which is
entrained by and transported by the ice is hardly
altered chemically. Owing to the passive transport
via glaciers the particles are hardly rounded and
hardly sorted in fractions, instead, they comprise
the whole spectrum of possible grain sizes, from
meter thick boulders down to the clay-size
fraction.
As they drift with the oceanic currents, melting
icebergs are able to disperse weathered terrigenous material over the oceans. In the southern
hemisphere, icebergs drift from Antarctica north to
40°S. In the Arctic, the iceberg-mediated transport
is limited to the Atlantic Ocean; here, icebergs
drift southwards to 45°N, which is about the
latitude of Newfoundland. Coarse components
released in the process of disintegration and melting leave behind “ice rafted detritus” (IRD), or
Fig. 1.2 Magnitude of annual particulate sediment discharge of the world’s major rivers. The huge amount of sediment
discharge in southeast Asia and the western Pacific islands is due to high relief, catchment, precipitation and human
activity (Hillier 1995).
1.2
Sources and Components of Marine Sediments
Most of the sediment transported to the coastline by the rivers today is deposited on protected
coastal zones, in large estuaries, and on the
shelves; only a rather small proportion of the sediment is transported beyond the shelf edge and
reaches the bottom of the deep sea. The geographical distribution of the particulate discharge
varies greatly worldwide, depending on the geographical distribution of the respective rivers,
amount and concentration of the suspended material. According to Milliman and Syvitski (1992), the
amount of suspension load is essentially a function of the surface area and the relief of the
catchment region, and only secondarily does it
depend on the climate and the water mass of the
rivers. Apart from these influences, others like human activity, climate, and geological conditions
are the essential factors for river systems in
southeast Asia.
The southeast Asian rivers of China, Bangla
Desh, India, and Pakistan that drain the high
mountain region of the Himalayan, and the rivers
of the western Pacific islands (Fig. 1.2), transport
just about one half of the global suspension load
discharged to the ocean annually. This must naturally also exert an effect on the sedimentation
rates in the adjoining oceanic region of the IndoPacific.
Sediment transport by icebergs which calve
from glaciers and inland ice into the ocean at polar
and subpolar latitudes is an important process for
the discharge and dispersal of weathered coarse
grained terrigenous material over vast distances.
Due to the prevailing frost weathering in nival
climate regions, the sedimentary material which is
entrained by and transported by the ice is hardly
altered chemically. Owing to the passive transport
via glaciers the particles are hardly rounded and
hardly sorted in fractions, instead, they comprise
the whole spectrum of possible grain sizes, from
meter thick boulders down to the clay-size
fraction.
As they drift with the oceanic currents, melting
icebergs are able to disperse weathered terrigenous material over the oceans. In the southern
hemisphere, icebergs drift from Antarctica north to
40°S. In the Arctic, the iceberg-mediated transport
is limited to the Atlantic Ocean; here, icebergs
drift southwards to 45°N, which is about the
latitude of Newfoundland. Coarse components
released in the process of disintegration and melting leave behind “ice rafted detritus” (IRD), or
Fig. 1.2 Magnitude of annual particulate sediment discharge of the world’s major rivers. The huge amount of sediment
discharge in southeast Asia and the western Pacific islands is due to high relief, catchment, precipitation and human
activity (Hillier 1995).