The Mississippi delta is the greatest source of sediment to the Gulf of Mexico, although there are a
number of minor rivers in Texas. Here sediment transport takes place along the coast from east to west.
Because the active part of the Mississippi delta lies
as far east as it does today, less sediment arrives at the
Texas coast. The fact that this coastline is subsiding at
the same time leads to transgression of the coastline.
This example shows that if the supply of sediment due
to strike feeding cannot match subsidence, the result
will be a transgression.
2.36 The Shore Zone
The shore zone is where land and sea meet, and we can
distinguish between different types:
1. Rocky Beach. The beach is covered with pebbles
and blocks or solid rock representing ancient, resistant bedrock. Much of the coast of Norway is of this
type, but only 2% of the coastline of North America. Rocky beaches form in areas which have been
uplifted tectonically, and where the coast erodes
metamorphic or eruptive rocks.
2. Sand or Gravel Beach. This is the most common
form of beach zone where we have active sedimentation or erosion of older sediments (makes up 33%
of the coastline of North America).
3. Barrier Island. This is a beach which is separated
from the main coastline by a lagoon. Common in
North America (22%), but less common in other
areas.
4. Muddy Coastlines. Beach zones which consist basically of clay are formed where we have sediments
with a very low sand content, and where there is
little wave activity to wash out or enrich any sand
the sediments might contain. We find this in parts
of clay-rich deltas and estuaries and where there is
abundant vegetation along the beach zone which
protects the clay sediments against erosion (e.g.
mangrove forest).
5. Cheniers are isolated sandy beach ridges on coastal
mud flats. They are abundant along the coastline
around major deltas like the Mississippi and the
Amazon. They require low tidal ranges, moderate
Mediterranean
Sea
Port Said
Cairo
0
10
20 km
Scale
B r a n c h )
Ni le
(Da nie tta
L a k e
M a n z a la
Alexandria
Distributary channel facies
Coastal barrier - strand plain
Coastal basin
Coastal lowlands (salt marsh-alkali flat)
Delta plain
Shelf and prodelta
L a k e b u ru ll u s
L a k e ld k u
N i l e
(R os et ta br an ch )
L a k e M a ry o f
Fig. 2.38 The Nile delta system is an example of a wave-dominated, destructive delta system. (Fisher et al. 1974)
76
K. Bjørlykke
number of minor rivers in Texas. Here sediment transport takes place along the coast from east to west.
Because the active part of the Mississippi delta lies
as far east as it does today, less sediment arrives at the
Texas coast. The fact that this coastline is subsiding at
the same time leads to transgression of the coastline.
This example shows that if the supply of sediment due
to strike feeding cannot match subsidence, the result
will be a transgression.
2.36 The Shore Zone
The shore zone is where land and sea meet, and we can
distinguish between different types:
1. Rocky Beach. The beach is covered with pebbles
and blocks or solid rock representing ancient, resistant bedrock. Much of the coast of Norway is of this
type, but only 2% of the coastline of North America. Rocky beaches form in areas which have been
uplifted tectonically, and where the coast erodes
metamorphic or eruptive rocks.
2. Sand or Gravel Beach. This is the most common
form of beach zone where we have active sedimentation or erosion of older sediments (makes up 33%
of the coastline of North America).
3. Barrier Island. This is a beach which is separated
from the main coastline by a lagoon. Common in
North America (22%), but less common in other
areas.
4. Muddy Coastlines. Beach zones which consist basically of clay are formed where we have sediments
with a very low sand content, and where there is
little wave activity to wash out or enrich any sand
the sediments might contain. We find this in parts
of clay-rich deltas and estuaries and where there is
abundant vegetation along the beach zone which
protects the clay sediments against erosion (e.g.
mangrove forest).
5. Cheniers are isolated sandy beach ridges on coastal
mud flats. They are abundant along the coastline
around major deltas like the Mississippi and the
Amazon. They require low tidal ranges, moderate
Mediterranean
Sea
Port Said
Cairo
0
10
20 km
Scale
B r a n c h )
Ni le
(Da nie tta
L a k e
M a n z a la
Alexandria
Distributary channel facies
Coastal barrier - strand plain
Coastal basin
Coastal lowlands (salt marsh-alkali flat)
Delta plain
Shelf and prodelta
L a k e b u ru ll u s
L a k e ld k u
N i l e
(R os et ta br an ch )
L a k e M a ry o f
Fig. 2.38 The Nile delta system is an example of a wave-dominated, destructive delta system. (Fisher et al. 1974)
76
K. Bjørlykke