3 Coastal and Shallow Sea Sediments
(Including Carbonates)
3.1 Beach and Shoreface Sediments
3.1.1 Coastal Proeesses: Waves and Wave-Generated
Currents
3.1.2 Beaeh and Shoreface Sands and Their Budget
The Beach-Shoreface Zone
Bed Forms and Sedimentary Structures
High-Energy Shorelines
Shoreline Migration and Vertieal Sediment
Successions
The Sand Budget of the Beach-Shorefaee Zone
3.1.3 Storms and Storm Deposits (Tempestites)
Storm Generation and Storm Action
Characteristies of Tempestites
Bed forms and Facies Patterns
Other Characteristics ofTempestites
Frequency of Storm Events and Tempestites
Proximal-Distal Trends and Tempestite Sequenees
3.1.4 Summary (Beach and Shoreface)
3.1.1 Coastal Processes: Waves and Wave-Generated Currents
Beach processes and, in a broader sense also coastal
and shelf processes, are controlled predominantly by
wind waves, tidal waves, and wave-generated currents. In this Section, wind waves and wind-generated currents of the coastal zone, generating wavedominated shorelines, are briefly discussed.
Detailed descriptions of these processes have been given in
several books and book chapters (e.g. Komar 1976; Carter
1988; Walker and Plint 1992; Carter and Woodroffe 1994;
Reading and Collinson 1996). Tidal effects and other oceanie eurrents will be referred to in Seets. 3.2 and 3.3.
Waves are the result of mechanical energy transfer
from the wind onto the water surface. The large surface of an ocean can absorb much more energy from
the atmosphere than that of a small lake, i.e., areas
with a long "wind-fetch" can create much larger
waves than water bodies of lirnited length parellel to
the wind direction.
Prirnarily, waves do not transport water and therefore do not induce currents. This is a secondary effect taking place in shallow water where "deep-water
waves" are transformed into "shallow-water waves"
and finally dissipate (Fig. 3.1a).
Deep-water waves only affeet a specific layer of the water
mass. The thiekness of this uppermost layer is approximately L/2, where L is the wave length (Fig. 3.1 a). The
depth of L/2 below the water surface is also referred to as
the wave base or the depth up to which wave-induced currents exert a significant influenee on the sea floor. Between
the water surface and the wave base, the water particles
perform eireular (orbital) movements. At the surface, the
diameter ofthese circles is equal to the wave height H, and
the time T, necessary for a water particle to finish one rotation, is the wave period. This is the same period of time
measured at a fixed point from one passing wave erest to
the next one. Below the sea surface the diameter of the
rotating water particles is redueed and their orbital velocity
slows until this movement almost completely ceases at the
wave base.
Although the water affected by deep-water waves
remains more or less in place, the rnigrating waves
transport energy, for example from localized storm
centers to remote coastlines.
As soon as the water depth is less than the wave
base (L/2), the deep-water waves start to be transformed into shallow-water waves. A significant
change of the wave characteristics takes place, if the
water depth is as shallow as one-sixth to one-eighth
of the wave length. Thereafter, wave length and
speed of wave propagation decrease, but their energy
is packed into a smaller area and their height increases (Fig. 3.1 a). Simultaneously, the formerly circular motion of single water particles is transformed
into an elliptic and, near the sea-bed, into a
bidirectional oscillating movement. Approaching the
shoreface and the beach the waves become shorter,
asymmetrical, and their height increases until they
collapse in the breaker and surf zone at a water depth
of approximately 4/3 H (H is the wave height in deep
water).
If a wave front migrates obliquely toward the
co ast, its landward section "touches the bottom" and
is affected by wave-length reduction earlier than the
(Including Carbonates)
3.1 Beach and Shoreface Sediments
3.1.1 Coastal Proeesses: Waves and Wave-Generated
Currents
3.1.2 Beaeh and Shoreface Sands and Their Budget
The Beach-Shoreface Zone
Bed Forms and Sedimentary Structures
High-Energy Shorelines
Shoreline Migration and Vertieal Sediment
Successions
The Sand Budget of the Beach-Shorefaee Zone
3.1.3 Storms and Storm Deposits (Tempestites)
Storm Generation and Storm Action
Characteristies of Tempestites
Bed forms and Facies Patterns
Other Characteristics ofTempestites
Frequency of Storm Events and Tempestites
Proximal-Distal Trends and Tempestite Sequenees
3.1.4 Summary (Beach and Shoreface)
3.1.1 Coastal Processes: Waves and Wave-Generated Currents
Beach processes and, in a broader sense also coastal
and shelf processes, are controlled predominantly by
wind waves, tidal waves, and wave-generated currents. In this Section, wind waves and wind-generated currents of the coastal zone, generating wavedominated shorelines, are briefly discussed.
Detailed descriptions of these processes have been given in
several books and book chapters (e.g. Komar 1976; Carter
1988; Walker and Plint 1992; Carter and Woodroffe 1994;
Reading and Collinson 1996). Tidal effects and other oceanie eurrents will be referred to in Seets. 3.2 and 3.3.
Waves are the result of mechanical energy transfer
from the wind onto the water surface. The large surface of an ocean can absorb much more energy from
the atmosphere than that of a small lake, i.e., areas
with a long "wind-fetch" can create much larger
waves than water bodies of lirnited length parellel to
the wind direction.
Prirnarily, waves do not transport water and therefore do not induce currents. This is a secondary effect taking place in shallow water where "deep-water
waves" are transformed into "shallow-water waves"
and finally dissipate (Fig. 3.1a).
Deep-water waves only affeet a specific layer of the water
mass. The thiekness of this uppermost layer is approximately L/2, where L is the wave length (Fig. 3.1 a). The
depth of L/2 below the water surface is also referred to as
the wave base or the depth up to which wave-induced currents exert a significant influenee on the sea floor. Between
the water surface and the wave base, the water particles
perform eireular (orbital) movements. At the surface, the
diameter ofthese circles is equal to the wave height H, and
the time T, necessary for a water particle to finish one rotation, is the wave period. This is the same period of time
measured at a fixed point from one passing wave erest to
the next one. Below the sea surface the diameter of the
rotating water particles is redueed and their orbital velocity
slows until this movement almost completely ceases at the
wave base.
Although the water affected by deep-water waves
remains more or less in place, the rnigrating waves
transport energy, for example from localized storm
centers to remote coastlines.
As soon as the water depth is less than the wave
base (L/2), the deep-water waves start to be transformed into shallow-water waves. A significant
change of the wave characteristics takes place, if the
water depth is as shallow as one-sixth to one-eighth
of the wave length. Thereafter, wave length and
speed of wave propagation decrease, but their energy
is packed into a smaller area and their height increases (Fig. 3.1 a). Simultaneously, the formerly circular motion of single water particles is transformed
into an elliptic and, near the sea-bed, into a
bidirectional oscillating movement. Approaching the
shoreface and the beach the waves become shorter,
asymmetrical, and their height increases until they
collapse in the breaker and surf zone at a water depth
of approximately 4/3 H (H is the wave height in deep
water).
If a wave front migrates obliquely toward the
co ast, its landward section "touches the bottom" and
is affected by wave-length reduction earlier than the