Chapter 4
Marine Sedimentation
© 2006 Jones and Bartlett Publishers
Classification of marine sediments can be
based upon size or origin
• Size classification divides
sediment by grain size into
gravel, sand, silt and clay.
– Mud is a mixture of silt and
clay.
• Origin classification divides
sediment into five categories:
–
–
–
–
–
terrigenous sediments
biogenous sediments
hydrogenous sediments
volcanogous sediments
cosmogenous sediments
Figure B4-3 Sediment Cores
4-1 Sediment in the Sea
• Factors that control sedimentation include:
– particle size
– the turbulence of the depositional environment
• Terrigenous sediments strongly reflect their source.
– They are transported to the sea by wind, rivers and glaciers.
• Rate of erosion is important in determining nature of
sediments.
• Average grain size reflects the energy of the depositional
environment.
4-1 Sediment in the Sea
• Hjulström’s Diagram graphs the relationship
between particle size and energy for
– erosion
– transportation
– deposition
Figure 4-1 Hjulström’s Diagram
4-1 Sediment in the Sea
Review
• Based upon water depth, the ocean
environment can be divided into:
– the shelf
• shallow and near a terrigenous source
– the deep ocean basin
• deep and far from a terrigenous source
4-2 Sedimentation in the Ocean
• Shelf sedimentation is strongly controlled by:
– Tides
– Waves
– Currents
• Their influence decreases with water depth.
• Shoreline turbulence prevents small particles
from settling in the shallow water.
• Particle size decreases seaward for recent
sediments.
4-2 Sedimentation in the Ocean
Shelf Sedimentation
Figure 4-2a Model Prediction of Shelf Sediments
4-2 Sedimentation in the Ocean
Sea Level Fluctuation and Coastlines
Past fluctuations of sea level have stranded coarse (relict)
sediment across the shelf.
– This includes most areas where only fine sediments are
deposited today.
Figure 4-2 Shelf Sedimentation
Shelf Sedimentation
Figure 4-3b Relict Sediment
4-2 Sedimentation in the Ocean
• Worldwide distribution of recent shelf sediments
by composition is strongly related to latitude and
climate.
• Calcareous biogenous sediments dominate tropical
shelves.
• River-supplied sands and muds dominate
temperate shelves.
• Glacial till and ice-rafted sediments dominate
polar shelves.
4-2 Sedimentation in the Ocean
Shelf Sedimentation Model
Figure 4-4a Shelf Sedimentation Model
4-2 Sedimentation in the Ocean
Distribution of Shelf Deposits
Figure 4-4b Relative Amounts of Shelf Sediments
4-2 Sedimentation in the Ocean
• Geologic controls of continental shelf sedimentation
must be considered in terms of a time frame.
• For a time frame up to:
– 1000 years, waves, currents and tides control
sedimentation.
– 1,000,000 years, sea level lowered by glaciation controls
sedimentation and cause rivers to deposit their sediments at
the shelf edge and onto the upper continental slope.
– 100,000,000 years, plate tectonics determines the type of
margin that develops and controls sedimentation.
4-2 Sedimentation in the Ocean
Paleogeography of North America
Figure 4-5b Pangaea 100 MYBP
Figure 4-5a North American Paleogeography 100 MYBP
4-2 Sedimentation in the Ocean
Figure 4-5c Western North American
Tectonic Margin (Active Margin)
Figure 4-5d Eastern North
American Nontectonic
Margin (Passive Margin)
4-2 Sedimentation in the Ocean
Development of a Passive Atlantic-type Margin
Figure 4-6a Initial Rifting (Triassic Period: 200 MYBP)
Figure 4-6b Jurassic Margin (150 MYBP)
4-2 Sedimentation in the Ocean
Figure 4-6c Present-Day Margin Southeast of Cape Cod
4-2 Sedimentation in the Ocean
Subduction Tectonics and Sedimentation
Figure 4-7a Volcanic Arc-Trench System
4-2 Sedimentation in the Ocean
Figure 4-7b Accretionary Prism
4-2 Sedimentation in the Ocean
If influx of terrigenous sediment is low and the
water is warm, carbonate sediments and reefs
will dominate.
Figure 4-8 Distribution of Carbonate Shelves
4-2 Sedimentation in the Ocean
• Deep-sea Sedimentation has two main
sources of sediment:
– External – terrigenous material from the land
– Internal – biogenous and hydrogenous from
the sea.
4-2 Sedimentation in the Ocean
Deep-Sea Sedimentation
Figure 4-9a Sedimentation in the Deep Sea
4-2 Sedimentation in the Ocean
Figure 4-9b River Input of Silt to Oceans
4-2 Sedimentation in the Ocean
• Major sedimentary processes in the deep sea include:
– Bulk emplacement
– Debris flows
– Turbidity currents
Figure 4-10a Seismic-Reflection Profile
4-2 Sedimentation in the Ocean
Bulk Emplacement of Sediment to the Deep Sea
Figure 4-10b Turbidity Current
4-2 Sedimentation in the Ocean
Figure 4-10c Turbidite Beds
Figure 4-10c Margin-Sedimentation Model
4-2 Sedimentation in the Ocean
Major pelagic sediments
in the ocean are red clay
and biogenic oozes.
Figure 4-14b Foraminifera
Figure 4-14e Diatoms
4-2 Sedimentation in the Ocean
• Hydrogenous deposits are chemical and biochemical
precipitates that form on the sea floor. They include:
– ferromanganese nodules
– phosphorite
Figure 4-15b Global Distribution of Ferromanganese Nodules
4-2 Sedimentation in the Ocean
• The distribution of sediments in the deep
ocean reflects:
– Latitude
– distance from landmasses
– the calcium carbonate compensation depth
• Glacial marine sediments occur in the high
latitudes.
• Pelagic clays occur far from land and in the
deepest water.
4-2 Sedimentation in the Ocean
The Formation of Glacial-Marine Sediments
Figure 4-12a Ice Rafting
4-2 Sedimentation in the Ocean
The Formation of Glacial-Marine Sediments
Figure 4-12b Deep-Sea Deposits Around Antarctica
4-2 Sedimentation in the Ocean
• Calcareous oozes occur above the calcium carbonate
composition depth.
The depth at which surface production of CaCO3 equals dissolution is called the calcium
carbonate compensation depth (CCD) Figure 8.17 . Above this depth, carbonate oozes can
accumulate, below the CCD only terrigenous sediments, oceanic clays, or siliceous oozes
can accumulate. The calcium carbonate compensation depth beneath the temperate and
tropical Atlantic is approximately 5,000 m deep, while in the Pacific, it is shallower, about
4,200-4,500 m, except beneath the equatorial upwelling zone, where the CCD is about
5,000 m. The CCD in the Indian Ocean is intermediate between the Atlantic and the Pacific.
The CCD is relatively shallow in high latitudes.
4-2 Sedimentation in the Ocean
• The rate of sedimentation depends on the type of sediment
in deep sea.
Figure 4-13 Clays in Deep-Sea Muds
4-2 Sedimentation in the Ocean
Global Deep-Sea Deposits
Figure 4-16a Deep-Sea Sediment Distribution
4-2 Sedimentation in the Ocean
Global Deep-Sea Deposits
Figure 4-16b Sedimentation Rates
4-2 Sedimentation in the Ocean
• Deep-sea stratigraphy refers to the broadscale layering of sediments that cover the
basaltic crust.
• The stratigraphy of the deep sea is strongly
influenced by sea-floor spreading.
4-2 Sedimentation in the Ocean
• The Atlantic basin contains a “two-layer-cake”
stratigraphy – a thick basal layer of carbonate
ooze overlain by a layer of mud.
Figure 4-17 Stratigraphy of the Atlantic Basin
4-2 Sedimentation in the Ocean
• The Pacific basin contains a “four-layer-cake” stratigraphy.
• It crosses the equator where the CCD is lowered to the
ocean bottom.
Figure 4-18a Pacific Ocean
4-2 Sedimentation in the Ocean
Stratigraphy of the Pacific Basin
Figure 4-18b Stratigraphy of the Pacific Basin
4-2 Sedimentation in the Ocean
Figure 4-18c Model to Account for Pacific Stratigraphy
4-2 Sedimentation in the Ocean
• The Mediterranean basin is located where plates are
colliding as Africa moves northward relative to
Europe.
• Anhydrite and stromatolites of Miocene age indicate
that the Mediterranean sea “dried” out between 5 and
25 million years ago.
• Two models have been suggested to account for this
emptying of the Mediterranean Sea of its water.
– The “Uplift” Model
– The “Drying-Out” Model
• After drying out, seawater from the Atlantic Ocean
cascaded down the face of the Gibraltar Sill, refilling
it in about 100 years.
4-2 Sedimentation in the Ocean
The Drying Up of the Mediterranean Sea
The “Uplift” Model
The “Drying-Out” Model