Chapter 5: Sediments
Based on data from core samples, scientists have determined the age of portions of
the Pacific floor, measured in mega-annums, or millions of years.
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.
Look For the Following Key Ideas in
Chapter 5
• Ocean sediment includes particles from land, biological activity,
chemical processes and space.
• Ocean sediment is thickest over continental margins and
thinnest over active oceanic ridges.
• Sediment deposited on a quiet seafloor can provide a sequential
record of recent events in the water column above. Sediments
are recycled into earth at subduction zones.
• Sediments are an important source of crude oil and natural gas.
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.
Classifying Sediment
Sediment can be classified by particle size. Waves and
currents generally transport smaller particles farther than
larger particles.
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.
Classifying Sediment
Sediment can also be classified according to its source.
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.
Classifying Sediment
The velocities of currents
vs. erosion rates of
sediments. Note how
weaker currents can move
smaller particles of
sediment, while stronger
currents are needed to
erode larger sediment.
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.
Distribution of Sediments
The sediment of
continental shelves is
called neritic
sediment, and
contains mostly
terrigenous material.
Sediments of the
slope, rise, and
deep-ocean floors
are pelagic
sediments, and
contain a greater
proportion of
biogenous
material.
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.
Sediments of Continental Margins
 Sediments can accumulate to great thickness
on continental margins.
 Shelf sediments can be converted into
sedimentary rock in the process of
lithification.
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.
Sediments of Deep-Ocean Basins
How can the sediments of deep-ocean basins be classified?
1) Turbidites – deposits made by turbidity currents.
2) Oozes – deep-ocean sediment containing at least 30%
biogenous material:
i. Siliceous ooze.
ii. Calcareous ooze.
3) Hydrogenous sediments - originate from chemical
reactions that occur in the existing sediment.
4) Evaporites - salts that precipitate as evaporation occurs.
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.
Sediments of Deep-Ocean Basins
2) Ooze is classified by the type of life form from which it is
derived.
i.
Calcareous ooze is formed by organisms, such as
foraminifera, which contain calcium carbonate in their
shells or skeletons.
ii. Siliceous ooze is formed by organisms that contain silica in
their shells. Diatoms are one type of organism whose
remains contribute to siliceous ooze.
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.
Sediments of Deep-Ocean Basins
3) Hydrogenous sediments are usually the result of chemical
reactions. Hydrogenous sediments are often found in the form
of nodules containing manganese and iron oxides.
4) Evaporites are precipitates that form as water evaporates or as
the conditions in the water change
Evaporites include many salts with economic importance.
Evaporites currently form in the Gulf of California, the Red
Sea, and the Persian Gulf.
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.
Distribution Of Sediments
What differences in the type and distribution of sediments do you
note between the Atlantic Ocean and the Pacific Ocean?
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.
Studying Sediments
How do scientists study sediments?
1) Deep-water cameras.
2) Clamshell samplers.
3) Piston Corers.
4) Core libraries.
5) Seismic profilers.
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.
Studying Sediments
One method of studying sediments uses a clamshell sampler. The
sampler can be used to obtain a relatively undisturbed sediment
sample.
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.
Studying Sediments
One method of obtaining core
samples by research vessels
such as the JOIDES
Resolution is by using a
piston corer.
The corer allows a cylinder of
sediment to be taken for
analysis to determine the age
of the material, as well as the
density, strength, molecular
composition and radioactivity
of the sediment.
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.
Studying Sediments
What can scientists learn by studying
sediments?

Historical information

Location of natural resources, especially
crude oil and natural gas
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.
Chapter 5 Summary
Marine sediments are important as historical records and a
site of natural resources. Scientists study marine sediments
using many different methods, including core samples.
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.
{And We have made from Water every living thing. Will they not then believe?}
(Al-Ambiya: 21, Verse: 30)
 Sediment can be classified by particle size.
 Sediment can also be classified according to its source.
 Weaker currents can move smaller particles of sediment, while
stronger currents are needed to erode larger sediment.
 The sediment of continental shelves is called neritic sediment, and
contains mostly terrigenous material.
 Sediments of the slope, rise, and deep-ocean floors are pelagic
sediments, and contain a greater proportion of biogenous
material.
 Sediments of Continental Margins:
Sediments can accumulate to great thickness on continental margins.
Shelf sediments can be converted into sedimentary rock (lithification).
{And We have made from Water every living thing. Will they not then believe?}
(Al-Ambiya: 21, Verse: 30)
 Sediments of deep-ocean basins can be classified.
1)
Turbidites = turbidity currents.
2)
i.
ii.
Oozes.
Siliceous ooze = foraminifera = calcium carbonate.
Calcareous ooze = Diatoms = silica.
3) Hydrogenous sediments = nodules = containing manganese and
iron oxides.
4)
Evaporites = many forms.
 Scientists study sediments by:
1)
2)
3)
4)
5)
Deep-water cameras.
Clamshell samplers.
Piston Corers.
Core libraries.
Seismic profilers.