Marine Sediments
SO1. Students will identify characteristics, physical
features, and boundaries of the oceans.
d. Identify the sources of the main types of marine
sediments and describe how marine sediments are used
in paleoceanography.
Ocean sediment
Various materials settle through the water
column and accumulate on the ocean floor
Layers represent a record of Earth history,
including:
Movement of tectonic plates
Past changes in climate
Ancient ocean circulation patterns
Catastrophic events
Collecting ocean sediment
Specially
designed ships
collect cores by
drilling
Cores allow
scientists to
analyze ocean
sediment
Figure 4B
The 4 main types of sediment
1. Lithogenous = composed of fragments of
pre-existing rock material
2. Biogenous = composed of hard remains of
once-living organisms
3. Hydrogenous = formed when dissolved
materials come out of solution (precipitate)
4. Cosmogenous = derived from outer space
Origin of lithogenous sediment
Forms by:
Weathering =
breakup of exposed
rock
Transportation =
movement of
sediment
Deposition =
settling and
accumulation
Sediment-transporting media
Lithogenous sediment
composition
Most lithogenous
sediment is
composed of
quartz, which is:
Abundant
Chemically stable
Durable
Origin of biogenous sediment
Organisms that produce hard parts die
Material rains down on the ocean floor and
accumulates as:
Macroscopic shells, bones, teeth
Microscopic tests (shells)
If comprised of at least 30% test material, called
biogenous ooze
Biogenous sediment composition
Microscopic biogenous tests are
composed of 2 main chemical compounds:
1.
Silica (SiO2)
Diatoms (algae)
Radiolarians (protist)
2.
Calcium carbonate or calcite (CaCO3)
Coccolithophores (algae)
Foraminiferans—or forams (protist)
Examples of silica-secreting
microscopic organisms
Diatom
Radiolarian
Siliceous ooze
Silica-secreting
organisms
accumulate to form
siliceous ooze
Examples of calcite-secreting
microscopic organisms
Coccolithophores
Foraminiferans
Calcareous ooze
Calcite-secreting
organisms
accumulate to form
calcareous ooze
Biogenous ooze turns to rock
When biogenous
ooze hardens and
lithifies, can form:
Diatomaceous earth
(if composed of
diatom-rich ooze)
Chalk (if composed
of coccolith-rich
ooze)
White Cliffs of Dover
Biogenous ooze as
environmental indicator
Surface water
temperature
Main locations
found
Siliceous ooze
Cool
Calcareous ooze
Warm
Sea floor
beneath cool
surface water in
high latitudes;
upwelling areas
Sea floor
beneath warm
surface water in
low latitudes; not
too deep
Origin of hydrogenous sediment
Hydrogenous sediment forms when
dissolved materials come out of solution
(precipitate)
Precipitation is caused by a change in
conditions including:
Changes in temperature
Changes in pressure
Addition of chemically active fluids
Types of hydrogenous sediment
Manganese nodules
Phosphates
Carbonates
Metal sulfides
Evaporite salts
Mining
manganese
nodules
Evaporite
salts
Cosmogenous sediment
Cosmogenous sediment is
composed of material derived
from outer space
Two main types:
Microscopic space dust
2. Macroscopic meteor debris
1.
Forms an insignificant
proportion of ocean sediment
Microscopic
cosmogenous
spherule
Worldwide distribution of neritic
and pelagic sediment
Figure 4-17