Terrigenous Sediments



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Module 6: Marine Sediments

Terrigenous Sediments:




Comprised of land-derived materials.

Settling rates of sediment particles.

Deposition on continental margins
aided by turbidity currents.
What are Today’s Key Concepts

Understanding Ocean Sediments and
Sedimentation Processes:


Transport of terrigenous sediments to the ocean.

Role of turbidity currents as

mechanism for deposition &
redeposition on continental margins.
Oceans & Global Environment
G131 Oceans & Global Environment
Muddy sediments
in canyon

Two Approaches Size or Origin

Origins of constituent materials:


Terrigenous: materials derived from land

Biogenic: sourced from living organisms.

Hydrogenous: chemical precipitate.

Volcanogenic: volcanic materials (e.g. ash.

Cosmogenic: derived from space.
Classifying Marine Sediments
G131 Oceans & Global Environment
Deep sea
cores: mud
with ash
layer
Volcanic
ash layer
Deep sea
cores:
carbonate
oozes
Mn nodule in clay from Pacific

Terrigenous Sediments
G131 Oceans & Global Environment
Land-derived Materials on Ocean Floor

Physically weathered & eroded rock fragments
from land, altered by chemical weathering.

Transported by rivers & water, by wind (dust
storms), and by ice (glacial sediments).
Classification of Marine Sediments by Source of Particles

Relative proportions of
continental margins
within area of the ocean
Continental margin
profile illustrating
origins of both
terrigenous &
biogenic
components of
marine sediments
via a combination of
settling from
surface waters and
bottom transport.
Continental
Margin
G131 Oceans & Global Environment
Vertical scale exaggerated
Shelf, Slope, Rise
Shelf & Deep Sea
thin layer of
sediment
thick layer
of sediment

Terrigenous Sediments
G131 Oceans & Global Environment
Settling Rates for Particles

Larger particles settle (sink) faster.

Smaller particles take longer to settle and can
therefore be transported further from their
source (e.g. dust or river inputs).
Particle
Sizes
and
Settling
Rates

Turbidites & Deep-Sea Fans
Continental Margin Sediments
G131 Oceans & Global Environment
Turbidity currents
can transport
coarse sands and
gravel down to the
continental rise via
submarine canyons
Deposits formed by
turbidity currents
include graded beds
where pelagic muds
are scoured and
overlain by sands
and gravel with
larger particles at
the base (graded
beds).

Continental Shelf
Shelf Sediments


Land-derived clastic sediments
deposited on continental shelves.


Shelf sediments are redistributed downslope by
turbidity currents to produce graded beds with
finer muds traveling further.
Graded
beds
Turbidite
deposition
Deposition in
submarine fans
G131 Oceans & Global Environment
Graded beds

Sediment Accumulation Rates
G131 Oceans & Global Environment
Rates of
sediment
accumulation
are a function
of the supply
of material
to the ocean.
Hence, they
tend to be
higher in
regions that
receive large
fluxes of
terrigenous
materials
and lower in
regions that
are remote
from land.
Rates range from < 1 cm/ky
to > 5cm/ky

Distribution of Carbonates
G131 Oceans & Global Environment
Coastal Carbonates & Reefs


Favored by low influx of terrigenous
sediment and by warm water.


Predominately low latitude deposits formed
in shallow, warm waters.
Tropical & subtropical settings
Carbonate
& corals
Occur in regions without
major terrigenous inputs

Distribution of Ocean Sediments
G131 Oceans & Global Environment
Surface
sediment
types

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