Terrigenous Sediments

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6. Terrigenous Sediments

Understanding Ocean Sediments and Sedimentation Processes: •Transport of terrigenous sediments to the ocean. •Role of turbidity currents as
Volcanogenic: volcanic materials (e.g. ash. •Cosmogenic: derived from space. Classifying Marine Sediments G131 Oceans Global Environment Deep sea
Mn nodule in clay from Pacific Terrigenous Sediments G131 Oceans Global Environment
Transported by rivers water, by wind (dust storms), and by ice (glacial sediments). Classification of Marine Sediments by Source of Particles
Continental Shelf Shelf Sediments •Land-derived clastic sediments deposited on continental shelves.
Distribution of Carbonates G131 Oceans Global Environment Coastal Carbonates Reefs •Favored by low influx of terrigenous
corals Occur in regions without major terrigenous inputs Distribution of Ocean Sediments

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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