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Sediments
What to Watch for?
You will see the true face of the ocean floor
Covered by sediments, gravel, silt and mud
Sediment particles from land, from biological activity, and
even from space
Sediments can help us define what occurred in recent history
in the ocean basin
Sediment thickest at continental margins
Thinnest over active oceanic ridges
Sedimentary “memory” of ocean basin is short
Think about
Movement, transport, how did the sediment arrive, where did it
come from, and how can we tell the story of the ocean basin
Think about daily contact with marine sediment
Building materials, pool filters, toothpaste, oil, natural gas, paint
Sediment
Particles of
organic or
inorganic
matter that
accumulates in
a loose,
unconsolidated
form.
Major Sediment Input to the Oceans
Source
Estimated Amount (109 tons/yr)
Rivers
18.3
Glaciers and ice sheets
2.0
Wind blown dust
0.6
Coastal erosion
0.25
Volcanic debris
0.15
Groundwater
<0.48
What do sediments look like?
Depends where you are
Atlantic ridge

Sponges and corals may be growing over the dusting of sediment
Smooth ocean floor

Brittle stars feed off surface bacteria and fallen particles of organic
sediment
May see ripples if the bottom has swift currents
Colors differ

Biological
• Often white or cream colored

Silica deposits
• Often gray

Clays on the ocean floor
• Red due to oxidation
• Chocolate brown
Sediment Classifications
Origin
Size
Gravel - Bigger than 2 mm
 Sand – .062 – 2 mm, Big in Ocean Terms
 Silt – .004 - .062 mm, Gritty on Teeth
 Clay - <.004 mm

• Use Size to Determine the Energy of the Environment
Well sorted sediments

Sediments mixture that contains sediments of one size
Poorly sorted sediments

Sediments mixtures that contains a variety of of sizes
Sediment
Gravel
Type
Boulder
Diameter (mm)
>256
Sand
Cobble
Pebble
Granule
Very coarse
65-256
4-64
2-4
1-2
Coarse
Medium
Fine
Very fine
0.5-1
0.25-0.5
0.123-0.25
0.0625-0.125
0.0002-0.004
Mud (silt & clay)
Deep Sea Sedimentation
The Deep sea has two main sources of
sediment:
1. External- terrigenous material transported to oceans
via rivers and wind
2. Internal-biogenic and authigenic from the sea.
Origin of the Particles (Genetic)
Proposed by Sir John Murray and A.F. Renard while studying
sediments during the Challenger expedition
Terrigenous/Lithogenous – terra = Earth, generare = to produce
From Earth
Biogenous – Bio = life, generare = to produce
From life
Zebra Muscles
Diatoms
Hydrogenous/ Authigenic – Hydro = life, generare = to
produce
Precipitates chemically from sea water
Iron Stains in Sink in regular water
Cosmosgenous – cosmos = universe, generare = to produce
Comes from Outer Space
Micro meteorites
Origin Classification
•Terrigenous: Sands and mud produced by
weathering and erosion of rocks on land.
•Biogenic: CaCO3 (calcium carbonate) and SiO2
(silica) muds and oozes composed of hard parts of
organisms.
•Authigenic: formed by precipitation of minerals
in seawater (Manganese (Mn) and Phosphorus (P)
nodules).
•Volcanogenic: ejected from volcanoes (ash).
•Cosmogenous: pieces of meteorites that survive
trip thru atmosphere.
Terrigenous Particles
Coming from islands or nearby continents
Most abundant = Granite
Sources of quartz and clay in the oceans
Earth’s crust is made of minerals
Inorganic crystalline materials that have a specific chemical
composition
Both particles are small enough that they get
transported to deep ocean floor
Transportation?? How did they get there what was the
Transport Agent…
Rivers – Clay  Sand


Mississippi River Delta: Birds Foot
Trapped Near the Continents
How sediments reach deep ocean
Turbidity Currents
Density and Gravity pull particles down Slope
Causes flatness of the abyssal plains


Resistant sandstone - rubble
Turbidity current deposit rubble
Terrigenous Particles
Wind (Eolian)



Covers Long Distances
Small Grain Sizes
Slow Accumulation
Africa's West
Coast:
Sediments that
wind transports
from the Sahara
Desert
Terrigenous Particles
Transportation
Glaciers


Deposits of sediment only happens when glaciers reach
sea level
Iceberg Rafting
Rivers and streams
Eloation
Coccolithophorid
Biogenous Particles
2nd Most abundant source for sediments
Skeletal Components
Sediment Rich in skeletal material “ooze”

Sample must contain more than 30% biogenic material
Two Major Players


CaCO3 Calcium Carbonate: Plants
Foraminifera: Animals
To make an “ooze”


Production ~ Same everywhere
Preservation ~ More soluble at high pressure and low temperature
• As it sinks carbonate needs shallower waters ~ 3500 – 4500 m starts
to dissolve
• When carbonate no longer can be preserved = CCD carbonate
compensation depth

Little Dilution – Rapid input of Something else
• Get away from terrigenous areas
Foraminifera
Foraminifera (zooplankton with CaCO3 shell)
White Cliffs of Dover
Biogenous Particles
Silica
Opal – SiO2 . n H2O

Zooplankton
• Diatoms – Plants
Radiolarians
Zooplankton
To make a Siliceous “ooze”
 Production ~ High Productivity Zones they Do Well
 Preservation ~ Entire Ocean is Under saturated with Silica

• Once animal dies it starts to be dissolved
• Preservation takes place with over whelming the system
– Make a lot so a Few can Survive
– Getting to the sediment is the key
– Micro environment once diatom reaches sediment won’t dissolve
because others already have been and water is saturated with
silica
Diatoms (phytoplankton with SiO2 shell)
Cleaning agents and toothpaste often
contain diatoms because of their sharp
surfaces
Biogenous Sediments
Soft Tissue
Gas Hydrates




Near continental Margins
A lot of methane stored in sediments
Might be a useful source of fuel
Possible Problems
• Limited Stability Range
• Methane is much greater green house gas = AGGRESSIVE
– Large Gaseous Emissions!
Hydrogenous/Authigenic Sediments
Formed by chemical or biochemical reactions on ocean
floor/ formed in the place they now occupy
Nodules of ferromanganese (Fe and Mn) or phosphorite
(P).
Mn found deep sea beds
P found continental margins
Concentric layers of metal oxides accrete on particles
over millions of years (1-4 mm per 106 y).
Contain economically important metals Cu, Zn, Co and
Pb. (but too expensive to harvest).
Origin uncertain (biological?)
Ferromanganese nodules
Floor of South Pacific Ocean.
Nodule size 1-5 cm diameter
Ferromanganese nodules
Cross-section
Hydrogenous
Pebble like
Manganese Nodules
mm per million years, they grow slow
Evaporites – Hydrogenous deposit, precipitates out as
water evaporates
Salts: Evaporates from isolated arms of the ocean

Sea salts
• Red sea
• Persian Gulf

Gypsum
Oolite sands – Calcium carbonate precipitates from shell
fragments, white and rounded

Abundant in many warm, shallow waters
• Bahamas
Deep Sea Sedimentation Process
Distribution of Sea Sediments
Neritic sediments: consist of primary terrigenous
material
Found normally along continental shelf's
Distribution of Deep Sea Sediments
Pelagic sedimentation:
Sediments of the slope,
rise, and deep-ocean that
originate in the ocean
Pelagic:

Inorganic red or brown clays
and silt
• Fine-grained (0.0002 –
0.0004 mm)
• Dominate below waters
with little planktonic
production.
Deep Sea Sedimentation
–Pelagic:
•Oozes
–Deep ocean sediment that has at least 30% of debris from planktonic organisms
–Named after the dominate remnant organism
–Calcareous oozes (CaCO3)
»Shells of foraminifera & pteropods (zooplankton) and coccolithophorids
(phytoplankton).
»Accumulate on seafloor above CCD.
»Forms hard limestone under pressure
–Siliceous oozes (SiO2)
»Shells of radiolaria (zooplankton) and diatoms (phytoplankton).
»Accumulate on seafloor below CCD.
»Accumulate below regions of high diatom production (equator, poles,
upwelling areas)
Deep Sea Sedimentation Distribution
TYPE
COMPOSITION
ATLANTIC
(%)
PACIFIC (%) INDIAN (%)
GLOBAL
(%)
Foram. ooze
Carbonate
65
36
54
47
Pteropod ooze
Carbonate
2
0.1
-
0.5
Diatom ooze
Silica
7
10
20
12
Radiolarian
ooze
Silica
-
5
0.5
3
Red clay
Aluminum
silicate
26
49
25
38
Atlantic Basin
Sediments as thick as 1 km (3,300 feet)
Small area
Great numbers of rivers spilling sediments into
ocean
The Atlantic basin contains a “twolayer-cake” stratigraphy–a thick basal
layer of carbonate ooze overlain by a
layer of mud.
Pacific Basin
Less than .5 km in thickness
Large area
Pacific has many trenches that the sediment
gets trapped
Pacific plate moves across latitudes…
The Pacific
basin contains a
“five-layer-cake”
stratigraphy,
because unlike
the Atlantic its
sea floor as it
spreads crosses
the equator
where the CCD
is lowered to the
ocean bottom.
Continental Margins
Rivers and Erosion allow for a lot of the terrigenous
sediment transported to the margins
Orderly sorting of particles from finest to large grains
Large grains stay near shore
Small grains get carried into the deep ocean
Biogenous Sediments also accumulate in this region
Productivity of near shore waters is normally high
Some sediments are lithified due to the pressure of
overlying sediments.
Exceptions
Shelf deposits are subject to erosion as the sea
level fluctuates.
Ice ages

Exposed shelf leads to further erosion
Studying Sediments
Clamshell sampler - Shallow sediment sampler
Piston Corer
Device
capable of
punching
through as
much as 25 m
of sediment
and returning
an intact plug
of material
Scientist Sample Sediments
Coring Preserves deep Straitigraphy, or Layering
Stratigraphy
Analysis of layered
sedimentary deposits in
the ocean (or on land)
Paleo-oceanogrpahyStudy of the Ocean’s
past
Interpret ocean and
climate history from
evidence in deep-sea
sediments

Started in 1930’s
Andrill
JOIDES: Deep-Sea Drilling Program
(DSDP)
1978
Drills into the ocean floor to take core samples
24 a day
50 scientists
65 crew people
Statistics
Economic Importance
Taken from sedimentary deposits of continental
shelves and rises
36% of the world’s crude oil
28% of its natural gas

125 billion dollars
Sand and gravel estimated over 480 million dollars
Chapter 5 Vocabulary
Silt- Sediment particle between 0.004 and 0.062 mm in
diameter
Sand- Sediment particle between 0.062 and 2 mm in
diameter.
Clay- Sediment particle smaller than 0.004 mm in
diameter the smallest sediment size category.
Well-sorted sediments- A sediment in which particles
are of uniform size.
Poorly-sorted sediments- A sediment in which particles
of many sizes are found.
Terrigenous Sediments- Sediment derived form the
land and transported to the ocean by wind and flowing
water
Biogenous Sediments- Sediment of biological origin.
Organisms can deposit calcareous (calcium-containing) or
siliceous (silicon-containing) residue.
Hydrogenous Sediments- A sediment formed directly by
precipitation from seawater; also called authigenic sediment.
Authigenic sediments- Sediment formed directly by
precipitiaon from seawater; also called hydrogenous
sediment.
Cosmogenous sediments- Sediment of extraterrestrial origin.
Microtektites- Translucent oblong particles of glass, a
component of cosmosgenous sediment.
Neritic sediments- Continental shelf sediment consisting
primary of terrigenous material.
Pelagic sediments- Sediments of the slope, rise, and deepocean floor that originate in the ocean.
Turbidites- A terrigenous sediment deposited by a
turbidity current; typically, coarse-grained layers of
nearshore origin interleaved with finer sediments.
Siliceous Ooze- Ooze composed mostly of the hard
remains of silica-containing organisms.
Calcareous Ooze- Ooze composed mostly of the
hard remains of organisms containing calcium
carbonate.
Foraminifera- One of a group of planktonic amoebalike animals with a calcareous shell, which
contributes to biogenous sediment.
Pteropods- A small planktonic mollusk with a
calcareous shell, which contributes to biogenous
sediments.
Radiolarian- One of a group of usually planktonic amoeba-like
animals with a siliceous shell, which contributes to biogenous
sediments.
Diatoms- Earth’s most abundant, successful, and efficient
single celled phytoplankton. Diatoms possess two interlocking
valves made primarily of silica. The valves contribute to
biogenous sediments.
Nodule- Solid mass of hydrogenous sediment, most
commonly manganese or ferromanganese nodules and
phosphorite nodules.
Evaporite- Deposit formed by the evaporation of ocean water.
Oolite sands- Hydrogenous sediment formed when calcium
carbonate precipitates from warmed seawater as pH rises,
forming rounded grains around a shell fragment or other
particle.
Piston Corer- A seabed-sampling device capable of
punching through up to 25 m (80 feet) of sediment and
returning an intact plug of material
Stratigraphy- The branch of geology that deals with the
definitions and description of natural divisions of rocks;
specifically, the analysis of rock strata.
Paleoceanography- The study of the ocean’s past.
Coccolithophores- A very small planktonic alga carrying
discs of calcium carbonate, which contributes to biogenous
sediment.
Calcium Carbonate Compensation Depth (CCD)- The depth
at which rate of accumulation of calcareous sediments
equals the rate of dissolution of these sediments. Below this
depth, sediment contains little or no calcium carbonate.
Clam shell sampler- A sampling device used to
take shallow samples of the ocean bottom.
Minerals- A naturally occurring inorganic
crystalline material with a specific chemical
composition and structure.
Lithification- Conversion of sediment into
sedimentary rock by pressure or by the
introduction of a mineral cement.
Homework with in Chapter 5 - Book
Read Chapter 5 take notes
Make flashcards of vocab terms
Pg. 142 Review Questions – 1, 2, 3
Pg. 142 Critical Thinking Questions – 1, 2