Transcript File - COSEE Florida

Fig. CO-4
Marine sediments
Eroded rock particles and
fragments
 Transported to ocean
 Deposit by settling through
water column
 Oceanographers decipher
Earth history through
studying sediments

http://serc.carleton.edu/images/microbelife/topics/proxies/.gif
Classification of marine sediments
 Classified
by origin
 Lithogenous (derived from land)
 Biogenous (derived from organisms)
 Hydrogenous (derived from water)
○ Also known as Authigenic
 Cosmogenous (derived from outer space)
Lithogenous sediments
Eroded rock fragments from land
 Reflect composition of rock from
which derived
 Transported from land by

 Water (e.g., river-transported
sediment)
 Wind
 Ice
 Gravity
Lithogenous sediments
Lithogenous sediments

Most lithogenous sediments at continental
margins
 Coarser sediments closer to shore
 Finer sediments farther from shore
 Mainly mineral quartz (SiO2)
Relationship of finegrained quartz and
prevailing winds
Fig. 4.6b
Distribution of sediments

Neritic
○ Found on continental shelves and shallow
water
○ Generally course grained

Pelagic
○ Found in deep ocean basins
○ Typically fine grained
Distribution of sediments

Neritic
 Shallow water deposits
 Close to land
 Dominantly lithogenous
 Typically deposited quickly
http://disc.gsfc.nasa.gov/oceancolor/images/SeaWiFS_Feb28_sediments_enhanced.jpg
Distribution of sediments

Pelagic
 Deeper water deposits
 Finer-grained sediments
 Deposited slowly
 Sources of fine pelagic lithogenous
sediments:
○ Volcanic ash (volcanic eruptions)
○ Wind-blown dust
○ Fine-grained material transported by
deep ocean currents
Pelagic lithogenous sediments

Abyssal clay (red clay)
 At least 70% of clay-sized
grains from continents
 Transported by winds and
currents
 Oxidized iron – gives reddish
color
 Abundant if other sediments
absent
http://www.ncptt.nps.gov/images/ac/prospection-in-depth2006/album/Whittington/16NA241%20G5%20Closeup%20on%20red%20
clay%20bleeding%20into%20lighetr%20soil.jpg
Biogeneous marine sediments

Hard remains of once-living
organisms
 Shells, bones, teeth
 Macroscopic (large remains)
 Microscopic (small remains)
○ Tiny shells or tests settle
through water column
○ Biogenic ooze (30% or more
tests)
○ Mainly algae and protozoans
http://inst.sfcc.edu/~gmead/ocbasins/CALCCORL.gif
Biogeneous marine sediments

Commonly either calcium
carbonate (CaCO3) or silica
(SiO2 or SiO2·nH2O)

Usually planktonic (freefloating)
○ When the plankton die, they
settle on the bottom
Silica in biogenic sediments

Diatoms (algae)
 Photosynthetic
 Where they are abundant,
thick deposits accumulate
when they die
 Diatomaceous earth – light
white rock

Radiolarians (protozoans)
 heterotrophic

Produces siliceous ooze
Siliceous ooze


Seawater undersaturated with silica so continually
dissolves back into water
Therefore, detectable “siliceous ooze” commonly
associated with high biologic productivity in surface
ocean because once buried, they don’t dissolve easily
Fig. 4.11
Calcium carbonate in biogeneous
sediments

Coccolithophores
(algae)
 Photosynthetic
 Coccoliths (nano-
plankton)
 Accumulation of dead
ones results in
 Rock chalk
Fig. 4.8a
Calcium carbonate in biogeneous sediments

Foraminifera
(protozoans)
 Heterotrophic
 Calcareous ooze
Fig. 4.8c
http://serc.carleton.edu/images/microbelife/topics/proxies/foraminefera.jpg
Carbonate deposits (CO3)

Limestone
 Lithified carbonate
sediments

White Cliffs of Dover, England is
hardened coccolithophore ooze


CaCO3
Stromatolites
 Warm, shallow-
ocean, high salinity
 Cyanobacteria
Fig. 4.10a
Hydrogenous marine sediments

Minerals precipitate directly from seawater
 Manganese nodules
 Phosphates
 Carbonates
 Metal sulfides
Deep sea ferromanganese nodules on the
floor of the South Pacific Ocean (individual
nodules are 5-10 cm diameter).
Small proportion of marine sediments
 Distributed in diverse environments

http://www2.ocean.washington.edu/oc540/lec01-16/99.540.1.2.jpg
Iron-manganese nodules
Fist-sized lumps of manganese, iron, and
other metals
 Very slow accumulation rates
 Why are they on surface sea floor?

 Very puzzling to ocean chemists
Fig. 4.15a
Hydrogenous marine sediments

Phosphates
 Phosphorus-bearing apatite sedimentary rock
 Occur beneath areas in surface ocean of very high
biological productivity  phosphates released into
interstitial water by decomposition
 Economically useful: fertilizer
A phosphate mine in Hardee County in central
Florida. Seventy-five percent of the phosphate
used in the United States comes from the region.
http://www.nytimes.com/2007/08/04/us/04phosphates.html?_r=1&oref=slogin
http://www.outreach.canterbury.ac.nz/resources/geology/glossary/calcite.jpg
Hydrogenous marine sediments
Aragonite
 Carbonates
(CaCO3)
 Aragonite and calcite
○ Calcite found in limestones, marbles,
chalks
○ Used in antacids, toothpaste
○ Aragonite (marine shells) is less stable
and reverts to calcite crystalline form
over time
Calcite
○ Used in cement, fertilizer
 Oolites
○ Small, round calcite spheres found in
shallow, tropical waters with high
carbonate concentrations
○ Precipitates around ‘nucleus’
○ Small, used in aquariums
Oolitic sand
http://www.advancedaquarist.com/2005/2/short
_album/GreatSaltLakeSand.jpg/variant/medium
Hydrogenous marine sediments
 Metal sulfides
 Contain iron,
nickel, copper,
zinc, silver, and
other metals
 Associated with
hydrothermal
vents
http://scienceblogs.com/deepseanews/2008/03/deep_oceans_and_deep_space.php
http://www.geocities.com/rhorii/PhotoGallery/BayfrontParkSaltPond.jpg
Hydrogenous marine sediments
 Evaporites
 Minerals that form
when seawater
evaporates
Salt Pond, Menlo Park's Bayfront
Park, San Francisco
 Restricted open
ocean circulation
 High evaporation
rates
 Halite (common table
salt) and gypsum
http://www.pitt.edu/~cejones/GeoImages/1Minerals/2SedimentaryMineral
z/Gypsum_Halite/GypsumSelenite.JPG
Gypsum
http://upload.wikimedia.org/wikipedia/commons/thumb/5/5c/Two_tektites.JPG/800px-Two_tektites.JPG
Cosmogenous marine sediments
Macroscopic meteor
debris
 Microscopic iron-nickel
and silicate spherules

Tektites
 Tektites
 Space dust

Overall, insignificant
proportion of marine
sediments
Space dust
Mixtures of marine sediments

Usually mixture of different
sediment types
 For example, biogenic oozes
can contain up to 70% nonbiogenic components

Typically one sediment type
dominates in different areas
of sea floor
http://lh5.ggpht.com/_xdSF9NzTieY/SGE4kkTxFEI/AAAA
AAAACsk/FPHuZspT7SM/Zou+zou's+mud+2.JPG
How sea floor sediments represent
surface ocean conditions
Microscopic tests sink slowly
from surface ocean to sea
floor (10-50 years)
 Tests could be moved
horizontally
 Most biogenous tests clump
together in fecal pellets

Sediment trap sample shows
cylindrical fecal pellets and
other aggregates, planktonic
tests (round white objects),
transparent snail-like
pteropod shells, radiolarians,
and diatoms.
 Fecal pellets large enough to sink
quickly (10-15 days)
http://www.whoi.edu/cms/images/oceanus/2005/7/v40n2-honjo1en_4948_12102.jpg
Marine sediments often represent ocean
surface conditions  preserves record of past









Temperature
Nutrient supply
Abundance of marine life
Atmospheric winds
Ocean current patterns
Volcanic eruptions
Major extinction events
Changes in climate
Movement of tectonic plates
Retrieving sediments
 Dredge
 Gravity
corer
 Rotary drilling
 Deep
Sea Drilling
Program
 Ocean Drilling
Program
 Integrated Ocean
Drilling Program
http://www.usgcrp.gov/usgcrp/images/ocp2007/gallery-large/thumbnails/OCP07_Fig-10.jpg
Retrieving sediments
 Studies reveal support for:
 plate tectonics
 drying of the Mediterranean Sea,
 global climate change
Integrated Ocean Drilling Platform.
The dedicated JOIDES Resolution
scientific drilling vessel used for
recovering sequences of sediment and
rock cores from global ocean basins.
Credit: D. Anderson, NOAA/National
Geophysical Data Center.
http://www.usgcrp.gov/usgcrp/images/ocp2007/gallery-large/thumbnails/OCP07_Fig-10.jpg
Resources from marine sediments

Energy resources
 Petroleum
○ Mainly from continental shelves
 Gas hydrates
Sand and gravel (including tin,
gold, and so on)
 Evaporative salts
 Phosphorite
 Manganese nodules and crusts

Ultra-Deep Oil Drilling,
capable of drilling in
10,000 feet of water and
penetrating 30,000 feet
through earth’s crust.
http://joejaworski.files.wordpress.com/2007/09/oil_plat.jpg
Salt deposits
Fig. 4.26
Manganese nodules



Used to obtain
minerals
However, there is
big political issue of
who has rights in
international waters
Used in magnets,
fiber optics,
television displays
Fig. 4.27
Other reasons to study
sediments

Contaminants in water column will
sometimes settle in the sediment
○ Conditions that effect toxicity of sediments
- Sediment type
- Sediment texture (in fine sediment, there is more
surface area for toxins to adhere, increasing
toxicity)
- Dredging and other human activity
○ Sediment Toxicity in Indian River Lagoon
 http://www.teamorca.org/cfiles/fast.cfm
Fig. 4E
Misconceptions
Carbon is only produced by trees.
 The bioshpere has never caused major
changes in the other spheres that
make up the Earth system, such as
the rocks and air.
 Few products we use everyday have
anything to do with taking rocks and
minerals from the ground.
 We will never run out of natural
resources such as coal, oil, and other
minerals.

Ocean Literacy Principles


1g. - The ocean is connected to major lakes, watersheds and waterways because all major
watersheds on Earth drain to the ocean. Rivers and streams transport nutrients, salts, sediments and
pollutants from watersheds to estuaries and to the ocean.
1h. - Although the ocean is large, it is finite and resources are limited.
Sunshine State Standards

SC.6.E.6.1
Describe and give examples of ways in which Earth's surface is built up and torn
down by physical and chemical weathering, erosion, and deposition.

SC.912.E.6.5
Describe the geologic development of the present day oceans and identify
commonly found features.