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

LithogenousLithogenous (derived from land)BiogenousBiogenous (derived from organisms)HydrogenousHydrogenous (derived from water)

○ Also known as AuthigenicCosmogenousCosmogenous (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 marginsCoarser sediments closer to shoreFiner sediments farther from shoreMainly mineral quartz (SiO2)

Relationship of fine-grained 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 NeriticNeritic

Shallow water depositsClose to landDominantly lithogenousTypically deposited quickly

http://disc.gsfc.nasa.gov/oceancolor/images/SeaWiFS_Feb28_sediments_enhanced.jpg

Distribution of sediments PelagicPelagic

Deeper water depositsFiner-grained sedimentsDeposited 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)Abyssal clay (red clay)At least 70% of clay-sized

grains from continents Transported by winds and

currentsOxidized iron – gives reddish

colorAbundant if other sediments

absent

http://www.ncptt.nps.gov/images/ac/prospection-in-depth-2006/album/Whittington/16NA241%20G5%20Closeup%20on%20red%20clay%20bleeding%20into%20lighetr%20soil.jpg

Biogeneous marine sediments Hard remains of once-living Hard remains of once-living

organismsorganismsShells, bones, teethMacroscopic (large

remains)Microscopic (small remains)

○ Tiny shells or tests settle through water column

○ Biogenic ooze (30% or more tests)

○ Mainly algae and protozoanshttp://inst.sfcc.edu/~gmead/ocbasins/CALCCORL.gif

Biogeneous marine sediments

Commonly either calcium calcium carbonate carbonate (CaCO3) or silicasilica (SiO2 or SiO2·nH2O)

Usually planktonicplanktonic (free-floating)

○ When the plankton die, they settle on the bottom

Silica in biogenic sediments DiatomsDiatoms (algae)

PhotosyntheticWhere they are abundant,

thick deposits accumulate when they dieDiatomaceous earth – light

white rock

RadiolariansRadiolarians (protozoans)heterotrophic

Produces siliceous oozesiliceous 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)PhotosyntheticCoccolithsCoccoliths (nano-

plankton)Accumulation of dead

ones results inRock chalk

Fig. 4.8a

Calcium carbonate in biogeneous sediments

ForaminiferaForaminifera (protozoans)HeterotrophicCalcareous ooze

Fig. 4.8c

http://serc.carleton.edu/images/microbelife/topics/proxies/foraminefera.jpg

Carbonate deposits (CO3)

StromatolitesStromatolitesWarm, shallow-

ocean, high salinityCyanobacteria

Fig. 4.10a

Limestone Limestone Lithified carbonate

sediments White Cliffs of Dover,

England is hardened coccolithophore ooze

CaCO3

Hydrogenous marine sediments Minerals precipitate directly from seawater

Manganese nodulesManganese nodulesPhosphatesPhosphatesCarbonatesCarbonatesMetal sulfidesMetal sulfides

Small proportion of marine sediments Distributed in diverse environments

http://www2.ocean.washington.edu/oc540/lec01-16/99.540.1.2.jpg

Deep sea ferromanganese nodules on the floor of the South Pacific Ocean (individual nodules are 5-10 cm diameter).

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

PhosphatesPhosphatesPhosphorus-bearing apatite sedimentary rockOccur beneath areas in surface ocean of very high

biological productivity phosphates released into interstitial water by decomposition

Economically useful: fertilizer

http://www.nytimes.com/2007/08/04/us/04phosphates.html?_r=1&oref=slogin

A phosphate mine in Hardee County in central Florida. Seventy-five percent of the phosphate used in the United States comes from the region.

Hydrogenous marine sediments

Carbonates (CaCOCarbonates (CaCO33))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○ 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

Calcite

Aragonite

http://www.advancedaquarist.com/2005/2/short_album/GreatSaltLakeSand.jpg/

variant/medium

http://www.outreach.canterbury.ac.nz/resources/geology/glossary/calcite.jpg

Oolitic sand

Hydrogenous marine sediments Metal sulfidesMetal 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

Hydrogenous marine sediments EvaporitesEvaporites

Minerals that form when seawater evaporates

Restricted open ocean circulation

High evaporation rates

Halite (common table salt) and gypsum

http://www.geocities.com/rhorii/PhotoGallery/BayfrontParkSaltPond.jpg

Salt Pond, Menlo Park's Bayfront Park, San Francisco

http://www.pitt.edu/~cejones/GeoImages/1Minerals/2SedimentaryMineralz/Gypsum_Halite/GypsumSelenite.JPG

Gypsum

Cosmogenous marine sediments Macroscopic meteor

debris Microscopic iron-nickel

and silicate spherulesTektitesSpace dust

Overall, insignificant proportion of marine sediments

http://upload.wikimedia.org/wikipedia/commons/thumb/5/5c/Two_tektites.JPG/800px-Two_tektites.JPG

Tektites

Space dust

Mixtures of marine sediments Usually mixture of different

sediment typesFor example, biogenic oozes

can contain up to 70% non-biogenic components

Typically one sediment type dominates in different areas of sea floor

http://lh5.ggpht.com/_xdSF9NzTieY/SGE4kkTxFEI/AAAAAAAACsk/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 pelletsFecal pellets large enough to sink

quickly (10-15 days)

http://www.whoi.edu/cms/images/oceanus/2005/7/v40n2-honjo1en_4948_12102.jpg

Sediment trap sample shows cylindrical fecal pellets and other aggregates, planktonic tests (round white objects), transparent snail-like pteropod shells, radiolarians, and diatoms.

Marine sediments often represent ocean surface conditions preserves record of past

TemperatureNutrient supplyAbundance of marine lifeAtmospheric windsOcean current patternsVolcanic eruptionsMajor extinction eventsChanges in climateMovement 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 tectonicsdrying of the Mediterranean Sea, global climate change

http://www.usgcrp.gov/usgcrp/images/ocp2007/gallery-large/thumbnails/OCP07_Fig-10.jpg

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.

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

http://joejaworski.files.wordpress.com/2007/09/oil_plat.jpg

Ultra-Deep Oil Drilling, capable of drilling in 10,000 feet of water and penetrating 30,000 feet through earth’s crust.

Salt depositsSalt 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 Lagoonhttp://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.