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

Distribution of sediments

Neritic○ Found on continental shelves and

shallow water○ Generally course grained

Pelagic○ Found in deep ocean basins○ Typically fine grained

Pelagic lithogenous sediments

Abyssal clay (red clay)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-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 protozoans

http://inst.sfcc.edu/~gmead/ocbasins/CALCCORL.gif

Biogeneous marine sediments

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

Usually planktonicplanktonic (free-floating)

○ When the plankton die, they settle on the bottom

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

Calcareous Ooze

• Destruction of calcium carbonate varies with depth

• At warmer surface, seawater is saturated with calcium carbonate so calcite doesn’t dissolve

• However, as decomposed material sinks further, it reaches cold ocean water

• Colder water holds more dissolved CO2

• CO2 forms carbonic acid and causes calcareous material to dissolve

• High pressure also helps with this• This is where the CCD is reached (Calcite

Compensation Depth) – below this little calcium carbonate survives

Carbonate deposits (CO3)

StromatolitesStromatolitesWarm, shallow-

ocean, high salinity

CyanobacteriaFig. 4.10a

Limestone Limestone Lithified carbonate sediments White Cliffs of Dover, England is

hardened coccolithophore ooze CaCO3

Hydrogenous marine sediments Minerals precipitate directly from

seawaterManganese 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).

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

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

Resources from marine sediments

Energy resourcesPetroleum

○ 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.

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

Florida Sediments

3 characteristics distinguish Florida from regions to the north

○ Marine sediments, limestone and calcium magnesium carbonate, lie in thick layers at or below surface

○ Whole southeastern US coastal plain is deeply layered with clay, silt, sand, and gravel

○ Layer of organic soil lies on or is mixed into surface sediments

- Can be very thick under wetlands

Clay hills of north FloridaCarried from Appalachian mountains

Sand hillsAncient barrier islands and dunes

Misconceptions – What have we learned that make these statements false?

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.