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Lecture 2 Marine Sediments And Florida Sediments

Lecture 2 Marine Sediments And Florida Sediments. Marine sediments. Eroded rock particles and fragments Transported to ocean Deposit by settling through water column Oceanographers decipher Earth history through studying sediments.

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Lecture 2 Marine Sediments And Florida Sediments

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  1. Lecture 2Marine SedimentsAnd Florida Sediments

  2. 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

  3. 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)

  4. 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

  5. Distribution of sediments • Neritic • Found on continental shelves and shallow water • Generally course grained • Pelagic • Found in deep ocean basins • Typically fine grained

  6. 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-depth-2006/album/Whittington/16NA241%20G5%20Closeup%20on%20red%20clay%20bleeding%20into%20lighetr%20soil.jpg

  7. 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

  8. Biogeneous marine sediments • Commonly either calcium carbonate (CaCO3)orsilica(SiO2 or SiO2·nH2O) • Usually planktonic (free-floating) • When the plankton die, they settle on the bottom

  9. 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

  10. 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

  11. 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

  12. Hydrogenous marine sediments • Minerals precipitate directly from seawater • Manganese nodules • Phosphates • Carbonates • Metal sulfides • Small proportion of marine sediments • Distributed in diverse environments Deep sea ferromanganese nodules on the floor of the South Pacific Ocean (individual nodules are 5-10 cm diameter). http://www2.ocean.washington.edu/oc540/lec01-16/99.540.1.2.jpg

  13. Cosmogenous marine sediments • Macroscopic meteor debris • Microscopic iron-nickel and silicate spherules • Tektites • Space dust • Overall, insignificant proportion of marine sediments • Tektites • Space dust http://upload.wikimedia.org/wikipedia/commons/thumb/5/5c/Two_tektites.JPG/800px-Two_tektites.JPG

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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

  19. Clay hills of north Florida • Carried from Appalachian mountains

  20. Sand hills • Ancient barrier islands and dunes

  21. 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.

  22. 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.

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