1 / 38

CHAPTER 4: Marine Sediments

CHAPTER 4: Marine Sediments. 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.

lucas-french
Télécharger la présentation

CHAPTER 4: Marine Sediments

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CHAPTER 4: Marine Sediments Fig. CO-4

  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. Lithogenous sediments

  6. Lithogenous sediments • Most lithogenous sediments at continental margins • Coarser sediments closer to shore • Finer sediments farther from shore • Mainly mineral quartz (SiO2)

  7. Relationship of fine-grained quartz and prevailing winds Fig. 4.6b

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

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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

  16. Calcium carbonate in biogeneous sediments • Coccolithophores (algae) • Photosynthetic • Coccoliths(nano-plankton) • Accumulation of dead ones results in • Rock chalk Fig. 4.8a

  17. Calcium carbonate in biogeneous sediments • Foraminifera (protozoans) • Heterotrophic • Calcareous ooze Fig. 4.8c http://serc.carleton.edu/images/microbelife/topics/proxies/foraminefera.jpg

  18. 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

  19. 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

  20. 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

  21. 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

  22. http://www.outreach.canterbury.ac.nz/resources/geology/glossary/calcite.jpghttp://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 • 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 Oolitic sand http://www.advancedaquarist.com/2005/2/short_album/GreatSaltLakeSand.jpg/variant/medium

  23. 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

  24. http://www.geocities.com/rhorii/PhotoGallery/BayfrontParkSaltPond.jpghttp://www.geocities.com/rhorii/PhotoGallery/BayfrontParkSaltPond.jpg Hydrogenous marine sediments • Evaporites • Minerals that form when seawater evaporates • Restricted open ocean circulation • High evaporation rates • Halite (common table salt) and gypsum Salt Pond, Menlo Park's Bayfront Park, San Francisco Gypsum http://www.pitt.edu/~cejones/GeoImages/1Minerals/2SedimentaryMineralz/Gypsum_Halite/GypsumSelenite.JPG

  25. http://upload.wikimedia.org/wikipedia/commons/thumb/5/5c/Two_tektites.JPG/800px-Two_tektites.JPGhttp://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 • Space dust • Overall, insignificant proportion of marine sediments • Tektites • Space dust

  26. Mixtures of marine sediments • Usually mixture of different sediment types • For 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

  27. How sea floor sediments represent surface ocean conditions Sediment trap sample shows cylindrical fecal pellets and other aggregates, planktonic tests (round white objects), transparent snail-like pteropod shells, radiolarians, and diatoms. • 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 • Fecal pellets large enough to sink quickly (10-15 days) http://www.whoi.edu/cms/images/oceanus/2005/7/v40n2-honjo1en_4948_12102.jpg

  28. 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

  29. 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

  30. 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

  31. 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

  32. Salt deposits Fig. 4.26

  33. 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

  34. 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

  35. Fig. 4E

  36. 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.

  37. 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.

  38. 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.

More Related