1 / 17

Sediments! ☺

Sediments! ☺. January 19, 2009. Wentworth Scale of Grain Size. Boulder Cobble Pebble Granule Sand Silt Clay. Benthic Sediments by the Numbers. Cover 75% of seafloor Oozes = >30% biogenous material Siliceous (14% of ocean surface area) Calcareous (48% of ocean surface area)

kyrene
Download Presentation

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. Sediments! ☺ January 19, 2009

  2. Wentworth Scale of Grain Size • Boulder • Cobble • Pebble • Granule • Sand • Silt • Clay

  3. Benthic Sediments by the Numbers • Cover 75% of seafloor • Oozes = >30% biogenous material • Siliceous (14% of ocean surface area) • Calcareous (48% of ocean surface area) • Abyssal clay (38% of ocean surface area)

  4. Siliceous ooze • SiO2 – opal • Comes from diatoms & radiolarians • Found @ deeper depths • Less abundant han calcareous ooze b/c silica dissolves readily in ocean water • Usu. <100 micrometers

  5. Calcareous ooze • CaCO3 • Comes from coccolithophores & foraminiferans • Dissolves under high pressure (@ great depths) & in basic water, so only found in shallower water (<4500m)

  6. Calcium carbonate • Carbonate compensation depth: depth @ which CaCo3 dissolved @ same rate as replenished from above. Affected by CO2 concentrations, pressure, temperature, pH, productivity of calcareous-shelled organisms. • Lysocline: depth @ which rate of CaCO3 dissolution significantly ↑

  7. Types of Sediment • Lithogenous (rocks, volcanoes, continents) • Biogenous (remains of living organisms, usu. plankton) • Cosmogenous (space) • Hydrogenous (precip of ions dissolved in H2O)

  8. Lithogenous: Examples • Volcanic ash • Ferromagnesian minerals (iron, silicate, magnesium compound) • Igneous rocks • Extrusive = fine-grained • Intrusive = coarse-grained

  9. Biogenous: Examples • CaCO3 (foraminiferans, coccolithophores, coral reefs) • Silica (SiO2) (diatoms, radiolarians)

  10. Cosmogenous: Examples • Nickel-iron spherules • Tektites • Silicate chondrules

  11. Hydrogenous: Examples • Manganese nodules (manganese dioxide, iron oxide) • Phosphorite nodules (P2O5) (grow down into sediment) • Calcium carbonate (not from coral)

  12. Sediment Deposits • Turbidites deposited @ edge of continental margin (form continental rise) • Phosphorite mined→phosphate (fertilizer) • Glacial deposits = from continental shelf, many formed during Pleistocene Epoch • Rafting = sediments carried from shore by icebergs & deposited when they melt • Stromatolites = dome-shaped calcareous structures in shallow water that had been secreted in layers by ancient cyanobacteria

  13. Miscellaneous • Fecal pellets = detritus material from plankton; responsible for carrying particles from shallow depths to deep in ocean • Sediment maturity = ↑ as move away from source→more sorting of particles, ↓ clay content, rounding of grains such as sand • Huljstrom’s Diagram: relationship b/w current velocity & erosion/transportation/deposition of different-sized grains

  14. Accretion • Process by which material is added to a tectonic plate or landmass (could be sediment, volcanic arcs, seamounts, etc.) • Plate accretion (in subduction, sediment scraped off subducted plate attaches to top plate; island arcs & seamounts collide w/ continent, add to it.) W. Coast, E. Coast of Australia, New Zealand. • Landmass accretion (addit. of sediment to coastline/riverbank. Alluvium deposits!)

  15. Random Landforms • Seamount: elevation of sea floor 1000m or higher • Guyot: seamount w/ flat top • Seapeak: seamount w/ peak

  16. Random Terms • Bioturbation: disturbance of sediment near water interface by benthic organisms (burrowing worms)

More Related