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)

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

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

11. Cosmogenous: Examples Nickel-iron spherules Tektites Silicate chondrules

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

13. 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

14. 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

15. 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!)

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

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