Marine Sediment Classification: Shape, Size, Formation, and Processes

1. CHAPTER 4 Marine Sediment Classification: Shape, Size, Variation Formation Processes: Lithogenic (rock) Biogenic (organic based) Authogenic/Hydrogenous (precipitated from water) Volcanic Cosmogenic (outer space)

2. Sediment Transport Fluid velocitydetermines thesize of theparticles thatcan be moved

3. Sediment Texture • Grain size sorting • Indication of selectivity of transportation and deposition processes • Textural maturity • Increasing maturity if • Clay content decreases • Sorting increases • Non-quartz minerals decrease • Grains are more rounded (abraded)

4. Sediments • Reflect composition of rock from which derived • Coarser sediments closer to shore • Finer sediments farther from shore • Mainly mineral quartz (SiO2)

5. Terrigenous & Lithogenic sediments (from land) • Rivers • Winds (aeolian) • Glaciers (ice-rafted debris, IRD) • Turbidites • Sea level changes

6. Terrigenous Sediments: • derived from weathering of rocks at or above sea level (e.g., continents, islands) • two distinct chemical compositions • ferromagnesian, or iron-magnesium bearing minerals • non-ferromagnesian minerals – e.g., quartz, feldspar, micas • largest deposits on continental margins (less than 40% reach abyssal plains) • transported by water, wind, gravity, and ice • transported as dissolved and suspended loads in rivers, waves, longshore currents

7. River sediment loads (~109 tons/yr)

8. Sediment Distribution • Neritic • Shallow-water deposits • Close to land • Dominantly lithogenous • Typically deposited quickly • Pelagic • Deeper-water deposits • Finer-grained sediments • Deposited slowly

9. Neritic Lithogenous Sediments • Beach deposits • wave-deposited sand • Continental shelf deposits • Turbidite deposits • Glacial deposits • High latitude continental shelf • Currently forming by ice rafting

10. Pelagic Deposits • Fine-grained material • Accumulates slowly on deep ocean floor • Pelagic lithogenous sediment from • Volcanic ash (volcanic eruptions) • Wind-blown (aeolian) dust • Fine-grained material transported by deep sea currents

11. Dust (LANDSAT image). • Dust comprise much of the fine-grained deposits in remote open-ocean areas (red clays) • primary dust source is deserts in Asia and North Africa

12. Distribution of Sediment on Continental Shelf by Grain Size

13. Continental rise Continental slope Seafloor Features: Continental Margins Submarine canyons (cut into the c. slope) Abyssal plain Continental shelf Abyssal plain

14. Glacial (Ice-rafted debris)

15. boulder to clay size particles also eroded and transported to oceans via glacial ice • glacier termination in circum-polar oceans results in calving and iceberg formation • as ice (or icebergs) melt, entrained material is deposited on the ocean floor • termed 'ice-rafted' debris

16. Biogenic sediments(from living things) Calcareous (CaCO3)Foraminifera -- animalsCoccolithophores -- plants Siliceous (SiO2)Radiolaria -- animalsDiatoms -- plants Forams Diatoms Radiolarian

17. Biogenic Sediment • Two major types: • Macroscopic • Visible to naked eye • Shells, bones, teeth • Microscopic • Tiny shells or tests • Biogenic ooze • Mainly algae and protozoans

18. mm = micron = millionth of a meter!

19. mm = micron = millionth of a meter!

20. mm = micron = millionth of a meter!

21. mm = micron = millionth of a meter!

22. Biogenic Sediments: • composed primarily of marine microfossil remains • median grain size typically less than 0.005 mm (i.e., silt or clay size particles) • characterized as CaCO3 (calcium carbonate) or SiO2 (silica) dominated systems • sediment with biogenic component less than 30% termed calcareous, siliceous clay • calcareous or siliceous 'oozes' if biogenic component greater than 30% 

23. siliceous oozes (primarily diatom oozes) cover ~15% of the ocean floor • distribution mirrors regions of high productivity • common at high latitudes, and zones of upwelling • radiolarian oozes more common in equatorial regions

24. calcareous oozes (foraminifera, coccolithophores) cover ~50% of the ocean floor • level below which no CaCO3 is preserved is the 'carbonate compensation depth‘ (CCD) • This change in dissolution rate is called the lysocline.Below the lysocline, more and more calcium carbonate dissolves, until eventually, there is none left. The lysocline typically occurs at a depth of 3000 to 4000 m

26. Sediment Accumulation

27. Calcium Carbonate Content in Pelagic Oceanic Sediment

29. Rates of Deposition of Marine Sediment

30. Temporal Succession of Pelagic Sediment at Spreading Centers

31. Sediment Succession in Absence of Siliceous Ooze

32. Cosmogenous Marine Sediments • Macroscopic meteor debris • Microscopic iron-nickel and silicate spherules (small globular masses) • Tektites • Space dust • Overall, insignificant proportion of marine sediments

33. Marine Sediment Mixtures Usually mixture of different sediment types Typically one sediment type dominates in different areas of the sea floor.

34. Distribution of Marine Sediments: • sediments thickest along continental margins, thin at mid-ocean ridges  • coastlines • dominated by river-borne and wave reworked terrigenous sediments • shelf and slope characterized by turbidites and authigenic carbonate deposits • glacial deposits and ice-rafted debris common at high latitudes • high input of terrigenous sediments 'dilutes' biogenous components • deep-sea (pelagic) basins • abyssal clays (wind blown deposits) common • lower quantities of biogenic material • distribution of biogenous sediments dependent upon three primary factors • production in surface waters • dissolution in deep waters • dilution by other sediments types