1. Marine Sediments

2. When I think of the floor of the deep sea, the single, overwhelming fact that possesses my imagination is the accumulation of sediments. I see always the steady, unremitting downward drift of material from above, flake upon flake, layer upon layer
….For the sediments are the material of the most stupendous snowfall the Earth has ever seen

3. Marine sediments - origin
Eroded rock particles and fragments
Biological
Chemical
Deposit by settling through water column
Oceanographers decipher Earth history
through studying sediments and sedimentary rock

4. Origen of sediments
Lithogenous
Biogenous
Hydrogenous
Cosmogenous

5. lithogenous Rock fragments Reflects the composition of the parent rock
Continental margins
Mostly silicate
Coarser closer to shore
Finer farther away

6. How do they get there?
From where?
How is this related to the watershed?

7. Biogeneous sediment Hard remains of once-living organisms
Shells, bones, teeth
Macroscopic (large remains)
Microscopic (small remains)
Tiny shells or tests settle through
water column

8. Mainly algae and protozoans
Ca CO3, silica
From diatoms, radiolarians,

9. Siliceous ooze Seawater undersaturated with silica
Siliceous ooze commonly associated with high biologic productivity in surface ocean
When the ooze lithifies it turns into ‘diatomaceous earth’

10. To get Ca ooze deposits you need shallow depth
To get Si ooze deposits you need really high production

11. Hydrogenous marine sediments
Minerals precipitate directly from
seawater. It used to be dissolved
Manganese nodules
Phosphates
Carbonates
Metal sulfides
Small proportion

12. Distributed all around in diverse communities

13. Iron-manganese nodules
Deep ocean floor
Fist-sized lumps of manganese, iron, and other
metals
Very slow accumulation rates

14. Metal sulfides
Contain iron, nickel, copper, zinc, silver,
and other metals
Associated with hydrothermal vents
Evaporites
Minerals that form when seawater
evaporates…salts (not just NaCl)
Restricted open ocean circulation
High evaporation rates
Halite (common table salt) and gypsum (drywall)

15. Cosmogenous marine sediments
Macroscopic meteor debris
Microscopic iron-nickel and silicate spherules
Tektites
Space dust
Insignificant proportion

16. Mixtures of marine sediments
Usually mixture of different sediment types
For example, biogenic oozes can contain
up to 70% non-biogenic components

17. Typically one sediment dominates a certain area

18. Distribution of neritic and pelagic marine sediments
Neritic sediments cover about ¼ of sea floor and are
composed of lithogenouse sediment almost exclusively
Pelagic sediments cover about ¾ and can be made up of
lithogenous (clays), biogenous, and hydrogenous

19. Distribution controlled by Proximity to sources of lithogenous sediments
Productivity of microscopic marine organisms
Depth of water
Sea floor features

20. How do sea floor sediments ?
represent surface ocean conditions
Microscopic tests sink slowly from surface
ocean to sea floor (10-50 years)
Tests could be moved horizontally yet
sediment deposits do reflect surface water
conditions
Most biogenous tests clump together in fecal pellets
Fecal pellets large enough to sink quickly (1

21. Marine sediments often represent ocean surface conditions
Temperature
Nutrient supply
Abundance of marine life
Atmospheric winds
Ocean current patterns
Volcanic eruptions
Major extinction events (K-T boundary)
Changes in climate
Movement of tectonic plates