1. Sedimentology = Study of Marine Sediments

2. particles that have accumulated on seafloor
Marine Sediments =
particles that have accumulated on seafloor
Describe different types of sediments by:
source
how transported
chemical make-up
particle size

3. Sorting: measure of the uniformity of grain sizes
Larger particles only travel as far as water has energy to keep them suspended (Think where we see sand)
Smaller can carry further before settling out
Unsorted = Mix of sizes
Well-Sorted = all one size

4. Classification of Sediments by Origin
Four main types:
terrigenous aka lithogenous
biogenous
hydrogenous
cosmogenous

5. 1. Terrigenous Sediments (Lithogenous Sediments)
Source: derived from existing rocks that weather and erode; particles are carried to sea by wind, water, and ice
Location Found: Mostly Continental Margin - near rivers

6. 1. Terrigenous Sediments (Lithogenous Sediments)
Types:
Muds = very fine clay
Glacial = mixed sizes of particles
Icebergs break off, carry stuff with them
Volcanic = usually dust & ash unless close to volcano
Type of rock: quartz (SiO2 –sand), clay, volcanic ash
Amount: 22 billion tons of terrigenous sediment is added to the continental margin each year

7. 2. Biogenous Sediments Source: hard remains of organisms
Shells and skeletons of dead organisms
Diatoms, foraminiferans, radiolarians, and others (TINY)
Most live at surface, get eaten and eliminated, and clumps of skeletons sink
Made of either Calcium Carbonate (CaCO3) or Silica (SiO2)
Location Found: Continental Margin and Pelagic Sea (open ocean)

8. Amount: Form at rate of 1-5 cm/1000 years
Types:
Often fine grained Oozes (contain 30 % microscopic biogenous material)
Shell/coral fragments
Types of rock formed:
Diatomaceous earth (used in toothpaste, filters, medicines, paint, etc.)
Chalk (used for many things including chalkboards)
Limestone (Missouri rock)
Amount: Form at rate of 1-5 cm/1000 years

9. 3. Hydrogenous Sediments
Source: dissolved material in water
Chemical reactions cause dissolved material to precipate
Usually caused by change in temperature or pressure
Location Found: Continental Margin and Pelagic Sea

10. 3. Hydrogenous Sediments
Types (wide variety):
metals
carbonates
phosphates
salts
Amounts: not very much – only when conditions are right
Often found as nodules of iron or manganese
Round blobs about size of baseball
Or slabs
Form around small object such as shark tooth
May be very important economically one day
Minerals for industry, fertilizer

11. 4. Cosmogenous Sediments
Source: from outer space
Space dust
meteors
Location Found: Continental Margin and Pelagic Sea

12. 4. Cosmogenous Sediments
Composition of meteorites:
silicate rock material
iron and nickel
Amount: not very common
Importance: determine large scale cataclysmic changes such as dinosaur extinction (KT boundary - layer of Iridium)

13. “Missing” Sediments
When drilling of seafloor began, scientists didn’t find as much as they expected.
Why?
The older sediments have been subducted back into the mantle

14. Why Study Sediments? Sediments Studies Reveal Earth’s History
Examples:
Past climate
Plate motions
Age of seafloor
Fossil evolution and extinction