Sedimentology = Study of Marine Sediments

1. Sedimentology = Study of Marine Sediments

2. 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. 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