Sedimentology = Study of Marine Sediments

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

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

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

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

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

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)

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

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

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

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

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)

“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

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