chapter 14: sediments
DESCRIPTION
Chapter 14: Sediments. Oceanography 2014. Vocabulary. Stratigraphy Terrigenous Sediments ( Lithogenous ) Biogenous Sediments Calcareous Ooze Siliceous Ooze Hydrogenous Sediments Evaporites Cosmogenous Sediments Diatomaceous Earth Grain Size Mud Well Sorted Sediment. Root Words. - PowerPoint PPT PresentationTRANSCRIPT
Oceanography 2014
Chapter 14: Sediments
1. Stratigraphy
2. Terrigenous Sediments (Lithogenous)
3. Biogenous Sediments
4. Calcareous Ooze
5. Siliceous Ooze
6. Hydrogenous Sediments
7. Evaporites
8. Cosmogenous Sediments
9. Diatomaceous Earth
10.Grain Size
11.Mud
12.Well Sorted Sediment
Vocabulary
Terra- Hydro-Bio- Cosmo-
Root Words
Sedimentation: the accumulation of sediments
Weathering: process of breaking down rocks to create sediments
Erosion: movement of sediments by wind, gravity, or water
Sedimentation
Sediments are classified by grain size and origin Grain Size: from largest (coarse) to smallest (fine) is gravel, sand, silt, and clay
Mud = silt + clayLoam = sand + silt + clay
Origin: land, organisms, chemicals, volcanoes, and space (see table)
Poorly sorted sediment: sample contains a mixture of sediment sizes.Well sorted sediment: sample contains similar or same sized particles.
Sediment Classification
Origin of SedimentsType Origin Composition Location
Terrigenous From land by rivers, glaciers, & wind
Quartz and feldspar(sand and mud)
Rivers: temperate regions All: continental shelves
Biogenous Organisms, Shells, & skeletons
Carbon based; calcium-type (calcareous ooze) and silicon-type (siliceous ooze)
Tropical continental shelves and deep sea
Hydrogenous Chemicals including biochemicals
Ferromanganese nodules; phosphorites (organic debris from upwelling)
Deep sea deposits; continental shelves
Volcanogenic Volcanic eruptions
Cosmogenic Particles that fall from space
Sediment Classifications
Classification Grain Size ExampleClay <0.004 mm Talc, dusty powderSilt 0.004 – 0.0625 mm Heavy powderSand 0.0625 – 2 mm Sugar crystalsGranule 2 – 4 mm Aquarium gravelPebble 4 – 64 mm Grape-sizedCobble 64 – 256 mm Orange-sizedBoulder 256 mm +++ Brick or larger
Where do sediments come from?RiversGlaciersWavesWindsDissolving pieces of living things (biogenous)Chemical reactions
Terrigenous SedimentsMost abundant sediment
45% of all ocean sediment
Found at continental margins, abyssal plains and polar areas
River deposition: Atlantic Ocean: Amazon River Pacific Ocean: very little river deposition
Wind deposition: Dust blown across deserts Sahara Desert – Atlantic Ocean Gobi Desert – Pacific Ocean
What do you see here?
What do you see here?
Biogenic Sediment Second most abundant
Most common throughout the ocean
Found in deep ocean basins
Depends on biological productivity and rate of decomposition
Hard parts of organism preserved Calcareous Siliceous
Calcareous OozeFormed from the
shells of pteropods, forminifera and coccolithophores
Siliceous OozeDiatoms
Biogenic Sediment: Oozes
Low abundance 1% of all ocean sediment
Formed from dissolved solids precipitating out of seawater Most common: manganese nodules
composed of layers of metals such as manganese, iron, nickel, cobalt, and copper
Hydrogenous Sediment
Cosmogenic SedimentLeast abundant SedimentSources include interplanetary dust,
meteorites, asteroids, and comets
Distribution of Sediments
Displays the relationship between particle size and energy for erosion, transportation and deposition.
Hjulstrom’s Diagram
Continental Shelf, Slope and Rise
Controlled by tides, waves and currents
Main type of sediment found: Terrigenous and Biogenous
How is it getting to these areas? River Deposition (large particles) Currents Moving Sediment(sand and large particles) Waves Moving Sediment(silt and clay)
How fast can it accumulate? Depends on area Ranges from 10 centimeters to 7 meters per year
Important note about the Atlantic coast: much of the sediment is trapped by estuaries and does not reach the ocean.
Sedimentation at Continental Margins
Calcareous biogenic sediments dominate tropical shelves. River-supplied sands and muds dominate temperate shelves. Glacial till and ice-rafted sediments dominate polar shelves.
Shelf Sediment Type by Region
Sedimentation at Deep Ocean BasinsMain type of sediment found: Terrigenous,
Biogenous, and Hydrogenous
Sediments Found: Manganese Nodules (hydrogenous) Turbidites (terrigenous) Clays (terrigenous)
Cover 31% of deep ocean Accumulation: 2 mm/ 1000 years
Oozes (biogenic) Accumulation: 1-6cm/ 1000 year
Tools and Techniques:1. Clam-Shell “Grab” Samplers2. Piston Corers3. Deep-Sea Drilling4. Seismic Profiling
Studying Sediments
Grab samplers take a “bite” out of the sediment covering the bottom.
Corers use a weight to drive a core barrel into a soft bottom.
Economics1/3 of oil and gas reserves are on the continental
marginsSand and Gravel from ocean sources are a $480
million industry
MedicinesMicrobes living in ocean sediment have been used to
make antibioticsIn 2003, a group of bacteria was found within ocean
sediment that could be used to make a medicine to treat cancer
Why are Sediments Important?
Oceanography March 19, 2014
What are sediments? Where do they come from?
Oceanography March 21, 2014Sediment Classification
1. Name two ways sediments can be classified.
2. What does “bio” mean? How does that relate to a type of marine sediment?
Oceanography March 20, 2014Sediment Types
1. What role does weathering and erosion play on the introduction of sediments to the ocean?
2. Speculate on why you think cosmogenic sediments would be the least common.
Oceanography March 28, 2014Sediment Sampling
1. Why would scientists want to collect samples of oceanic sediment?
2. What are two types of information that could be determined from a sample of ocean sediment.
3. Name two ways sediment can be sampled.
Oceanography March 20, 2014Biogenic Sediments
1. What are the two types of biogenic sediment?
2. How do they form?3. Hjulstrom’s Diagram
Oceanography March 20, 2014Sedimentation Factors
What does a Hjulstrom’s Diagram explain?
Oceanography March 20, 2014Continental Sedimentation
What factors control sedimentation at continental margins?