Chapter 14 Sediments Oceanography 2014 Vocabulary 1 Stratigraphy

Chapter 14: Sediments Oceanography 2014

Vocabulary 1. Stratigraphy 7. Evaporites 2. Terrigenous Sediments 8. Cosmogenous Sediments (Lithogenous) 9. Diatomaceous Earth 3. Biogenous Sediments 10. Grain Size 4. Calcareous Ooze 11. Mud 5. Siliceous Ooze 12. Well Sorted Sediment 6. Hydrogenous Sediments

Root Words �Terra�Hydro�Bio�Cosmo-

Sedimentation � Sedimentation: the accumulation of sediments � Weathering: process of breaking down rocks to create sediments � Erosion: movement of sediments by wind, gravity, or water

Sediment Classification Sediments are classified by grain size and origin � Grain Size: from largest (coarse) to smallest (fine) is gravel, sand, silt, and clay Mud = silt + clay Loam = 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.

Origin of Sediments Type Origin Composition Location Terrigenous From land by rivers, glaciers, & wind Quartz and feldspar (sand 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 Example Clay <0. 004 mm Talc, dusty powder Silt 0. 004 – 0. 0625 mm Heavy powder Sand 0. 0625 – 2 mm Sugar crystals Granule 2 – 4 mm Aquarium gravel Pebble 4 – 64 mm Grape-sized Cobble 64 – 256 mm Orange-sized Boulder 256 mm +++ Brick or larger

Where do sediments come from? �Rivers �Glaciers �Waves �Winds �Dissolving pieces of living things (biogenous) �Chemical reactions

Terrigenous Sediments � Most 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?

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

Biogenic Sediment: Oozes �Calcareous Ooze � Formed from the shells of pteropods, forminifera and coccolithophores �Siliceous Ooze � Diatoms

Hydrogenous Sediment � 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

Cosmogenic Sediment � Least abundant Sediment � Sources include interplanetary dust, meteorites, asteroids, and comets

Distribution of Sediments

Hjulstrom’s Diagram Displays the relationship between particle size and energy for erosion, transportation and deposition.

Sedimentation at Continental Margins 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 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.

Shelf Sediment Type by Region � Calcareous biogenic sediments dominate tropical shelves. � River-supplied sands and muds dominate temperate shelves. � Glacial till and ice-rafted sediments dominate polar shelves.

Sedimentation at Deep Ocean Basins �Main 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 -6 cm/ 1000 year

Studying Sediments Tools and Techniques: 1. Clam-Shell “Grab” Samplers 2. Piston Corers 3. Deep-Sea Drilling 4. Seismic Profiling 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.

Why are Sediments Important? Economics � 1/3 of oil and gas reserves are on the continental margins � Sand Gravel from ocean sources are a $480 million industry Medicines � Microbes living in ocean sediment have been used to make antibiotics � In 2003, a group of bacteria was found within ocean sediment that could be used to make a medicine to treat cancer

Oceanography March 19, 2014 What are sediments? Where do they come from?

Oceanography March 21, 2014 Sediment 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, 2014 Sediment 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, 2014 Sediment 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.