- Slides: 29
Deep Sea Sediments
A. Ocean Zones photic 100 m dysphotic 1. Litttoral Zones 2. Neritic Zones 3. Pelagic Zones 4. Benthic Zones 5. Photic Zones aphotic
B. Terms to know referring to ocean zones: 1/ Neritic- “of the coast”; Coastal; Continental Shelf. 2/ Pelagic- “of the sea”; Marine;
C. Sources of Sediment 1. 2. 3. 4. Terrigenous- “earth produced” Biogenous- “life produced” Hydrogenous- “water produced” Cosmogenous- “universe produced”
D. Terrigenous: “from land”. 1. Desert sand blows off continent to ocean 2. Volcanic eruptions- dust and magma 3. Rivers- sediments transported onto continental shelves Mt. St. Helens
4. Turbidity Currents: Avalanches of muddy ocean waters made heavy by terrigenous sediments. They flow down continental slopes and submarine canyons forming continental rise. Sorted by size of sediments… gravel-sand-silt-clay. https: //www. youtube. com/watch ? v=8 g. YJJjx. Y 8 g 0
E. Pelagic Sediments: Sediments that come from open ocean water, not from land. Form in deep seas far from land. Atlantic: over 3, 000 feet thick Pacific: over 1, 600 feet thick
E. Pelagic Sediments: Oozes: Fine muds with >30% biological materials (pieces of living things). Clays: fine dust size particles containing <30% biological materials. Besides clay, contains pieces of living things (marine snow Ca. CO 3 ), micrometeorites, and volcanic dust.
F. Biogenous: from living things. 1. Mostly calcareous Ca. CO 3 and siliceous Si. O 3 from zooplankton(animal) and phytoplankton(plant) 2. Parrotfish: It crunches coral into white tropical sands… to feed on algae in dead coral. https: //www. youtube. com/watch? v=n. Oa. JW 5 b. Xo. BU
3/ Oozes: Pelagic(marine) sediments containing >30% microorganism shells. 4/ Two Types of Oozes: 1/ calcareous Ca. CO 3 2/ siliceous Si. O 3 3/ Abundant where ample nutrients encourage high biological productivity of plankton (zoo, phyto).
5/Calcareous Oozes: Calcium carbonate or calcite (Ca. CO 3) 1. Coccolithophores (phytoplankton-algae) Chalk- Rock made of coccolith rich sediments. White Cliffs of Dover in England. 2. Foraminifers (zooplankton-protozoa) 3. Dissolve in deepest waters! Below CCD (Ca. CO 3 composition depth)… acidic.
6/ Siliceous Oozes: (Si. O 2) glassy 2. Diatom- phytoplankton 1. radiolarian- zooplankton 4. Diatomaceous earth 3. Concentrated in sediment made up of deepest waters! Do not mostly diatoms. Uses: dissolve below CCD…not filter systems, Ca. CO 3! toothpaste, and paints.
7/ Biogenous ooze turns to rock 1. When biogenous ooze hardens and lithifies, it can form: a. Diatomaceous earth (if composed of diatom-rich ooze) b. Chalk (if composed of coccolith-rich d. White Cliffs of ooze) Dover in southern c. Fossiliferous England limestone
d. White Cliffs of Dover in southern England
8/ Distribution of biogenous ooze 1. Most biogenous ooze found as pelagic deposits at the bottom of the open ocean. 2. Factors affecting the distribution of biogenous ooze: a. Productivity (amount of organisms in surface waters) b. Destruction (dissolving at depth) c. Dilution (mixing with lithogenous clays)
G. Red Clays 1. Red or brown sediment with less than 30% biogenic material. 2. Form in the deepest calmest areas of the ocean. 3. Tiny particles take 100 years to descend. 4. No Ca. CO 3. It dissolves at great depths! Below CCD. 5. It accumulates very slowly 0. 2 cm/1000 years
H. Cosmogenous sediments: tektites 1. Extraterrestrial in origin 2. Two main types: a. Microscopic space dust b. Macroscopic meteor debris 3. Forms an insignificant proportion of ocean sediment
I. Hydrogenous sediment 1. Form when dissolved materials come out of solution as precipitates or evaporates. 2. Precipitation is caused by a change in conditions including: a. Changes in temperature (evaporation) b. Changes in pressure c. Addition of chemically active fluids (like CO 2)
3/ Types of hydrogenous sediment: 1. 2. 3. 4. 5. Manganese nodules Phosphates Carbonates Metal sulfides Evaporite salts
4. Manganese nodules: A treasure chest! 1. 1 st discovered by Challenger expedition (1873) 2. 16 million tons accumulate each year 3. Growth rate: 1 -10 mm every million years
4. Manganese nodules: A treasure chest! 1. Potato to beachball sizegrow from nucleii of bone or teeth. 2. Manganese and iron oxides. Also, Cr, Ni, Cu, Mb, and Zn.
6. Mining has not developed because: 1. Metal prices are not high enough 2. Legal issues 3. Technical issues 4. Environmental issues
The Blake Terrace and Manganese and phosphate pavement. A rich source of metal deposits above abyssal depths due to Gulf Stream Current preventing sediment accumulations.
https: //www. youtube. com/watch? v=byu_X 4 Gcmcc
Map of the World Ocean showing generalized distribution of the principal kinds of sediment on the ocean floor
Summary of Sediment Map: 1. Red Clays occur in the deepest calmest parts of the ocean with low productivity. 2. Siliceous oozes occur in the deep oceans below CCD in areas with high productivity. 3. Calcareous oozes occur in areas of ocean with high productivity and above CCD level like plateaus, seamounts, m-o ridges. 4. Terrigenous sediments occur closer to continents along continental margins. 5. Manganeses nodules occur on abyssal plains and some plateaus (Blake).
Deep Ocean Characteristics 1. 2. 3. 4. 5. 6. 7. 8. 9. Cold Still Stable Dark Essentially no productivity Sparse Life Extremely high pressure Little food Calcium and oxygen ‘starved’