Abyssal Plain Sediments Flashcards
Provide some observations
- The thicker sediments are the mouth of large deltas (Mississippi River)
- Thick sediments along coasts (older coast) (Amero Trailing-Edge Coast)
- Along the equator in the Pacific has modestly thicker sediment because of biological activity
- Antarctica (no river) – has a lot of sediment because of biological activity and glaciers eroding the
What is the term called when sediment is from land?
Terrigenous
What is the term called when sediments are from rocks?
Lithogenous
What are the main sediment types of Biogenous?
- Core sample is at least 30% made up of biogenic material
1. Calcareous ooze
2. Siliceous ooze
What are the primary processes of moving terrigenous sediment from land to the marine environment?
- Ice-Rafted Debris
- Rivers
- Wind
- Ash
What is the number one form of moving sediments from land to marine environment?
Melting Ice
What are the main types of terrigenous clays?
- Chlorite
- Illite
- Kaoliniti
- Montmorillonite
Chlorite - Describe the delivery, location found, origin/process.
- By ice, wind, and cold water
- high concentration at high latitudes
- Physical Weathering by melting of ice.
Location Example : Greenland/Antartica
Illite - Describe the delivery, location found, origin/process.
- River and winds
- temperate climates or high altitudes in tropics
- Physical weathering
(think of the sediment types found off the Virginia coast. Red clays - very oxidized)
Kaolinite - Describe the delivery, location found, origin/process.
- Wind
- Common in low latitudes
- Intense chemical weather
Example : Equatorial West Africa
Montmorillonite - Describe the delivery, location found, origin/process.
- Wind
- Common in areas in close proximity to volcanos.
- Chemical weathering
What are sediments called that is made up of 30% or more calcite-based shells?
Calcareous Oozes
What are sediments called that are made up of 30% or more silica-based shells?
Siliceous Oozes (biogenic silica)
What does CCD stand for?
Calcite Compensation Depth
What is the CCD?
The depth at which calcium carbonate (CaCO3) will start to dissolve (ooze sediments)
~3,800 kilometers
Why is the CCD important when considering geological history?
Sediments at larger depths will not have CaCO3 within because they will have dissolved before hitting the seafloor.
This allows you to see how the CCD has changed through time. It also allows you to see how seafloor spreading has played a role in transporting sediment from one place to another.
Explain and draw how the ophiolite complex plays a role in CCD.
Sediments become thicker as the seafloor moves away from the mid-ocean ridge and becomes older and denser.
Increase in-depth as the seafloor moves away from the mid-ocean ridge. Aka starts out in shallow water which is above the CCD. The ridge access tends to concentrate calcareous sediments (oozes). As you move away from the ridge, it gets denser and sinks which then crosses into the CCD. No longer able to preserve the calcareous ooze (common is going to be clay) terrigenous sediments (illite and Kaolinite).
The sedimentation rate before reaching the CCD will accumulate faster than once passed through the CCD. Terrigenous clays do reach the ridges, but they are overwhelmed (30%) by calcareous sediments.
Explain and draw how the rate of seafloor spreading will affect the types of sediments being distributed and where they are found in relation to the ridge axes.
Considered the accumulation rate to be decreasing once through the CCD because it removes all the calcareous sediments out.
Equator = Downwelling Zone (CCD much lower which means get a much higher amount of calcareous ooze)
Can tell the history of where the seafloor has been, history of plate tectonics, and seafloor spreading from the sediments.
The type of red clay would change because you would find chlorite, Illite, Kaolinite at various latitudes.
The transition from Calcareous Ooze to Red Clay is going to happen closer to ridge axes at the slow-spreading ridge (Steep-slope) and much further from a fast-spreading ridge (shallow slope).
What are the main sediments of a hydrogenous sediments
Minerals crystallized directly from seawater
- manganese nodules
- Evaporites (calcium carbonate)
- metal sulfides
- Phosphorites
