Lecture 17: Marine sediment transport and distribution Flashcards
How many land vs sea sediments cover the sea floor?
~1/4 of the seafloor is covered
in neritic sediments.
~3/4 of the seafloor is covered in pelagic sediments.
Know what long shore drift is
yeyeyye
what are terrigenous sediments?
Terrigenous: produced by physical and chemical weathering and
erosion of rocks on land, then transported to the ocean
What are biogenic sediments?
Biogenic: organic precipitation of CaCO3
(calcium carbonate) or SiO2
(silica; “biogenic opal”) hard parts by (dominantly) single-celled marine
organisms
What are Authigenic sediments?
Authigenic: formed by precipitation of minerals in seawater (e.g.
manganese (Mn) and phosphorus (P) nodules).
What are volcanogenic sediments?
Volcanogenic: ejected from volcanoes
What are cosmogenic sediments?
Cosmogenic: extraterrestrial material that survives travel through the
atmosphere and lands in the ocean
What grain size
pattern will turbidity
flow produce?
Coarse grained
sediments are found
at the base of the
deposit, and grain size
gets finer upwards.
Continental shelf sedimentation?
Calcareous biogenic sediments dominate tropical shelves.
River-supplied sands and muds dominate temperate shelves.
Glacial till and ice-rafted debris collectively called glaciomarine sediments dominate polar shelves.
What are nodules?
Precipitate from ions
dissolved in seawater
Grow in place under
favorable geochemical
conditions; some are
biologically mediated
Usually slow-growing;
minor sedimentary
constituent
What controls major lithologies?
Calcareous sediments:
Warm(er) water; low influx of terrigenous
sediment and biogenic opal; accumulation zone above the CCD;
accumulation rate depends on surface productivity
Siliceous sediments: Cool(er) water in polar and upwelling zones
(includes equatorial upwelling); abundant nutrients; low influx of terrigenous sediment; accumulation zone below the CCD; accumulation rate depends on surface productivity
Red clay: mostly derived from continents; accumulates very slowly;
dominant lithology only in regions with minimal dilution from all other
sediment types
Glacial sediments: Delivered by glacial processes; can accumulate very rapidly; sometimes distinguished by large clasts or poor sorting
Terrigenous: Uplift and erosion rates; continental weathering; continental proximity
Carbonate ooze and the CCD?
Warm, shallow ocean holds less dissolved CO2 – it’s saturated with CaCO3 , so carbonate shells are preserved
Cool, deep ocean holds more dissolved CO2 – it’s undersaturated with CaCO3, so carbonate shells dissolve
Lysocline: Depth at which measurable dissolution begins
CCD: Calcite compensation depth
Depth where CaCO3
readily dissolves
Atlantic CCD: ~5000 meters water depth
Pacific CCD: 4200-4500* meters water depth (* ~5000 m at equator)
