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Marine Sedimentation. What is it and where does it come from?. Table 5-1, p. 103. Bottom of the Ocean Floor (Antarctica). How do we know/How do we get it?. Ice samples. River inputs (sedimentation). Atmospheric Inputs. Dust input.
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Marine Sedimentation What is it and where does it come from?
Based upon water depth, the ocean environment can be divided into: • the shelf • shallow and near a terrigenous source • the deep ocean basin • deep and far from a terrigenous source
Shelf sedimentation is strongly controlled by: • Tides • Waves • Currents • Their influence decreases with water depth. • Shoreline turbulence prevents small particles from settling in the shallow water. • Particle size decreases seaward for recent sediments.
Geologic controls of continental shelf sedimentation must be considered in terms of a time frame. • For a time frame up to: • 1000 years, waves, currents and tides control sedimentation. • 1,000,000 years, sea level lowered by glaciation controls sedimentation and cause rivers to deposit their sediments at the shelf edge and onto the upper continental slope. • 100,000,000 years, plate tectonics determines the type of margin that develops and controls sedimentation. 4-2 Sedimentation in the Ocean
What’s in there? • Forams • Coccoliths • Radiolarians (and other Protozoans) • Diatoms and other Phytoplankton (shells) • Fecal Pellets and “Dead” things (marine snow)
Major pelagic sediments in the ocean are red clay and biogenic oozes. Foraminifera Diatoms “Marine Snow”
What do you get? …What geologic structures? and where?
Global Deep-Sea Deposits Sedimentation Rates
If influx of terrigenous sediment is low and the water is warm, carbonate sediments and reefs will dominate. Distribution of Carbonate Shelves
Deep-sea Sedimentation has two main sources of sediment: • External – terrigenous material from the land • Internal – biogenous and hydrogenous from the sea.
