1 Deep-Water Depositional Systems Class reading from Boggs, Principles of Sedimentology and Stratigraphy : p.349 - 364. In the submarine environment, particularly the continental slope, patterns of sediment erosion and deposition are governed to sediment- gravity flows. Since these currents move through water, gravity drives these flows by acting on the “excess” density of the water+sediment mixtures; that fraction of the bulk density that exceeds the density of water. Turbidity Currents (~ <10 % suspended sediment by volume) Debris Flows (~ 50:50 sediment and water by volume)
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Deep-Water Depositional Systems · Deep-Water Depositional Systems Class reading from Boggs, Principles of Sedimentology and Stratigraphy: p.349 - 364. In the submarine environment,
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Deep-Water Depositional Systems
Class reading from Boggs, Principles of
Sedimentology and Stratigraphy: p.349 - 364.
In the submarine environment, particularly the continental slope, patterns of sediment erosion and deposition are governed to sediment-gravity flows. Since these currents move through water, gravity drives these flows by acting on the “excess” density of the water+sedimentmixtures; that fraction of the bulk density that exceeds the density of water. Turbidity Currents
(~ <10 % suspended sediment by volume)
Debris Flows(~ 50:50 sedimentand water by volume)
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A type example of a deepwater-depositional system; the Brazos-Trinity Slope System
(Prather et al., in press)
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Topography, depositional patterns and structural deformation associated with the Brazos-Trinity slope system and its 5 minibasins.
Active structural deformation is the product of motion of the Luann Salt.
Location map and seismic cross-section through the B-T system. (Pirmez et al., in press)
Badalini et al., 2000
Seascape development is often the product of competition
between deforming substrate and sediment-transporting
flows (note spatial change in patterns of deposition and
erosion below).
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Seismic section through shelf-edge delta
delivering sediment to Basin 1 during the
last sea-level lowstand. (Prather et al., in press)
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(above) Seismic cross section through
Basin 2 deposit. All of this sediment
accumulated during the past 20,000 yrs.
(left) Maps of deposit thickness
Figure (a) = the 6a deposit shown in
cross section above.
Figure (b) = the 6b deposit shown in
cross section above.
Figures (c) & (d) = the 6c deposit shown
in cross section above.
Notice the changes in sedimentation
pattern as deposits fill in the pre-existing
Basin 2 topography.
Basin 2 of the
linked, Brazos-
Trinity Slope
System.
(Prather et al., in press)
(Beaubouef & Friedmann, 2001)
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Low Sediment-Concentration Turbidity Currents
(~ < 1 % suspended sediment by volume)
High Sediment-Concentration Turbidity Currents
(~1 - 10 % suspended sediment by volume)
Debris Flows(~ 50:50 sediment
and water )
Sediment-Gravity Flows
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Initiation and Evolution of Sediment-Charged Submarine
Flows
Hyperpycnal Flow
SlopeFailures
Low-Sediment Concentration
High-Sediment Concentration
Slide and Slump
DebrisFlow
Extensive InternalDeformation
Minor InternalDeformation
TurbidityCurrent
Sediment Gravity Flows
River flows with high suspended-sediment concentration can be
sufficiently dense to plungeunderneath seawater and
continue down-slope
Slope-Failure Triggers:1) Waves and currents of
large storms2) Unusually low tides3) High internal pore
pressures4) Earthquakes5) Tectonically steepened
slopes
There are modern examples of failures in deposits with surface slopes as small as 0.1 degrees.