GEOL 440
Sedimentology and stratigraphy:
processes, environments and
deposits
Lectures 24 and 25 : Turbidity
currents and deep sea environments
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In these Lecture Slides, the Lecturer has discussed the following key points in his class of Stratigraphy : Turbidity Current, Delta Front, Shelf, Canyons, Sinuous Turbidity, Current Channel, Slope Failures, Storm Events, Rip Currents, Inception
Typology: Slides
2012/2013
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GEOL 440
Sedimentology and stratigraphy:
processes, environments and
deposits
Lectures 24 and 25 : Turbidity
currents and deep sea environmentsDocsity.com
Aims: to examine and detail…
- Turbidity currents
- Turbidites
- Turbidity current anatomy: Head, body, tail
- Surge or sustained flows?
- Flow unsteadiness
- Flow non-uniformity
- Turbidite facies and the Bouma sequence
Docsity.com
What is a turbidity current?
“A flow induced by the action of gravity on a fluidal, turbid
mixture of fluid and suspended sediment, by virtue of the
density difference between the fluid and the ambient flow.”
- Movement occurs due to the different densities.
- Gravity & density drive these flows. Particles are held in turbulent suspension, Fr: >1 to <1, Re: > 2000.
- They can travel in excess of 10 m/s
- Scales: puddles to oceans. Docsity.com
What is a turbidity current?
lofting plume
ramb1<rflow<ramb
descending plume
rflow>ramb
overflow
rflow<ramb
underflow rflow>ramb
Types of turbidity (density) current
Thermo-/pycnocline
interflow
ramb1<rflow<ramb
ramb
ramb
Hyperpycnal
Hypopycnal
Mesopycnal or
From Leeder (1999) Docsity.com
What is a turbidity current?
The deposit of a turbidity current is called a turbidite
Ross Bay, Co. Clare, Eire Docsity.com
Turbidity currents are one example of a more
general set of density flows
Other density current examples include: pyroclastic flows, dust storms, river plumes Docsity.com
What does a turbidity current look like?
- The head is generally thicker than the rest of the flow.
- It is here that turbulence is often the greatest.
- The greatest amount of mixing with ambient fluid occurs here.
- The head moves slower than the rest of the flow.
From Hacker et al., (1996)
Slumping phase
Most concentrated flow
Back catches the front, the flow runs out of dense fluid & ultimately stops
Density contours
Mixing