TA2910 09 - Deep-marine Sands

8/10/2019 TA2910 09 - Deep-marine Sands

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Challenge the future

DelftUniversity ofTechnology

M.E. Donselaar

Deep-marine sand deposits


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Sedimentary environments

Continental: fluvial (braided, meandering)

aeolian

lacustrine

Coastal: deltaslinear (clastic, carbonate)

Marine: shelf

deep marine sands

pelagic


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Deep marine sands

Sands that have moved down slope from the shelf andcontinental slope under the influence of gravity (gravity

flows)


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Outline

Morphology

Processes

Facies types and sedimentary structures

Fan models Sequences

Sequence-stratigraphy


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Deep marine sands - Occurrence


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Deep marine sandssediment source

Submarine canyons erode up

dip into shelf

Shelf edge collapse

Continental slope failure Fluvial bypass of shelf during

lowstand

At the base-of-slope: fan-

shaped sediment accumulation:Submarine fan


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Submarine fans: Morphology - 1

Galloway & Hobday (1996)

point source

arcuate line source

line source (shelf edge)

line source (mass wasting)


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Monterey submarine canyon

http://userpage.fu-berlin.de/~voelker/Vorlesung_Meeresgeologie/sediment2.html


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Indus & Ganges submarine fans


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Deep marine sands: Slope failure



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Relation bathymetryfan shape

Syn-sedimentary tectonics

Salt diapirism

Batholiths

Positive relief by previous fans


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Influence on fan shapeSyn-sedimentary tectonics

1: Short, wide, fault-conditioned slope fan

2: Elongate fault-conditioned basin-floor fan

3: Lateral imbrication of basin-floor fan


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Fault-conditioned basin floor fan: FramField (U. Jurassic, Horda Platform)

I.1a

I.1bI.2

I.3

II.4

II.4

II.3

II.2

II.1

35/11-8S 35/11-9

2.5 km

125m

80m

From: Visser (2005)


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Fault-conditioned sediment transportpath

Modified from Williams (1993)


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Salt diapirism

Mini-basins created by

salt-diapir controlled

bathymetry

Turbidite flows

concentrated in thesemini-basins

Reservoirs in GoM,

offshore Angola, Brazil

http://www2.petrobras.com.br/ri/pdf/2007_Formigli_Miami_pre-sal.pdf

Santos Basin, offshore Brazil


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Deep-marine sands:Transport & depositional processes

Shanmugan (1996)


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Subsequent stages of gravity gliding

Slide

Coherent mass with preserved internal

organization

Slump

Coherent mass, but plastic

deformation of internal structure

Debris flow

Incoherent mass: internal organization

destroyed

Turbidity current

Newtonian fluid with sediment in

suspension


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Slides

Martinsen (1989)


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Slumps

Martinsen (1989)


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Slump - outcrop example


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Debris flow

Plastic flow

Sediment & water fullymixed

Cohesive strength of matrixis main clast-supportmechanism

Buoyancy

http://www.usask.ca/geology/classes/geol243/243notes/243week4a.html


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Debris flow

Plastic flow can freeze = main

sand body just stops on the

slope.

Top of debris flow: gradual

change to suspension

http://faculty.gg.uwyo.edu/heller/sed_video_downloads.htm


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Liquefied flow

Metastable grain packing

texture disturbed, hence:

Closer grain packing creates

excess pore fluid

Fluid escape, hence texture

disturbed, and sediment-water

mixture behaves as rheological

fluid

On slope: flow Freezing



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Liquefied flowoutcrop example

Laminated sand

Dish structures

Fluid escape structures


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Liquefied flowfluid escape


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Turbidity current

Suspension of sediment

Sustained by fluid turbulence



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Turbidity current

Shanmugam (1997)


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Turbidite flow - 1

Gradual vertical and

downstream change from

graded traction carpet (dark

colour) to high-density

suspended sand (light colour) Traction carpet: non-Newtonian

(pseudo-plastic) flow

Creation of turbulent flow at

head of flow


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Turbidite flow - 2

Fan-shaped turbidity flow in

flume experiment


Sedimentary


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Sedimentarystructures

Lowe (1982)


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Bouma sequence

e: Pelagic and hemipelagic mud

d: Laminated silt (lower flow

regime)

c: Cross-laminated sand (lower

flow regime)

b: Parallel laminated sands

(upper flow regime)

a: Massive sand and granules

(upper flow regime) Scoured base with tool marks,

flutes, etc.

Bouma (1962)


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Bouma sequence: spatial distribution

http://www.usask.ca/geology/classes/geol243/243notes/243week4b.html


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Bouma turbidite


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Bouma turbidite: proximal

a

b

c


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Bouma turbidite: distal

c

de

d

e

e

Submarine fan model


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Submarine fan modelMutti & Ricci Lucchi (1972)

Slope: feeder channel

Inner fan

Channel fill deposits

Incised channels

Middle fan

Bifurcating, multiple channels Channel-levee complexes

Outer fan

Mounded lobes

Autocyclic channel avulsion and lobeshifting

Basin plain

Fine-grained sheet turbidites

Mutti & Ricci Lucchi (1972)

Submarine fan model


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Submarine fan modelHypothetical prograding fan sequence

Mutti & Ricchi Lucchi (1972)


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Proximal to distal changes

Fan sedimentation towards equilibrium profile

Proximal:

Slope is steep

Channels erode into fan Distal:

Slope gentle

Gradual change from erosional to aggradational processes


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Turbidite channels


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Turbidite channelsLithology and channel shape



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Examples of sequences & log shapes


Deep-marine sands and sequence


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Deep marine sands and sequencestratigraphy

Relative sea level fall:

Shelf (partly) exposed, hence loss of accommodation

Sediment bypasses directly to slope and basin

Creation of lowstand fan Lowstand:

Rate of relative sea level change low

Creation of lowstand wedge (aggradational)

Relative sea level rise: Shelf gradually flooded, hence strong increase of

accommodation (storage capacity)


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Sequence stratigraphy - HST

Posamentier et al.(1988)


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Sequence stratigraphy - LST



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Sequence stratigraphy - LST



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Sequence stratigraphy - TST



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Sequence stratigraphy - HST



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Links

http://faculty.gg.uwyo.edu/heller/sed_video_downloads.htmhttp://faculty.gg.uwyo.edu/heller/sed_video_downloads.htmhttp://faculty.gg.uwyo.edu/heller/sed_video_downloads.htmhttp://faculty.gg.uwyo.edu/heller/sed_video_downloads.htm


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Compulsory reading

Nichols Chapter 16:

Sections 16.1 - 16.2

TA2910 09 - Deep-marine Sands

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Transcript of TA2910 09 - Deep-marine Sands