DEEPWATER%20TURBIDITY%20CURRENT%20DYNAMICS:%20INCEPTION,%20EROSION%20AND%20DEPOSITION

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DEEPWATER TURBIDITY CURRENT DYNAMICS INCEPTION,
EROSION AND DEPOSITION Gary Parker Dept. of
Civil Envr. Engrg. and Dept. of Geology,
University of Illinois Presented at SEPM
Luncheon, AAPG Conference, Houston, Texas, April
11 2006
Stepped profile, Niger Margin From Prather et al.
(2003)
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WHAT IS A TURBIDITY CURRENT? Working definition

• A turbidity current is a member of the class of
  dense bottom flows that includes thermohaline
  bottom flows (e.g. Straits of Gibraltar).

• The presence of a dilute suspension of
• sediment in the water of a turbidity current
• renders it slightly heavier than the ambient
  water.

• Gravity pulls the sediment downslope, and the
  sediment then pulls the water with it.

• A turbidity current differs from a submarine
  debris flow in that the debris flow slurry is
  much heavier than the ambient water.

• A turbidity current differs from a thermohaline
  underflow in that it is free to exchange sediment
  with the bed.

• A turbidity current is the subaqueous analog of
  a river.

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SO BY MY DEFINITION, A LAMINAR UNDERFLOW DRIVEN
BY FINE SEDIMENT IS A TURBIDITY CURRENT
For what its worth, Metivier, Lajeunesse and
Cacas (2005) have excavated experimental
submarine canyons with laminar saline underflows.
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AN EXPERIMENTAL TURBIDITY CURRENT
Video clip
Violet, Parker and Beaubouef (in prep.)
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ANOTHER EXPERIMENTAL TURBIDITY CURRENT
Video clip
Cantelli, Johnson, White and Parker (submitted)
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A RECENT SUCCESS IN MEASURING TURBIDITY CURRENTS
IN MONTEREY SUBMARINE CANYON
Xu, Noble, Rosenfeld, Paull (USGS, NPS, MBARI)
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• Sustained event lasted 5 - 8 hours
• Max. velocity 1.9 m/s
• Thicker downcanyon?
• Not caused by storm or hyperpycnal flow (failure
  of dredge spoil?)

Xu, Noble, Rosenfeld, Paull (USGS, NPS, MBARI)
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THERE ARE MULTIPLE TRIGGERING MECHANISMS!

• VERIFIED MECHANISMS
• Storms (Inman, Nordstrom and Flick, 1976)
• Sudden deltaic slope failures (excess pore
  pressure, earthquakes etc.) (Hay, 1987)
• Hyperpycnal flows (river plunging Mulder and
  Syvitski, 1995)
• Breaching retrogressive slope failure (van den
  Berg, Gelder and Mastbergen, 2002)
• Conversion from submarine debris flows (Norem,
  Locat and Schieldrop, 1990)

• REASONABLE HYPOTHESIZED MECHANISMS
• Internal waves breaking on the continental slope
  (Caccione)
• Double-diffusive mechanism (fresh, warm
  sediment-laden water flowing into cold brine)
  (Parsons, Bush and Syvitski, 2001)

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HYPERPYCNAL FLOWS
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PLUNGING
Plunging in Lake Lugano, Switzerland (De Cesare,
1999)
Plunge line in Lake Lillooet Lake, Canada (Best,
Kostaschuk, Peakall, Villard and Franklin, 2005)
Video clip
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HYPERPYCNAL FLOWS AND ACTIVE MARGINS
In order for fresh water to be denser than sea
water, the volume concentration of suspended
sediment must exceed about 43,000 mg/liter.
It is extremely uncommon for a river to carry
such a high charge of sediment!
Best place to look for such streams (other than
Yellow River, China) Rapidly uplifting active
margins!
16 of the rivers listed by Mulder and Syvitski
(1995) that go hyperpycnal at least once per 100
years are in Taiwan.
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ARE LARGE RIVERS ON PASSIVE MARGINS PASSING
THROUGH gt 1000 KM OF LOWLANDS BEFORE REACHING
THE SEA LIKELY TO EVER REACH HYPERPYCNAL
CONDITIONS?
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NO!
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THE PASSAGE OF A RIVER THROUGH A LONG LOWLANDS
REACH VASTLY REDUCES THE SUSPENDED SEDIMENT
CONCENTRATION
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HYPERPYCNAL FLOWS ARE NOT LIKELY RESPONSIBLE FOR
THESE MEANDERING CHANNELS, WHICH LIKELY REQUIRED
SUSTAINED FORMATIVE FLOWS
Mississippi Submarine Fan (Weimer, 1991).
Indus Submarine Fan (Kenyon et al., 1995)
Amazon Submarine Fan (Pirmez, 1995)
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NOT TO WORRY! THERE ARE OTHER WAYS OF MAKING
SUSTAINED TURBIDITY CURRENTS
Breaching a sustained retrogressive failure in
fine sand leading to sustained turbidity
currents (van den Berg, Gelder and Mastbergen,
2002)
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A SLOW NATURAL BREACH FAILURE LAUNCHES A BOAT IN
THE RHINE DELTA
Van den Berg, Gelder and Mastbergen (2002)
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IN ADDITION, A TURBIDITY CURRENT CAN START OUT
SMALL AND GET BIG BY THE PROCESS OF IGNITION
(SELF-ACCELERATION)
Current entrains bed sediment, gets heavier, is
pulled downslope more strongly by gravity,
accelerates, entrains more sediment in a
self-reinforcing cycle (Parker, Fukushima and
Pantin, 1986 Pratson, Imran, Parker, Syvitski,
Hutton, 2000)
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IGNITION IS A GOOD WAY TO BUILD UP SUFFICIENTLY
SWIFT CURRENTS TO EXCAVATE SUBMARINE CANYONS
Head of Monterey Canyon not located at river
mouth. Image from D. Smith.
Turbidity current may be triggered by storms or
breaching and then may self-accelerate.
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AND BESIDES, HYPOPYCNAL FLOWS (WHICH DONT
GENERATE TURBIDITY CURRENTS) DONT GET THE
RESPECT THEY DESERVE
Hypopycnal flows along the Adriatic margin of
Italy image from J. Syvitski.
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WHY DO CONTINENTS ALWAYS HAVE RINGS AROUND THE
COLLAR (MARGINS?)
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AT LEAST PART OF CONTINENTAL SHELVES ARE
CONSTRUCTED SUBAQUEOUSLY (AND ARE NOT SIMPLY
DROWNED LOW-STAND COASTAL PLAINS)
Actively prograding clinoform near mouth of the
Fly River, Papua New Guinea image from Crockett
and Nittrouer
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DOES SALT WATER MAKE A DIFFERENCE?
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PROXIMAL DEPOSITION FROM HYPOPYCNAL FLOWS
ALONGSHELF REWORKING CONTINUOUS SHELF!
Salt causes Margins RANK SPECULATION
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WAVE-CURRENT ACTION STIRS UP MUD ON OUTER SHELF,
CREATING WEAK TURBIDITY CURRENTS WHICH DEPOSIT
BELOW WAVE BASE, PROGRADING THE CLINOFORM!
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STORM-GENERATED SHEET (LINE) TURBIDITY CURRENTS
MAY BE RESPONSIBLE FOR MARGIN CONSTRUCTION
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MUDDY SHEET TURBIDITY CURRENTS APPEAR TO PLAY A
MAJOR ROLE IN SHAPING THE BRUNEI MARGIN
Muddy deposits uniformly blanket zone of mud
diapirism at base of margin
Straub, Mohrig and Pirmez in progress
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MUD DRAPES THE ENTIRE TOPOGRAPHY
Seafloor C.I. 8m
Slightly suppressed deposition in the lows allows
for channels to be constructed in a
net-depositional environment!
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SHEET TURBIDITY CURRENTS CAN LIKELY FOCUS IN LOW
POINTS AND CARVE NET-EROSIONAL CHANNELS
California margin
New Jersey margin
Theory Izumi (2004) Images Pratson and Haxby
(1997)
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DOMINANT EROSIONAL CHANNELS FORM CANYONS
FUNNELING SHELF SEDIMENT SOURCES TO DEEP WATER
Focusing self-acceleration excavates a royal
pathway to deliver sand into deep water!
Savoye, Cochonat et al. (2000)
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BUT THE ROUTE TO DEEP WATER MAY NOT BE SO SIMPLE
Diapirism and other tectonic factors may lead to
stepped profiles.
Stepped profile, Niger Margin From Prather et al.
(2003)
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TURBIDITY CURRENTS SLICE AND FILL THEIR WAY
THROUGH THE MAZE CREATED BY SALT DIAPIRISM
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THE CHANNEL PROFILE HAS BEEN SMOOTHED BY FILLING
IN THE BASINS AND INCISION IN THE RIDGES
Basin IV does not yet have an outlet.
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HOW DO TURBIDITY CURRENTS FILL DIAPIRIC
MINIBASINS?
Video clip
Toniolo, Lamb and Parker (2006)
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EVOLUTION OF THE DEPOSIT IN A MINIBASIN
sand
mud
wall
Violet, Parker and Beaubouef (in prep.)
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THE FORESET?
Violet, Parker and Beaubouef (in prep.)
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A FLUVIAL DELTA
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THE CONCEPT OF AN INTERNAL (DEEPWATER) DELTA
RANK SPECULATION
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AN INTERNAL (DEEPWATER) DELTA IN A MINIBASIN?
Sand-rich topset?
Beaubouef, Van Wagoner, Adair (2003)
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THE ROLE OF THE KNICKPOINT GENERATED BY INCISION
DOWNSTREAM
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TURBIDITY CURRENTS CAN GENERATE KNICKPOINTS
California margin near Santa Barbara
Yu, Cantelli, Marr, Pirmez, OByrne, Parker (2006)
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TURBIDITY CURRENTS CAN GENERATE KNICKPOINTS
Video clip
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CONCEPTUAL MODEL FOR FILL AND SPILL
Parker and Beaubouef (in prep)
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NUMERICAL MODELING OF FILL-AND-SPILL IN A
SEQUENCE OF BASINS
Kubo, Syvitski, Hutton, Paola (2005)
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SELF-CONFINEMENT AND LEVEE CONSTRUCTION
Turbidity currents are adept at confining
themselves between levees.
Channel on Amazon Submarine Fan Damuth and Flood
(1985)
Toyama Submarine Channel Kubo and Nakajima (2002)
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LEVEE CONSTRUCTION IN THE LABORATORY
Straub, Mohrig, Buttles, McElroy (in press)
outer-bank runup exceeds that predicted by
standard centrifugal superelevation
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NUMERICAL MODELING OF THE INITIATION OF
SELF-CONFINEMENT
net depositional everywhere
net erosional in channel center
Imran, Parker and Katopodes (1998)
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THE PROGRESS WE HAVE MADE ON SELF-CONFINEMENT
SINCE 1998
Video clip
Numerical model of Sun, Li, Abreu, Dunn (2006)
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THE PROGRESS WE HAVE MADE ON SELF-CONFINEMENT
SINCE 1998
Physical model of Yu, Cantelli, Marr, Pirmez,
OByrne, Parker (2006)
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CHANNEL MEANDERING
An increasing body of evidence suggests that
submarine meandering channels do most of the
things that meandering rivers do (but in
different degrees).
Abreu, Sullivan, Pirmez, Mohrig (2006)
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BUT THERE IS STILL A LOT OF DISAGREEMENT ABOUT
PROCESSES
Kassem and Imran (2004) The circulation patterns
observed in a submarine meandering channel
clearly differ from the familiar single cell
helical flow in the cross section of a sinuous
open channel. In the two confined cases
considered here, multiple cells of circulations
have formed.
Note the experimental data of Mohrigs MIT group
is presently being used to validate the numerical
model of Imrans South Carolina group.
Corney, Peakall, Parsons, Elliot, Amos, Best,
Keevil, Ingham (2006) Kassem and Imran contest
that the structure of secondary flow in submarine
channel bends is very similar to subaerial
open-channel bends. the models of Kassem
Imran (2004) were not validated with experimental
dataThe present results contradict the
unvalidated numerical modelling of Kassem Imran
(2004).
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THE ANSWER MAY BE IN THE ISSUE OF SELF-CONTAINMENT

• St. Paul on self-containment
• I say therefore to the unmarried,it is good
  for them if they abide even as I.

• But if they cannot contain themselves, let them
  marry for it is better to marry than to burn.

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SELF-CONTAINMENT
Submarine meandering channels contain themselves
between levees over 100s 1000s of km and
scores 100s of bends.
Bengal Fan Schwenk, Spiess,Hubscher, Breitzke
(2003)
Zaire Fan Savoye, Cochonat et al. (2000)
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SELF-CONTAINMENT IS ESSENTIAL IF A TURBIDITY
CURRENT IS TO RETAIN ITS COHERENCE OVER 1000 KM
OF RUNOUT
The channel must mature so that it carefully
moderates channel/levee deposition rates the from
the turbidity currents it passes.
Pirmez and Imran (2003)
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PERHAPS OUR EXPERIMENTAL/NUMERICAL MEANDERING
CHANNELS/TURBIDITY CURRENTS ARE REALISTIC, BUT
STILL TOO ADOLESCENT TO BE PROPERLY
SELF-CONTAINING
So that different studies look at different
periods of adolescence and get different answers.
Leeds
MIT
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AND NOW FOR MY HOBBY CYCLIC STEPS A UNIVERSAL
BEDFORM OF FROUDE-SUPERCRITICAL FLOW IN RIVERS
AND TURBIDITY CURRENTS
Taki and Parker (2005) Sun and Parker (2005)
Fildani, Normark, Kostic and Parker (2006)
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SEDIMENT WAVES/ANTIDUNES
California margin image courtesy W. Normark
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THE SEDIMENT WAVES INVARIABLY MIGRATE UPSTREAM
IN ORDERLY TRAINS
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CYCLIC STEPS ARE RELATIVES OF ANTIDUNES, BUT
HYDRAULIC JUMPS LOCK STEPS IN TRAIN
Cyclic steps in tailings basin of iron mine,
Labrador, Canada
roll waves
flow
cyclic steps
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Video clip
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BILL NORMARK HELPED US IDENTIFY THEM IN THE
SUBMARINE SETTING
Levee of outer bank of Sheperd Meander, Monterey
Submarine Channel
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THE SEDIMENT WAVES ARE NET-DEPOSITIONAL CYCLIC
STEPS, AND THE MONTEREY EAST CHANNEL SHOWS
EROSIONAL CYCLIC STEPS
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SELF-FORMED SUBMARINE CYCLIC STEPS FORMED BY A
TURBIDITY CURRENT OVERFLOWING THE LEVEE OF THE
MONTEREY CHANNEL
The numerical model of Kostic and Parker (2005)
predicts both net-erosional and net-depositional
cyclic steps created by turbidity currents.
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QUESTIONS, COMMENTS OR CRITICISMS?