Transcript PPT - Margins Program

Control of Margin Dynamics
by Sediments
Part I: Rudy Slingerland
Part II: Dave Mohrig
Part III: Sanjeev Gupta
and also see
Lou Derry on weathering fluxes
Alex Densmore on sediment routing
&
Various White Papers
Two Visions for Sediments in
MARGINS II
• From the Decadal Review Committee
(DRC) Report
Two Visions for Sediments in
MARGINS II
• From the MARGINS Steering Committee [letter of
response to DRC, March 2009]
– “…the Steering Committee envisions a successor program
that will investigate the coupled geodynamic, surficial, and
climatic processes that build and modify continental margins
over a wide range of timescales (from s to My).”
• applications to margin evolution and dynamics
• construction of stratigraphic architecture
• implications for
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accumulation of economic resources
geologic hazards
climate change
environmental management
Control of Margin Dynamics by
Sediments
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How would margin dynamics be different if there were no sediments?
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Would plate tectonics operate differently?
Would volcanic processes on margins be appreciably changed?
Would continents rift differently?
Without a sedimentary record would we even know?
Three Areas of Margins Research
– Sediment Controls on Subduction Processes
– Sediment Controls on Thermo-mechanical Behavior of Rifting Margins
– Morphodynamic Sediment Transport Systems on Margins: Feedbacks and
Emergent Behavior
Sediment Controls on Subduction
Processes
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Does thick versus thin sediment in
subduction zones create 2 to 4 million year
feedbacks between ingested sediment,
dehydration of clays, and subsequent
crustal melting?
Is correlation of Andean volcanism with
climate due to increased sediment fluxes to
the trench causing increased melt rates?
Are sediment-rich subduction zones more
prone to large earthquake ruptures and
tsunamis? (white paper by D. Harry, R.
Stern, E. Anthony, G. Keller, I. Norton, J.
van Wijke)
If sediment flux really matters, then how do
sediment routing systems control margin
growth, and how does margin growth control
the sediment routing systems?
http://voyagerstories.files.wordpress.com/2009/02/rock-cycle.jpg
Sediment Controls on Rifting
Margins
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Is rift margin evolution strongly determined
by a feedback system between sediment
fluxes, heat fluxes, and lithospheric
dynamics?
How much do climate and surface
processes affect the transition from rifting
to seafloor spreading? (white paper by B.
Dorsey, M. Oskin, P. Umhoefer, R.
Arrowsmith, P. Lonsdale, N. Driscoll)
Do feedbacks between rifting and
landscape evolution create a predictable
timing, location, and amount of basin-fill?
Morphodynamic Sediment
Transport Systems, Feedbacks,
and Emergent Behavior
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If deltas are home to half a billion
people, can MARGINS II really
ignore them?
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Is Eustasy Really Dead?
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Is there a difference in margin
evolution during icehouse versus
greenhouse worlds?
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How are biogeochemical processes
and budgets influenced by margin
dynamics and vice versa?
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Do margin dynamics change as life
evolves?
Points of Discussion
• There is compelling quantitative science to be done on coupled
geodynamic and sedimentary processes that build and modify
continental margins
• If projects are selected properly the new knowledge will allow
improved prediction of:
• accumulation of economic resources
• geologic hazards
• environmental change
• The societal significance of margin dynamics and the need for
broad interdisciplinary science teams justify a special program
with sequestered funding
Extras
From Sanje
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1. How you can use stratigraphy to reconstruct (the only way yuo can) the 3d evolution of tectonic displacement fields in basins that the first order has been done but this needs to significantly improve. Sediments and stratigraphy are excellent strain markers
but the details of how that stratigraphy is constructed are actually quite important and we need to understand this, ie sediment just
can't be taken away by geophysicists.
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3. Sedimentary architecture. here i wanted to explain why it is important to understanding sedimentary architecture - how we can
use it to reconstruct the kinematics of surface systems, and why this is necessary if we are read the archive for external forcing.
Why we need to think timescales, and why there may be more of a record than the tectonics community may have thought (here i
am trying to be positive - my pint is going to be 3/4 full). I was going to mix in here some SAFL experiments esp the one they are
running now and field examples. I was going to show the geometric forms that make margins are scale invariant (to a certain
extent)
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Here i was going to say soemthing about climate. But i was going to stress that more interesting than reconstructing past climate
change absolute is how the Earth's surface system responds to climate change. I have to think about this (a lot).
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I was supposed to talk about feedbacks etc etc but i just don't know enough about these - there is a paper by roger buck on this
that has got the community excited but its very early days yet here unless either of yuo know different.
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I thought i might end by large-scale tectonic processes.. the current excitement is about large-scale mantle processes - they key
here is that these beautiful models that people generate are ONLY testable with the long-term strat record.
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Need to bring life in here somwehere.. ie. there has been some work that suggest the main control on speciation and exitinction
are shelf evolution through time - drowning/exposure. Another recnt Nature paper on evolution suggest that the the idea of slow
gradual evolution is rubbish and that the key events are things like orogenesis and drainage evoltuion p and this paper is by
mathematical biologists..
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(this one is the least compelling on my recommended list, but perhaps some useful references)
3. Surface processes, weathering fluxes and CO2 sinks in arc terranes
Authors: L. Derry, H. Schopka
5. The Role of Climate, Surface Processes, and Sedimentation in Continental Rifts
and the Transition from Rifting to Seafloor Spreading
Authors: B. Dorsey, M. Oskin, P. Umhoefer, R. Arrowsmith, P. Lonsdale, N. Driscoll
(recognizes the utility of seismic data and strat to constrain timing of subduction initiation)
8. The Initiation of Subduction: From kinematics to dynamics
Authors: M. Gurnis, R. Stern, O. Ishizuka, M. Reagan, J. Pearce, R. Sutherland, J. Gill
10. Continental Breakup and Formation of Rifted Margins: The Gulf of Mexico as a
Natural Laboratory
Authors: D. Harry, R. Stern, E. Anthony, G. Keller, I. Norton, J. van Wijke
(argue that sediment-rich subduction zones are prone to large earthquake ruptures and tsunamis)
12. Selection Criteria for Future Geohazards-Motivated Research under the NSF
MARGINS Successor Program
Authors: S. Kirby, R. von Huene
14. Glacial-Marine Sedimentation as a Recorder of Tectonic, Climatic and SeaLevel Dynamics on Active Continental Margins
Authors: C. Nittrouer, B. Hallet
15. Links between Quaternary volcanism, neotectonism and upper-plate structural
style in the Aleutian arc: new perspectives
Authors: C. Nye, K. Keranen, P. Decker, J.Freymueller
Vision 0
• MARGINS II will investigate the coupled
geodynamics, Earth surface processes, and climate
interactions, that build and modify continental
margins over a wide range of timescales (from s to
My), with applications to margin evolution,
construction of stratigraphic architecture,
accumulation of economic resources, and associated
geologic hazards and environmental (land-use)
management.
• Integrated activities: Structure & tectonics,
geochemistry, geophysics, sedimentology &
stratigraphy, incorporating:
– Field studies
– Experimental/analytical studies
– Numerical modeling
Vision xI
• MARGINS-II will investigate coupled
geodynamics and Earth surface processes
that build margins at millenial and greater
timescales.
– Note: Excludes problem of compaction induced
subsidence at century scales, wetlands restoration
by distributary manipulations, and arctic crustal
evolutions due to global warming.
Vision xII
• MARGINS-II will integrate all societally
relevant processes and time-scales operating
at margins as long as they lead to
improvements in hazards prediction,
environmental management, or general
scientific understanding.
NSF CHARGE
• 1) compelling science issues that the
community would like to see addressed in a
possible successor program;
• 2) thematic vs “focus-site” (or mixed)
approaches to margins research, both pros
and cons; and
• 3) justifications for a special program with
sequestered funding (rather than a “directed”
program within Core).