Presentation on theme: "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."— Presentation transcript:
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 –accumulation of economic resources –geologic hazards –climate change –environmental management
Control of Margin Dynamics by Sediments How would margin dynamics be different if there were no sediments? –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 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?
Sediment Controls on Rifting Margins 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 If deltas are home to half a billion people, can MARGINS II really ignore them? Is Eustasy Really Dead? Is there a difference in margin evolution during icehouse versus greenhouse worlds? How are biogeochemical processes and budgets influenced by margin dynamics and vice versa? 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
From Sanje 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. 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) 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). 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. 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. 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..
(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 Sea- Level 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).