workshop on global bathymetry for oceanography, geophysics, and climatology24-26 october 2002...

Workshop on Global Bathymetry for Oceanography, Geophysics, and Climatology 24-26 October 2002

MARGINS Interests in MARGINS Interests in Improved Resolution Improved Resolution

Altimetry Derived Gravity Altimetry Derived Gravity ObservationsObservations

Dale SawyerDale SawyerDept. of Earth ScienceDept. of Earth Science

Rice UniversityRice University

Houston, TXHouston, TX


What is MARGINS?What is MARGINS? The MARGINS Initiative seeks to understand the The MARGINS Initiative seeks to understand the

complex interplay of processes that govern continental complex interplay of processes that govern continental margin evolution. The objective is to develop a self-margin evolution. The objective is to develop a self-consistent understanding of the processes that are consistent understanding of the processes that are fundamental to margin formation and evolution. The fundamental to margin formation and evolution. The MARGINS approach involves concentration on several MARGINS approach involves concentration on several study areas targeted for intense, multidisciplinary study areas targeted for intense, multidisciplinary programs of research in which an ongoing dialogue programs of research in which an ongoing dialogue among field experiment, numerical simulation and among field experiment, numerical simulation and laboratory analysis researchers is axiomatic. The plan is laboratory analysis researchers is axiomatic. The plan is to investigate active systems as a whole, viewing a to investigate active systems as a whole, viewing a margin not so much as a “geological” entity of margin not so much as a “geological” entity of divergent, translational or convergent type, but more in divergent, translational or convergent type, but more in terms of a complex physical, chemical and biological terms of a complex physical, chemical and biological system, subject to a variety of influences. The processes system, subject to a variety of influences. The processes that fundamentally govern the evolution of margins that fundamentally govern the evolution of margins include lithospheric deformation, magmatism and mass include lithospheric deformation, magmatism and mass fluxes, sedimentation, and fluid flow. fluxes, sedimentation, and fluid flow.


All MARGINS Focus Areas are within the All MARGINS Focus Areas are within the latitude range (55S to 55N) Walter Smith latitude range (55S to 55N) Walter Smith indicated was desirable for data quality.indicated was desirable for data quality.

Altimetry derived gravity and bathymetry data Altimetry derived gravity and bathymetry data will be used to set the plate tectonic framework will be used to set the plate tectonic framework for all the MARGINS studies. for all the MARGINS studies. Proposed higher Proposed higher resolution desirable, but not essential.resolution desirable, but not essential.

If bathymetry is an important observable in a If bathymetry is an important observable in a MARGINS focus area, the program will likely MARGINS focus area, the program will likely obtain multi-beam data throughout the study obtain multi-beam data throughout the study area. Altimetry derived gravity and bathymetry area. Altimetry derived gravity and bathymetry data will continue to play a role in extending data will continue to play a role in extending bathymetric coverage outside the immediate bathymetric coverage outside the immediate study area. study area. Proposed higher resolution Proposed higher resolution desirable, but not essential.desirable, but not essential.


Altimetry derived gravity data can be Altimetry derived gravity data can be combined with multi-beam bathymetry to combined with multi-beam bathymetry to invert for subsurface structure on margins. invert for subsurface structure on margins. I envision this to be the primary essential I envision this to be the primary essential use of altimetry data by the MARGINS use of altimetry data by the MARGINS program, and the best argument for program, and the best argument for increasing the resolution of the dataincreasing the resolution of the data. .

Data security classification worries me, Data security classification worries me, because MARGINS needs the gravity data, because MARGINS needs the gravity data, not “a statistical description of the fractal not “a statistical description of the fractal nature of the seafloor.”nature of the seafloor.”

I see this method as most likely to be I see this method as most likely to be important for the Rupturing Continental important for the Rupturing Continental Lithosphere part of MARGINS.Lithosphere part of MARGINS.


Why RCL?Why RCL?

Rifted fault-bounded blocks of Rifted fault-bounded blocks of continental crust often have continental crust often have dimensions of 5-25 km by 20-100 km. dimensions of 5-25 km by 20-100 km. We must be able to constrain the We must be able to constrain the shapes of these blocks in 3D to shapes of these blocks in 3D to understand rifting tectonics. understand rifting tectonics. Individual Individual blocks cannot typically be resolved blocks cannot typically be resolved using altimetry derived gravity using altimetry derived gravity observations.observations. With the proposed With the proposed resolution increase, they might be.resolution increase, they might be.


Galicia Rifted Margin ISE97 Line 1Galicia Rifted Margin ISE97 Line 1

10

5

6

7

8

9

10 KM

VE~5X

S

Stack, FK Time Migration at 1600 m/s, 1000 ms AGC


Why RCL?Why RCL?

2D seismic reflection methods extend 2D seismic reflection methods extend ground truth outward from a more ground truth outward from a more expensive borehole. Similarly, 3D expensive borehole. Similarly, 3D seismic reflection data and/or altimetry seismic reflection data and/or altimetry derived gravity data can extend that derived gravity data can extend that truth outward from 2D seismic profiles. truth outward from 2D seismic profiles. We will not soon have regional scale 3D We will not soon have regional scale 3D seismic surveys of all the MARGINS seismic surveys of all the MARGINS focus areas, particularly the RCL focus focus areas, particularly the RCL focus areas.areas.


MARGINS is not all there is to studying MARGINS is not all there is to studying margins! Many smaller scale, less multi-margins! Many smaller scale, less multi-disciplinary studies of margins will continue disciplinary studies of margins will continue to happen outside the MARGINS umbrella to happen outside the MARGINS umbrella ((audience says “Amen”audience says “Amen”).).

Presentations by colleagues (including Presentations by colleagues (including those yesterday by Chris Massel and Barry those yesterday by Chris Massel and Barry Eakins) at this meeting describe tectonic Eakins) at this meeting describe tectonic applications of the kind pursued by many applications of the kind pursued by many margins researchers.margins researchers.

Outside the MARGINS Focus areas, Outside the MARGINS Focus areas, investigators depend more heavily on investigators depend more heavily on complementary and readily available data complementary and readily available data sources like altimetry derived gravity and sources like altimetry derived gravity and bathymetry.bathymetry.


Final ThoughtFinal Thought Altimetry derived gravity and bathymetry Altimetry derived gravity and bathymetry

has become part of the fundamental has become part of the fundamental toolset for doing marine geology and toolset for doing marine geology and geophysics. We all use it, for research geophysics. We all use it, for research and for education, without thinking much and for education, without thinking much about it.about it.

There must/should be a mechanism for There must/should be a mechanism for the funding of improved global datasets the funding of improved global datasets that impact so much learning and so that impact so much learning and so many researchers, students, and citizens.many researchers, students, and citizens.

By the way --- Thanks David and Walter, By the way --- Thanks David and Walter, the Navy, NSF, and whoever else I am the Navy, NSF, and whoever else I am leaving out.leaving out.

workshop on global bathymetry for oceanography, geophysics, and climatology24-26 october 2002...

Documents

evolution of margins

margins program

margins studies

margins interests

margins initiative

margins approach

bathymetry data

data quality