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Philippe Vernant - One of the best experts on this subject based on the ideXlab platform.

  • Present-day uplift of the western Alps.
    Scientific Reports, 2016
    Co-Authors: Jean-mathieu Nocquet, Andrea Walpersdorf, Thi Phuong Anh Tran, Nicole Lenotre, Philippe Vernant, Marc Cushing, François Jouanne, Frédéric Masson, Stéphane Baize
    Abstract:

    Collisional mountain belts grow as a consequence of continental plate convergence and eventually disappear under the combined effects of gravitational collapse and erosion. Using a decade of GPS data, we show that the western Alps are currently characterized by zero horizontal velocity boundary conditions, offering the opportunity to investigate orogen evolution at the time of cessation of plate convergence. We find no significant horizontal motion within the belt, but GPS and levelling measurements independently show a regional pattern of uplift reaching ~2.5 mm/yr in the northwestern Alps. Unless a low viscosity Crustal Root under the northwestern Alps locally enhances the vertical response to surface unloading, the summed effects of isostatic responses to erosion and glaciation explain at most 60% of the observed uplift rates. Rock-uplift rates corrected from transient glacial isostatic adjustment contributions likely exceed erosion rates in the northwestern Alps. In the absence of active convergence, the observed surface uplift must result from deep-seated processes.

  • ice cap melting and low viscosity Crustal Root explain the narrow geodetic uplift of the western alps
    Geophysical Research Letters, 2016
    Co-Authors: Jean Chéry, Manon Genti, Philippe Vernant
    Abstract:

    More than 10 years of geodetic measurements demonstrate an uplift rate of 1–3 mm/yr of the high topography region of the Western Alps. By contrast, no significant horizontal motion has been detected. Two uplift mechanisms have been proposed: (1) the isostatic response to denudation responsible for only a fraction of the observed uplift and (2) the rebound induced by the Wurmian ice cap melting which predicts a broader uplifting region than the one evidenced by geodetic observations. Using a numerical model to fit the geodetic data, we show that a Crustal viscosity contrast between the foreland and the central part of the Alps, the latter being weaker with a viscosity of 1021 Pa s, is needed. The vertical rates are enhanced if the strong uppermost mantle beneath the Moho is interrupted across the Alps, therefore allowing a weak vertical rheological anomaly over the entire lithosphere.

  • Ice cap melting and low‐viscosity Crustal Root explain the narrow geodetic uplift of the Western Alps
    Geophysical Research Letters, 2016
    Co-Authors: Jean Chéry, Manon Genti, Philippe Vernant
    Abstract:

    More than 10 years of geodetic measurements demonstrate an uplift rate of 1–3 mm/yr of the high topography region of the Western Alps. By contrast, no significant horizontal motion has been detected. Two uplift mechanisms have been proposed: (1) the isostatic response to denudation responsible for only a fraction of the observed uplift and (2) the rebound induced by the Wurmian ice cap melting which predicts a broader uplifting region than the one evidenced by geodetic observations. Using a numerical model to fit the geodetic data, we show that a Crustal viscosity contrast between the foreland and the central part of the Alps, the latter being weaker with a viscosity of 1021 Pa s, is needed. The vertical rates are enhanced if the strong uppermost mantle beneath the Moho is interrupted across the Alps, therefore allowing a weak vertical rheological anomaly over the entire lithosphere.

Bertram Schott - One of the best experts on this subject based on the ideXlab platform.

  • continental collision and the dynamic and thermal evolution of the variscan orogenic Crustal Root numerical models
    Journal of Geodynamics, 2001
    Co-Authors: J. Arnold, Wolfgang R. Jacoby, Harro Schmeling, Bertram Schott
    Abstract:

    Abstract Orogeny is modelled numerically by treating continental collision within full convection solutions, in order to better understand some aspects of the Variscan structures and processes. Three different approaches are taken: (1) collision where one ‘continental plate’ is ‘pushed’ against another across a zone of weakness; (2) gravitational instability of a lithospheric mantle Root leading to delamination, slab break-off and Crustal Root reduction; (3) melting in the lower part of a Crustal orogenic Root. The first approach demonstrates that thick (but in the models: cool) Roots can accumulate, in which upper Crustal rocks are carried to great depth and mantle material may be carried towards upper Crustal levels. The second approach shows that lithospheric Root break-off can lead to rapid Crustal uplift and thinning of the lower crust if its viscosity is sufficiently low. The third approach suggests that internal heating in a thickened crust may lead to melting and granit formation, however, only after a long geological time (in the order of 100 Ma), while delamination and asthenospheric heat advection may achieve this in shorter time periods (in the order of 10 Ma). The different models tested all demonstrate that Crustal Root formation and destruction by uplift and exhumation can be achieved in geologically short time periods (1–10 Ma).

  • Continental collision and the dynamic and thermal evolution of the Variscan orogenic Crustal Root — numerical models
    Journal of Geodynamics, 2001
    Co-Authors: J. Arnold, Wolfgang R. Jacoby, Harro Schmeling, Bertram Schott
    Abstract:

    Abstract Orogeny is modelled numerically by treating continental collision within full convection solutions, in order to better understand some aspects of the Variscan structures and processes. Three different approaches are taken: (1) collision where one ‘continental plate’ is ‘pushed’ against another across a zone of weakness; (2) gravitational instability of a lithospheric mantle Root leading to delamination, slab break-off and Crustal Root reduction; (3) melting in the lower part of a Crustal orogenic Root. The first approach demonstrates that thick (but in the models: cool) Roots can accumulate, in which upper Crustal rocks are carried to great depth and mantle material may be carried towards upper Crustal levels. The second approach shows that lithospheric Root break-off can lead to rapid Crustal uplift and thinning of the lower crust if its viscosity is sufficiently low. The third approach suggests that internal heating in a thickened crust may lead to melting and granit formation, however, only after a long geological time (in the order of 100 Ma), while delamination and asthenospheric heat advection may achieve this in shorter time periods (in the order of 10 Ma). The different models tested all demonstrate that Crustal Root formation and destruction by uplift and exhumation can be achieved in geologically short time periods (1–10 Ma).

Henry N. Pollack - One of the best experts on this subject based on the ideXlab platform.

  • A gravity model for the lithosphere in western Kenya and northeastern Tanzania
    Tectonophysics, 1992
    Co-Authors: Andrew A. Nyblade, Henry N. Pollack
    Abstract:

    We present a new gravity model for the lithosphere beneath the Kenya Rift Valley, the Mozambique Belt, and the Tanzania Craton in western Kenya and northeaatem Tanzania. The Kenya Rii lies within the eastern branch of the extensive Cetnwoie East African Rift System and has developed almost entirely in the Pan-African M~b~que Belt about 50 to 150 km east of the exposed margin of the Archean Tanzania Craton. The gravity field over western Kenya and northeastern Tanzania is characterized by a long-wavelength Bnuguer anomaly. We propose that this anomnly has two components: (1) a “rift” signature, deriving from a shalknv rift basin, a lower Crustal intrusion and a low-density gone in the mantle lithosphere 1ocallzed beneath the rift axis, and (2) a “suture” signature, arising from a Crustal Root along the boundary between the Moaambiqne Belt and Tanaania Craton and higher density crust in the mobile belt above part of the Crustal Root. Two lines of reasoning support our inte~re~tion: (1) Recent geologlcal studies of the M~bique Belt in Kenya and Tanzania suggest that it is a ~ntinent-~n~nent collision aone, and continent-axrtinent collision zones worldwide commonly exhibit a characteristic gravity anomaly. (2) The long-wavelength Bouguer anomaly has at least two minii one over the craton-mobile belt boundary, and one or more over the rift valley. Corroborative evidence for our interpretation of the gravity field is provided by recent seismic investigations.

  • A gravity model for the lithosphere in western Kenya and northeastern Tanzania
    Tectonophysics, 1992
    Co-Authors: Andrew A. Nyblade, Henry N. Pollack
    Abstract:

    We present a new gravity model for the lithosphere beneath the Kenya Rift Valley, the Mozambique Belt, and the Tanzania Craton in western Kenya and northeastern Tanzania. The Kenya Rift lies within the eastern branch of the extensive Cenozoic East African Rift System and has developed almost entirely in the Pan-African Mozambique Belt about 50 to 150 km east of the exposed margin of the Archean Tanzania Craton. The gravity field over western Kenya and northeastern Tanzania is characterized by a long-wavelength Bouguer anomaly. We propose that this anomaly has two components: 1. (1) a "rift" signature, deriving from a shallow rift basin, a lower Crustal intrusion and a low-density zone in the mantle lithosphere localized beneath the rift axis2. (2) a "suture" signature, arising from a Crustal Root along the boundary between the Mozambique Belt and Tanzania Craton and higher density crust in the mobile belt above part of the Crustal Root. Two lines of reasoning support our interpretation: 1. (1) Recent geological studies of the Mozambique Belt in Kenya and Tanzania suggest that it is a continent-continent collision zone, and continent-continent collision zones worldwide commonly exhibit a characteristic gravity anomaly.2. (2) The long-wavelength Bouguer anomaly has at least two minima, one over the craton-mobile belt boundary, and one or more over the rift valley. Corroborative evidence for our interpretation of the gravity field is provided by recent seismic investigations

J. Arnold - One of the best experts on this subject based on the ideXlab platform.

  • continental collision and the dynamic and thermal evolution of the variscan orogenic Crustal Root numerical models
    Journal of Geodynamics, 2001
    Co-Authors: J. Arnold, Wolfgang R. Jacoby, Harro Schmeling, Bertram Schott
    Abstract:

    Abstract Orogeny is modelled numerically by treating continental collision within full convection solutions, in order to better understand some aspects of the Variscan structures and processes. Three different approaches are taken: (1) collision where one ‘continental plate’ is ‘pushed’ against another across a zone of weakness; (2) gravitational instability of a lithospheric mantle Root leading to delamination, slab break-off and Crustal Root reduction; (3) melting in the lower part of a Crustal orogenic Root. The first approach demonstrates that thick (but in the models: cool) Roots can accumulate, in which upper Crustal rocks are carried to great depth and mantle material may be carried towards upper Crustal levels. The second approach shows that lithospheric Root break-off can lead to rapid Crustal uplift and thinning of the lower crust if its viscosity is sufficiently low. The third approach suggests that internal heating in a thickened crust may lead to melting and granit formation, however, only after a long geological time (in the order of 100 Ma), while delamination and asthenospheric heat advection may achieve this in shorter time periods (in the order of 10 Ma). The different models tested all demonstrate that Crustal Root formation and destruction by uplift and exhumation can be achieved in geologically short time periods (1–10 Ma).

  • Continental collision and the dynamic and thermal evolution of the Variscan orogenic Crustal Root — numerical models
    Journal of Geodynamics, 2001
    Co-Authors: J. Arnold, Wolfgang R. Jacoby, Harro Schmeling, Bertram Schott
    Abstract:

    Abstract Orogeny is modelled numerically by treating continental collision within full convection solutions, in order to better understand some aspects of the Variscan structures and processes. Three different approaches are taken: (1) collision where one ‘continental plate’ is ‘pushed’ against another across a zone of weakness; (2) gravitational instability of a lithospheric mantle Root leading to delamination, slab break-off and Crustal Root reduction; (3) melting in the lower part of a Crustal orogenic Root. The first approach demonstrates that thick (but in the models: cool) Roots can accumulate, in which upper Crustal rocks are carried to great depth and mantle material may be carried towards upper Crustal levels. The second approach shows that lithospheric Root break-off can lead to rapid Crustal uplift and thinning of the lower crust if its viscosity is sufficiently low. The third approach suggests that internal heating in a thickened crust may lead to melting and granit formation, however, only after a long geological time (in the order of 100 Ma), while delamination and asthenospheric heat advection may achieve this in shorter time periods (in the order of 10 Ma). The different models tested all demonstrate that Crustal Root formation and destruction by uplift and exhumation can be achieved in geologically short time periods (1–10 Ma).

Andrew A. Nyblade - One of the best experts on this subject based on the ideXlab platform.

  • A gravity model for the lithosphere in western Kenya and northeastern Tanzania
    Tectonophysics, 1992
    Co-Authors: Andrew A. Nyblade, Henry N. Pollack
    Abstract:

    We present a new gravity model for the lithosphere beneath the Kenya Rift Valley, the Mozambique Belt, and the Tanzania Craton in western Kenya and northeaatem Tanzania. The Kenya Rii lies within the eastern branch of the extensive Cetnwoie East African Rift System and has developed almost entirely in the Pan-African M~b~que Belt about 50 to 150 km east of the exposed margin of the Archean Tanzania Craton. The gravity field over western Kenya and northeastern Tanzania is characterized by a long-wavelength Bnuguer anomaly. We propose that this anomnly has two components: (1) a “rift” signature, deriving from a shalknv rift basin, a lower Crustal intrusion and a low-density gone in the mantle lithosphere 1ocallzed beneath the rift axis, and (2) a “suture” signature, arising from a Crustal Root along the boundary between the Moaambiqne Belt and Tanaania Craton and higher density crust in the mobile belt above part of the Crustal Root. Two lines of reasoning support our inte~re~tion: (1) Recent geologlcal studies of the M~bique Belt in Kenya and Tanzania suggest that it is a ~ntinent-~n~nent collision aone, and continent-axrtinent collision zones worldwide commonly exhibit a characteristic gravity anomaly. (2) The long-wavelength Bouguer anomaly has at least two minii one over the craton-mobile belt boundary, and one or more over the rift valley. Corroborative evidence for our interpretation of the gravity field is provided by recent seismic investigations.

  • A gravity model for the lithosphere in western Kenya and northeastern Tanzania
    Tectonophysics, 1992
    Co-Authors: Andrew A. Nyblade, Henry N. Pollack
    Abstract:

    We present a new gravity model for the lithosphere beneath the Kenya Rift Valley, the Mozambique Belt, and the Tanzania Craton in western Kenya and northeastern Tanzania. The Kenya Rift lies within the eastern branch of the extensive Cenozoic East African Rift System and has developed almost entirely in the Pan-African Mozambique Belt about 50 to 150 km east of the exposed margin of the Archean Tanzania Craton. The gravity field over western Kenya and northeastern Tanzania is characterized by a long-wavelength Bouguer anomaly. We propose that this anomaly has two components: 1. (1) a "rift" signature, deriving from a shallow rift basin, a lower Crustal intrusion and a low-density zone in the mantle lithosphere localized beneath the rift axis2. (2) a "suture" signature, arising from a Crustal Root along the boundary between the Mozambique Belt and Tanzania Craton and higher density crust in the mobile belt above part of the Crustal Root. Two lines of reasoning support our interpretation: 1. (1) Recent geological studies of the Mozambique Belt in Kenya and Tanzania suggest that it is a continent-continent collision zone, and continent-continent collision zones worldwide commonly exhibit a characteristic gravity anomaly.2. (2) The long-wavelength Bouguer anomaly has at least two minima, one over the craton-mobile belt boundary, and one or more over the rift valley. Corroborative evidence for our interpretation of the gravity field is provided by recent seismic investigations