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Andre Horbach - One of the best experts on this subject based on the ideXlab platform.

  • stability of the rotation axis in high resolution mantle circulation models weak polar wander despite strong core heating
    Geochemistry Geophysics Geosystems, 2009
    Co-Authors: Katrin Schaber, Hanspeter Bunge, Bernhard S A Schuberth, Rocco Malservisi, Andre Horbach
    Abstract:

    [1] Growing evidence points to a substantial heat flow across the core-mantle boundary (CMB), but the rotational stability of strongly bottom heated mantle flow with prominent upwelling plumes is poorly known. Here we calculate polar motion for the past 100 Myr induced in a new class of isochemical high-resolution mantle circulation models (MCMs) with Earth-like convective vigor and up to 12 TW core heat flux. Our MCMs include internal heating and a simple three-layer viscosity profile associated with the lithosphere (1023 Pa s) and the upper (1021 Pa s) and the lower mantle (1023 Pa s), separated at 100 and 650 km depth, respectively. A published mantle mineralogy model in the pyrolite composition, consistent with our assumption of whole mantle flow, allows us to relate thermal to density variations in a thermodynamically self-consistent way. All models yield modest polar motion on the order of 0.5° Myr−1 or less, in accordance with paleomagnetic data and agreeing with a number of studies that demonstrate the stabilizing effect of the rotational bulge. Although a substantially reduced lower mantle viscosity would increase this rate, the good agreement between MCM and seismic mantle heterogeneity lends independent support for our viscosity profile, as otherwise, slabs in the MCM would rapidly sink to depth levels where they are tomographically not observed. In general, there is good agreement between the long-wavelength geoids predicted from our MCMs and recent satellite derived models of Earth's geoid (correlation coefficient of around 0.4), but noticeable differences at intermediate wavelengths, for example, in the western Pacific and in Africa, suggest the use of gravity data to distinguish between competing Plate Reconstruction models.

Sascha Brune - One of the best experts on this subject based on the ideXlab platform.

  • Oblique rifting: the rule, not the exception
    Solid Earth, 2018
    Co-Authors: Sascha Brune, Simon E Williams, R. Dietmar Müller
    Abstract:

    Abstract. Movements of tectonic Plates often induce oblique deformation at divergent Plate boundaries. This is in striking contrast with traditional conceptual models of rifting and rifted margin formation, which often assume 2-D deformation where the rift velocity is oriented perpendicular to the Plate boundary. Here we quantify the validity of this assumption by analysing the kinematics of major continent-scale rift systems in a global Plate tectonic Reconstruction from the onset of Pangea breakup until the present day. We evaluate rift obliquity by joint examination of relative extension velocity and local rift trend using the script-based Plate Reconstruction software pyGPlates. Our results show that the global mean rift obliquity since 230 Ma amounts to 34° with a standard deviation of 24°, using the convention that the angle of obliquity is spanned by extension direction and rift trend normal. We find that more than  ∼ 70 % of all rift segments exceeded an obliquity of 20° demonstrating that oblique rifting should be considered the rule, not the exception. In many cases, rift obliquity and extension velocity increase during rift evolution (e.g. Australia-Antarctica, Gulf of California, South Atlantic, India-Antarctica), which suggests an underlying geodynamic correlation via obliquity-dependent rift strength. Oblique rifting produces 3-D stress and strain fields that cannot be accounted for in simplified 2-D plane strain analysis. We therefore highlight the importance of 3-D approaches in modelling, surveying, and interpretation of most rift segments on Earth where oblique rifting is the dominant mode of deformation.

  • Oblique rifting: the rule, not the exception
    2018
    Co-Authors: Sascha Brune, Simon E. Willliams, R. Dietmar Müller
    Abstract:

    <p><strong>Abstract.</strong> Movements of tectonic Plates often induce oblique deformation at divergent Plate boundaries. This is in striking contrast with traditional conceptual models of rifting and rifted margin formation, which often assume 2D deformation where the rift velocity is oriented perpendicular to the Plate boundary. Here we quantify the validity of this assumption by analysing the kinematics of major continent-scale rift systems in a global Plate tectonic Reconstruction from the onset of Pangea breakup until present-day. We evaluate rift obliquity by joint examination of relative extension velocity and local rift trend using the script-based Plate Reconstruction software pyGPlates. Our results show that the global mean rift obliquity amounts to 34° with a standard deviation of 24°, using the convention that the angle of obliquity is spanned by extension direction and rift trend normal. We find that more than ~ 70 % of all rift segments exceeded an obliquity of 20° demonstrating that oblique rifting should be considered the rule, not the exception. In many cases, rift obliquity and extension velocity increase during rift evolution (e.g. Australia-Antarctica, Gulf of California, South Atlantic, India-Antarctica), which suggests an underlying geodynamic correlation via obliquity-dependent rift strength. Oblique rifting produces 3D stress and strain fields that cannot be accounted for in simplified 2D plane strain analysis. We therefore highlight the importance of 3D approaches in modelling, surveying, and interpretation of most rift segments on Earth where oblique rifting is the dominant mode of deformation.</p>

  • Rift migration explains continental margin asymmetry and crustal hyper-extension
    Nature communications, 2014
    Co-Authors: Sascha Brune, Christian Heine, M. Perez-gussinye, Stephan V. Sobolev
    Abstract:

    When continents break apart, continental crust and lithosphere are thinned until break-up is achieved and an oceanic basin is formed. The most remarkable and least understood structures associated with this process are up to 200 km wide areas of hyper-extended continental crust, which are partitioned between conjugate margins with pronounced asymmetry. Here we show, using high-resolution thermo-mechanical modelling, that hyper-extended crust and margin asymmetry are produced by steady state rift migration. We demonstrate that rift migration is accomplished by sequential, oceanward-younging, upper crustal faults, and is balanced through lower crustal flow. Constraining our model with a new South Atlantic Plate Reconstruction, we demonstrate that larger extension velocities may account for southward increasing width and asymmetry of these conjugate magma-poor margins. Our model challenges conventional ideas of rifted margin evolution, as it implies that during rift migration large amounts of material are transferred from one side of the rift zone to the other.

  • Rift migration explains continental margin asymmetry and crustal hyper-extension
    Nature Communications, 2014
    Co-Authors: Sascha Brune, Christian Heine, M. Perez-gussinye, Stephan V. Sobolev
    Abstract:

    During continental rifting, various stages and structures are observed, the least understood being hyper-extended continental crust at magma-poor margins. Here, the authors use finite-element thermomechanical models to investigate the mechanism causing observed margin asymmetry and crustal hyper-extension. When continents break apart, continental crust and lithosphere are thinned until break-up is achieved and an oceanic basin is formed. The most remarkable and least understood structures associated with this process are up to 200 km wide areas of hyper-extended continental crust, which are partitioned between conjugate margins with pronounced asymmetry. Here we show, using high-resolution thermo-mechanical modelling, that hyper-extended crust and margin asymmetry are produced by steady state rift migration. We demonstrate that rift migration is accomplished by sequential, oceanward-younging, upper crustal faults, and is balanced through lower crustal flow. Constraining our model with a new South Atlantic Plate Reconstruction, we demonstrate that larger extension velocities may account for southward increasing width and asymmetry of these conjugate magma-poor margins. Our model challenges conventional ideas of rifted margin evolution, as it implies that during rift migration large amounts of material are transferred from one side of the rift zone to the other.

R. Dietmar Müller - One of the best experts on this subject based on the ideXlab platform.

  • Oblique rifting: the rule, not the exception
    Solid Earth, 2018
    Co-Authors: Sascha Brune, Simon E Williams, R. Dietmar Müller
    Abstract:

    Abstract. Movements of tectonic Plates often induce oblique deformation at divergent Plate boundaries. This is in striking contrast with traditional conceptual models of rifting and rifted margin formation, which often assume 2-D deformation where the rift velocity is oriented perpendicular to the Plate boundary. Here we quantify the validity of this assumption by analysing the kinematics of major continent-scale rift systems in a global Plate tectonic Reconstruction from the onset of Pangea breakup until the present day. We evaluate rift obliquity by joint examination of relative extension velocity and local rift trend using the script-based Plate Reconstruction software pyGPlates. Our results show that the global mean rift obliquity since 230 Ma amounts to 34° with a standard deviation of 24°, using the convention that the angle of obliquity is spanned by extension direction and rift trend normal. We find that more than  ∼ 70 % of all rift segments exceeded an obliquity of 20° demonstrating that oblique rifting should be considered the rule, not the exception. In many cases, rift obliquity and extension velocity increase during rift evolution (e.g. Australia-Antarctica, Gulf of California, South Atlantic, India-Antarctica), which suggests an underlying geodynamic correlation via obliquity-dependent rift strength. Oblique rifting produces 3-D stress and strain fields that cannot be accounted for in simplified 2-D plane strain analysis. We therefore highlight the importance of 3-D approaches in modelling, surveying, and interpretation of most rift segments on Earth where oblique rifting is the dominant mode of deformation.

  • Oblique rifting: the rule, not the exception
    2018
    Co-Authors: Sascha Brune, Simon E. Willliams, R. Dietmar Müller
    Abstract:

    <p><strong>Abstract.</strong> Movements of tectonic Plates often induce oblique deformation at divergent Plate boundaries. This is in striking contrast with traditional conceptual models of rifting and rifted margin formation, which often assume 2D deformation where the rift velocity is oriented perpendicular to the Plate boundary. Here we quantify the validity of this assumption by analysing the kinematics of major continent-scale rift systems in a global Plate tectonic Reconstruction from the onset of Pangea breakup until present-day. We evaluate rift obliquity by joint examination of relative extension velocity and local rift trend using the script-based Plate Reconstruction software pyGPlates. Our results show that the global mean rift obliquity amounts to 34° with a standard deviation of 24°, using the convention that the angle of obliquity is spanned by extension direction and rift trend normal. We find that more than ~ 70 % of all rift segments exceeded an obliquity of 20° demonstrating that oblique rifting should be considered the rule, not the exception. In many cases, rift obliquity and extension velocity increase during rift evolution (e.g. Australia-Antarctica, Gulf of California, South Atlantic, India-Antarctica), which suggests an underlying geodynamic correlation via obliquity-dependent rift strength. Oblique rifting produces 3D stress and strain fields that cannot be accounted for in simplified 2D plane strain analysis. We therefore highlight the importance of 3D approaches in modelling, surveying, and interpretation of most rift segments on Earth where oblique rifting is the dominant mode of deformation.</p>

  • Global tectonic Reconstructions with continuously deforming and evolving rigid Plates
    Computers & Geosciences, 2018
    Co-Authors: Michael Gurnis, Nicolas Flament, Ting Yang, J. Cannon, Mark Turner, Simon Williams, R. Dietmar Müller
    Abstract:

    Traditional Plate Reconstruction methodologies do not allow for Plate deformation to be considered. Here we present software to construct and visualize global tectonic Reconstructions with deforming Plates within the context of rigid Plates. Both deforming and rigid Plates are defined by continuously evolving polygons. The deforming regions are tessellated with triangular meshes such that either strain rate or cumulative strain can be followed. The finite strain history, crustal thickness and stretching factor of points within the deformation zones are tracked as Lagrangian points. Integrating these tools within the interactive platform GPlates enables specialized users to build and refine deforming Plate models and integrate them with other models in time and space. We demonstrate the integrated platform with regional Reconstructions of Cenozoic western North America, the Mesozoic South American Atlantic margin, and Cenozoic southeast Asia, embedded within global Reconstructions, using different data and Reconstruction strategies.

  • Formation and evolution of the Chain-Kairali Escarpment and the Vishnu Fracture Zone in the Western Indian Ocean
    Journal of Asian Earth Sciences, 2018
    Co-Authors: M. Shuhail, R. Dietmar Müller, V. Yatheesh, G.c. Bhattacharya, K. A. Kamesh Raju, Kotha Mahender
    Abstract:

    Abstract Published models for the Plate tectonic evolution of the Western Indian Ocean suggest that the Southern Mascarene Basin opened by oceanic crustal accretion between the continental margins of southwestern India and southeastern Madagascar. However, with the cessation of the Mascarene Basin spreading centre followed by a ridge jump resulting in the opening of the Carlsberg Ridge, almost all the traces of India-Madagascar divergence were carved away from the Indian Plate and attached to the African Plate. According to some recent studies, the Chain-Kairali Escarpment, a prominent feature on the southwestern continental margin of India, is possibly the only trace of India-Madagascar divergence that remained on the Indian Plate. But the exact conjugate correspondence of this feature on the Madagascar side is uncertain. Published Plate tectonic Reconstructions imply that the Vishnu Fracture Zone on the Indian side and the Mauritius Fracture Zone on the Madagascar side are aligned at chron C22ny (∼49.04 Ma). Based on the near collinearity of gravity anomaly trends, the Chain-Kairali Escarpment appears to be the landward extension of the Vishnu FZ. However, at chron C34ny (∼83.0 Ma), the Chain-Kairali Escarpment was in close proximity to the incipient Mahanoro Fracture Zone. In this study we investigate this incompatibility, using an up-to-date compilation of the tectonic elements from the conjugate regions of India and Madagascar and the latest available rotation parameters that describe India-Madagascar separation through a direct India-Seychelles-Madagascar Plate circuit. Our revised Plate Reconstruction model suggests that the Chain-Kairali Escarpment was formed due to the strike-slip motion between the southeast coast of Madagascar and the then southwest coast of India during the initial stages of India-Madagascar breakup. The migration of the Chain-Kairali Escarpment from the proximity of the Mahanoro FZ and aligning with the Vishnu FZ was the result of several successive events. The first among those events was asymmetric crustal accretion in the Mascarene Basin due to ridge propagation, between chrons C34ny (83.0 Ma) to C33ny (∼73.62 Ma). The Chain-Kairali Escarpment and associated crustal weak zones offshore India appear to have facilitated subsequent initiation of the Mauritius FZ and its conjugate Vishnu FZ during a Plate reorganization at about chron C33ny (∼73.62 Ma). The cessation of spreading in the Mascarene Basin and development of full extent of the Carlsberg Ridge, shortly after chron C27ny (60.92 Ma), resulted in the initiation of a long transform fault, coinciding with the Vishnu FZ, which connected the Carlsberg Ridge with the spreading centre of the Madagascar Basin. Therefore, the Vishnu FZ and the Chain-Kairali Escarpment are two independent features created during different episodes of evolution of the Western Indian Ocean and the Chain-Kairali Escarpment is not a landward extension of the Vishnu FZ.

Katrin Schaber - One of the best experts on this subject based on the ideXlab platform.

  • stability of the rotation axis in high resolution mantle circulation models weak polar wander despite strong core heating
    Geochemistry Geophysics Geosystems, 2009
    Co-Authors: Katrin Schaber, Hanspeter Bunge, Bernhard S A Schuberth, Rocco Malservisi, Andre Horbach
    Abstract:

    [1] Growing evidence points to a substantial heat flow across the core-mantle boundary (CMB), but the rotational stability of strongly bottom heated mantle flow with prominent upwelling plumes is poorly known. Here we calculate polar motion for the past 100 Myr induced in a new class of isochemical high-resolution mantle circulation models (MCMs) with Earth-like convective vigor and up to 12 TW core heat flux. Our MCMs include internal heating and a simple three-layer viscosity profile associated with the lithosphere (1023 Pa s) and the upper (1021 Pa s) and the lower mantle (1023 Pa s), separated at 100 and 650 km depth, respectively. A published mantle mineralogy model in the pyrolite composition, consistent with our assumption of whole mantle flow, allows us to relate thermal to density variations in a thermodynamically self-consistent way. All models yield modest polar motion on the order of 0.5° Myr−1 or less, in accordance with paleomagnetic data and agreeing with a number of studies that demonstrate the stabilizing effect of the rotational bulge. Although a substantially reduced lower mantle viscosity would increase this rate, the good agreement between MCM and seismic mantle heterogeneity lends independent support for our viscosity profile, as otherwise, slabs in the MCM would rapidly sink to depth levels where they are tomographically not observed. In general, there is good agreement between the long-wavelength geoids predicted from our MCMs and recent satellite derived models of Earth's geoid (correlation coefficient of around 0.4), but noticeable differences at intermediate wavelengths, for example, in the western Pacific and in Africa, suggest the use of gravity data to distinguish between competing Plate Reconstruction models.

Stephan V. Sobolev - One of the best experts on this subject based on the ideXlab platform.

  • Rift migration explains continental margin asymmetry and crustal hyper-extension
    Nature communications, 2014
    Co-Authors: Sascha Brune, Christian Heine, M. Perez-gussinye, Stephan V. Sobolev
    Abstract:

    When continents break apart, continental crust and lithosphere are thinned until break-up is achieved and an oceanic basin is formed. The most remarkable and least understood structures associated with this process are up to 200 km wide areas of hyper-extended continental crust, which are partitioned between conjugate margins with pronounced asymmetry. Here we show, using high-resolution thermo-mechanical modelling, that hyper-extended crust and margin asymmetry are produced by steady state rift migration. We demonstrate that rift migration is accomplished by sequential, oceanward-younging, upper crustal faults, and is balanced through lower crustal flow. Constraining our model with a new South Atlantic Plate Reconstruction, we demonstrate that larger extension velocities may account for southward increasing width and asymmetry of these conjugate magma-poor margins. Our model challenges conventional ideas of rifted margin evolution, as it implies that during rift migration large amounts of material are transferred from one side of the rift zone to the other.

  • Rift migration explains continental margin asymmetry and crustal hyper-extension
    Nature Communications, 2014
    Co-Authors: Sascha Brune, Christian Heine, M. Perez-gussinye, Stephan V. Sobolev
    Abstract:

    During continental rifting, various stages and structures are observed, the least understood being hyper-extended continental crust at magma-poor margins. Here, the authors use finite-element thermomechanical models to investigate the mechanism causing observed margin asymmetry and crustal hyper-extension. When continents break apart, continental crust and lithosphere are thinned until break-up is achieved and an oceanic basin is formed. The most remarkable and least understood structures associated with this process are up to 200 km wide areas of hyper-extended continental crust, which are partitioned between conjugate margins with pronounced asymmetry. Here we show, using high-resolution thermo-mechanical modelling, that hyper-extended crust and margin asymmetry are produced by steady state rift migration. We demonstrate that rift migration is accomplished by sequential, oceanward-younging, upper crustal faults, and is balanced through lower crustal flow. Constraining our model with a new South Atlantic Plate Reconstruction, we demonstrate that larger extension velocities may account for southward increasing width and asymmetry of these conjugate magma-poor margins. Our model challenges conventional ideas of rifted margin evolution, as it implies that during rift migration large amounts of material are transferred from one side of the rift zone to the other.