During gravitational collapse, the root of the orogen
can be exhumed at the surface in metamorphic core complexes. These crustal scale structures are domes of highgrade rocks located in the hanging wall of low-angle normal fault systems or detachments (Whitney et al., 2013).
The erosion products of the exhuming hanging wall are
deposited in supradetachment basins. The formation of
metamorphic core complexes is controlled by the rheological layering of the lithosphere at the onset of collapse
(Buck, 1991). However, the exhumation of these domeshaped structures below low-angle normal faults has long
been considered as mechanically paradoxical. Thermomechanical modeling and field observations have shown that
warm geotherms, intrusions (Tirel et al., 2008), partial
melting (Rey et al., 2009), complex crustal layering
inherited from the collision (Huet et al., 2011), and metamorphic reactions (Collettini and Holdsworth, 2004;
Hürzeler and Abart, 2008; Grasemann and Tschegg,
2012) create the conditions for strain localization in
low-angle normal faults and mechanically interacting
high-angle normal faults which rotate to lower angles during ongoing extension. After gravitational collapse, continental crust of normal thickness and thermal regime is
produced. Further extension then leads to continental
rifting and the onset of a new orogenic cycle.
Outlook and conclusions
Much advance has been made in recent years in the understanding of the dynamics of orogenic belts in response to
the large-scale motion of the lithospheric plates and
numerous ideas, many of which developed from studies
on the collision between India and Asia have led to
a better understanding of the thermomechanical evolution
of orogens (for a comprehensive overview see Stüwe,
2007; Turcotte and Schubert, 2014). Large, global geophysical datasets, including topography, gravity, geoid,
and magnetic anomaly, together with new high-resolution
geological datasets constraining the rheology of the lithosphere and the rates of geodynamic processes, increased
our knowledge about the evolution and structure of
orogens (Magni et al., 2013). Numerical thermomechanical models have demonstrated that the dynamics of
orogens is strongly controlled by the temperaturedependent strength distribution within the lithosphere
and the efficiency of erosion. Indeed, the recognition of
a significant linkage of deep Earth dynamic processes with
surface and/or near-surface geological processes is one of
the important developments in Earth sciences over the past
decade (Braun, 2010, Cloetingh and Willet, 2013).
Recently, it has been suggested that mantle dynamics
has a major influence on building mountains. Two orogenic end-members have been distinguished, depending
on the forces controlling the formation of the orogen
(Faccenna et al., 2013). Slab pull dynamics is associated
with slabs subducting in convective upper mantle, trench
rollback, and the formation of mountains with moderate
crustal thickness (e.g., the Mediterranean). Slab suction
is associated with slabs penetrating through the phase transitions around 660 km, leading to the formation of mountains with thick crustal columns (e.g., the Himalayas).
In spite of this rapid increase of our knowledge level
about orogeny, the effects of three-dimensionality in orogenic systems and their forming processes are still poorly
understood. Recent three-dimensional mechanical models
of folding (Schmalholz, 2008; Schmid et al., 2008a),
faulting (Walsh et al., 2001; Imber et al., 2004; Seyferth
and Henk, 2004; Soliva et al, 2008; Le Pourhiet et al., in
review), rifting (Allken et al., 2012), crustal wedges
(Braun and Yamato, 2010), metamorphic core complexes
(Le Pourhiet et al., 2012), and mid-ocean ridges (Gerya,
2012) demonstrated the urgent need to use high-resolution
three-dimensional numerical models in order to further
develop our understanding of geodynamic processes in
orogens.
Bibliography
Agard, P., Omrani, J., Jolivet, L., and Mouthereau, F., 2005. Convergence history across Zagros (Iran): constraints from collisional and earlier deformation. International Journal of Earth
Sciences, 94, 401–419.
Allen, P. A., and Allen, J. R., 2005. Basin Analysis: Principles and
Applications, 2nd edn. Oxford: Wiley-Blackwell.
Allken, V., Huismans, R. S., and Thieulot, C., 2012. Factors controlling the mode of rift interaction in brittle-ductile coupled systems: a 3D numerical study. Geochemistry, Geophysics,
Geosystems, 13, Q05010, doi:10.1029/2012gc004077.
Anders, B., Reischmann, T., Poller, U., and Kostopoulos, D., 2005.
Age and origin of granitic rocks of the eastern Vardar Zone,
Greece: new constraints on the evolution of the Internal
Hellenides. Journal of the Geological Society of London, 162,
857–870.
Avouac, J.-P., and Burov, E. B., 1996. Erosion as a driving mechanism of intracontinental mountain growth. Journal of Geophysical Research, 110, 17747–17769.
Beaumont, C., Ellis, S., Hamilton, J., and Fullsack, P., 1996.
Mechanical model for subduction-collision tectonics of Alpinetype compressional orogens. Geology, 24, 675–678.
Beaumont, C., Jamieson, R. A., Nguyen, M. H., and Lee, B., 2001.
Himalayan tectonics explained by extrusion of a low-viscosity
crustal channel coupled to focused surface denudation. Nature,
414, 738.
Beaumont, C., Jamieson, R. A., Nguyen, M. H., and Medvedev, S.,
2004. Crustal channel flows: 1. Numerical models with applications to the tectonics of the Himalayan-Tibetan orogen. Journal
of Geophysical Research, 109, B06406, doi:10.1029/
2003JB002809.
Becker, J. J., Sandwell, D. T., Smith, W. H. F., Braud, J., Binder, B.,
Depner, J., Fabre, D., Factor, J., Ingalls, S., Kim, S.-H., Ladner,
R., Marks, K., Nelson, S., Pharaoh, A., Trimmer, R., Von Rosenberg, J., Wallace, G., and Weatherall, P., 2009. Global bathymetry and elevation data at 30 arc seconds resolution:
SRTM30_PLUS. Marine Geodesy, 32(4), 355–371.
Braun, J., 2010. The many surface expressions of mantle dynamics.
Nature Geoscience, 3, 825–833.
Braun, J., and Yamato, P., 2010. Structural evolution of a threedimensional, finite-width crustal wedge. Tectonophysics, 484,
181–192.
Buck, W. R., 1991. Modes of continental lithospheric extension.
Journal of Geophysical Research, 96, 20,161–120,178.
OROGENY
607
can be exhumed at the surface in metamorphic core complexes. These crustal scale structures are domes of highgrade rocks located in the hanging wall of low-angle normal fault systems or detachments (Whitney et al., 2013).
The erosion products of the exhuming hanging wall are
deposited in supradetachment basins. The formation of
metamorphic core complexes is controlled by the rheological layering of the lithosphere at the onset of collapse
(Buck, 1991). However, the exhumation of these domeshaped structures below low-angle normal faults has long
been considered as mechanically paradoxical. Thermomechanical modeling and field observations have shown that
warm geotherms, intrusions (Tirel et al., 2008), partial
melting (Rey et al., 2009), complex crustal layering
inherited from the collision (Huet et al., 2011), and metamorphic reactions (Collettini and Holdsworth, 2004;
Hürzeler and Abart, 2008; Grasemann and Tschegg,
2012) create the conditions for strain localization in
low-angle normal faults and mechanically interacting
high-angle normal faults which rotate to lower angles during ongoing extension. After gravitational collapse, continental crust of normal thickness and thermal regime is
produced. Further extension then leads to continental
rifting and the onset of a new orogenic cycle.
Outlook and conclusions
Much advance has been made in recent years in the understanding of the dynamics of orogenic belts in response to
the large-scale motion of the lithospheric plates and
numerous ideas, many of which developed from studies
on the collision between India and Asia have led to
a better understanding of the thermomechanical evolution
of orogens (for a comprehensive overview see Stüwe,
2007; Turcotte and Schubert, 2014). Large, global geophysical datasets, including topography, gravity, geoid,
and magnetic anomaly, together with new high-resolution
geological datasets constraining the rheology of the lithosphere and the rates of geodynamic processes, increased
our knowledge about the evolution and structure of
orogens (Magni et al., 2013). Numerical thermomechanical models have demonstrated that the dynamics of
orogens is strongly controlled by the temperaturedependent strength distribution within the lithosphere
and the efficiency of erosion. Indeed, the recognition of
a significant linkage of deep Earth dynamic processes with
surface and/or near-surface geological processes is one of
the important developments in Earth sciences over the past
decade (Braun, 2010, Cloetingh and Willet, 2013).
Recently, it has been suggested that mantle dynamics
has a major influence on building mountains. Two orogenic end-members have been distinguished, depending
on the forces controlling the formation of the orogen
(Faccenna et al., 2013). Slab pull dynamics is associated
with slabs subducting in convective upper mantle, trench
rollback, and the formation of mountains with moderate
crustal thickness (e.g., the Mediterranean). Slab suction
is associated with slabs penetrating through the phase transitions around 660 km, leading to the formation of mountains with thick crustal columns (e.g., the Himalayas).
In spite of this rapid increase of our knowledge level
about orogeny, the effects of three-dimensionality in orogenic systems and their forming processes are still poorly
understood. Recent three-dimensional mechanical models
of folding (Schmalholz, 2008; Schmid et al., 2008a),
faulting (Walsh et al., 2001; Imber et al., 2004; Seyferth
and Henk, 2004; Soliva et al, 2008; Le Pourhiet et al., in
review), rifting (Allken et al., 2012), crustal wedges
(Braun and Yamato, 2010), metamorphic core complexes
(Le Pourhiet et al., 2012), and mid-ocean ridges (Gerya,
2012) demonstrated the urgent need to use high-resolution
three-dimensional numerical models in order to further
develop our understanding of geodynamic processes in
orogens.
Bibliography
Agard, P., Omrani, J., Jolivet, L., and Mouthereau, F., 2005. Convergence history across Zagros (Iran): constraints from collisional and earlier deformation. International Journal of Earth
Sciences, 94, 401–419.
Allen, P. A., and Allen, J. R., 2005. Basin Analysis: Principles and
Applications, 2nd edn. Oxford: Wiley-Blackwell.
Allken, V., Huismans, R. S., and Thieulot, C., 2012. Factors controlling the mode of rift interaction in brittle-ductile coupled systems: a 3D numerical study. Geochemistry, Geophysics,
Geosystems, 13, Q05010, doi:10.1029/2012gc004077.
Anders, B., Reischmann, T., Poller, U., and Kostopoulos, D., 2005.
Age and origin of granitic rocks of the eastern Vardar Zone,
Greece: new constraints on the evolution of the Internal
Hellenides. Journal of the Geological Society of London, 162,
857–870.
Avouac, J.-P., and Burov, E. B., 1996. Erosion as a driving mechanism of intracontinental mountain growth. Journal of Geophysical Research, 110, 17747–17769.
Beaumont, C., Ellis, S., Hamilton, J., and Fullsack, P., 1996.
Mechanical model for subduction-collision tectonics of Alpinetype compressional orogens. Geology, 24, 675–678.
Beaumont, C., Jamieson, R. A., Nguyen, M. H., and Lee, B., 2001.
Himalayan tectonics explained by extrusion of a low-viscosity
crustal channel coupled to focused surface denudation. Nature,
414, 738.
Beaumont, C., Jamieson, R. A., Nguyen, M. H., and Medvedev, S.,
2004. Crustal channel flows: 1. Numerical models with applications to the tectonics of the Himalayan-Tibetan orogen. Journal
of Geophysical Research, 109, B06406, doi:10.1029/
2003JB002809.
Becker, J. J., Sandwell, D. T., Smith, W. H. F., Braud, J., Binder, B.,
Depner, J., Fabre, D., Factor, J., Ingalls, S., Kim, S.-H., Ladner,
R., Marks, K., Nelson, S., Pharaoh, A., Trimmer, R., Von Rosenberg, J., Wallace, G., and Weatherall, P., 2009. Global bathymetry and elevation data at 30 arc seconds resolution:
SRTM30_PLUS. Marine Geodesy, 32(4), 355–371.
Braun, J., 2010. The many surface expressions of mantle dynamics.
Nature Geoscience, 3, 825–833.
Braun, J., and Yamato, P., 2010. Structural evolution of a threedimensional, finite-width crustal wedge. Tectonophysics, 484,
181–192.
Buck, W. R., 1991. Modes of continental lithospheric extension.
Journal of Geophysical Research, 96, 20,161–120,178.
OROGENY
607