Lateral extrusion in the eastern Alps, PArt 2: Structural analysis

Lateral extrusion in the eastern Alps, PArt 2: Structural analysis The late Oligocene‐Miocene tectonic style of the Alps is variable along strike of the orogen. In the Western and Central Alps, foreland imbrication, backthrusting, and backfolding dominate. In the Eastern Alps, strike‐slip and normal faults prevail. These differences are due to lateral extrusion in the Eastern Alps. Lateral extrusion encompasses tectonic escape (plane strain horizontal motion of tectonic wedges driven by forces applied to their boundaries) and extensional collapse (gravitational spreading away from a topographic high in an orogenic belt). The following factors contributed to the establishment of lateral extrusion in the Eastern Alps: (1) a rigid foreland, (2) a thick crust created by indentation and earlier collision, (3) a decrease in strength in the crust due to thermal relaxation, (4) a crustal thickness gradient from the Eastern Alps to the Carpathians, and, possibly, (5) a disturbance of the lithospheric root. Northward indentation by the Southern Alps causes thickening in and in front of the indenter and tectonic escape. Gravitational spreading attenuates crustal thickness differences. Indentation structures occur in the western Eastern Alps and comprise folds, thrusts, and strike‐slip faults. These structures pass laterally into spreading structures, which encompass transtensional and normal faults in the eastern Eastern Alps. The overall structural pattern is dominated by escape structures, namely, sets of strike‐slip faults that bound serially extruding wedges. Structural complexity arises from (1) interference of major fault sets, (2) accommodation of displacement differences between the Eastern Alps and their fore‐ and hinterland, (3) displacement transfer from the Eastern Alps toward the Carpathians which act as a lateral unconstrained margin, and (4) crustal decoupling, which partitions extrusion into brittle upper plate and ductile lower plate deformation. The kinematics of lateral extrusion is approximated by an extrusion‐spreading model proposed for nappe tectonics. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Tectonics Wiley

Lateral extrusion in the eastern Alps, PArt 2: Structural analysis

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Publisher
Wiley
Copyright
Copyright © 1991 by the American Geophysical Union.
ISSN
0278-7407
eISSN
1944-9194
DOI
10.1029/90TC02623
Publisher site
See Article on Publisher Site

Abstract

The late Oligocene‐Miocene tectonic style of the Alps is variable along strike of the orogen. In the Western and Central Alps, foreland imbrication, backthrusting, and backfolding dominate. In the Eastern Alps, strike‐slip and normal faults prevail. These differences are due to lateral extrusion in the Eastern Alps. Lateral extrusion encompasses tectonic escape (plane strain horizontal motion of tectonic wedges driven by forces applied to their boundaries) and extensional collapse (gravitational spreading away from a topographic high in an orogenic belt). The following factors contributed to the establishment of lateral extrusion in the Eastern Alps: (1) a rigid foreland, (2) a thick crust created by indentation and earlier collision, (3) a decrease in strength in the crust due to thermal relaxation, (4) a crustal thickness gradient from the Eastern Alps to the Carpathians, and, possibly, (5) a disturbance of the lithospheric root. Northward indentation by the Southern Alps causes thickening in and in front of the indenter and tectonic escape. Gravitational spreading attenuates crustal thickness differences. Indentation structures occur in the western Eastern Alps and comprise folds, thrusts, and strike‐slip faults. These structures pass laterally into spreading structures, which encompass transtensional and normal faults in the eastern Eastern Alps. The overall structural pattern is dominated by escape structures, namely, sets of strike‐slip faults that bound serially extruding wedges. Structural complexity arises from (1) interference of major fault sets, (2) accommodation of displacement differences between the Eastern Alps and their fore‐ and hinterland, (3) displacement transfer from the Eastern Alps toward the Carpathians which act as a lateral unconstrained margin, and (4) crustal decoupling, which partitions extrusion into brittle upper plate and ductile lower plate deformation. The kinematics of lateral extrusion is approximated by an extrusion‐spreading model proposed for nappe tectonics.

Journal

TectonicsWiley

Published: Apr 1, 1991

References

  • Alpine metamorphism in the south‐east Tauern Window, Austria, 2, Rates of heating, cooling and uplift
    Cliff, Cliff; Droop, Droop; Rex, Rex
  • Lateral extrusion in the Eastern Alps, 1, Boundary conditions and experiments scaled for gravity
    Ratschbacher, Ratschbacher; Merle, Merle; Davy, Davy; Cobbold, Cobbold
  • Evolution of the Pannonian Basin system, 1, Tectonics
    Royden, Royden; Horváath, Horváath; Rumpler, Rumpler
  • Transition from near‐surface thrusting to intrabasement decollement, Schlinig thrust, Eastern Alps
    Schmid, Schmid; Haas, Haas
  • Petrologic constraints on imbrication, metamorphism and uplift in the SW Tauern Window, Eastern Alps
    Selverstone, Selverstone
  • Evidence for east‐west crustal extension in the Eastern Alps: Implications for the unroofing history of the Tauern Window
    Selverstone, Selverstone

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