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Spatial and temporal evolution of foredeep basins: lateral strength variations and inelastic yielding in continental lithosphere
Author(s) -
Waschbusch PAULA J.,
Royden LEIGH H.
Publication year - 1992
Publication title -
basin research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.522
H-Index - 83
eISSN - 1365-2117
pISSN - 0950-091X
DOI - 10.1111/j.1365-2117.1992.tb00044.x
Subject(s) - foreland basin , geology , lithosphere , lithospheric flexure , flexural rigidity , seismology , structural basin , paleontology , tectonics , physics , thermodynamics
Lateral strength variations in foreland lithosphere in front of an advancing subduction zone (or thrust belt) can exert strong controls on the spatial and temporal evolution of the foredeep basin because local weak zones within the foreland serve to localize the position of the outer flexural bulge (with respect to the foreland) for extended periods of time. This occurs because the weak segment bends more easily than the surrounding, suffer plate, so that plate bending is concentrated within the weak zone. With time, the dip of the down‐going (foreland) plate becomes steeper, narrowing and/or deepening the foredeep basin. If several weak zones are present within the foreland, basin development can become episodic, with protracted periods of time during which the basin remains fixed with respect to the foreland, interspersed by brief periods of time during which the basin advances rapidly toward the foreland. The flexural behaviour will be directly reflected in the stratigraphic record, producing facies belts which migrate toward the foreland in an episodic fashion. If the foreland lithosphere behaves as an elastic sheet, the weak zones must have a flexural rigidity about an order of magnitude lower than (or an elastic plate thickness about half of) the surrounding, stiffer plate in order to induce strongly episodic behaviour. When the effects of inelastic yielding in a lithosphere of brittle‐elastic‐ductile rheology are considered, the strength contrast required to produce episodic behaviour is reduced to about a factor of two in flexural rigidity (or 10–15 % in initial elastic plate thickness). Examples taken from two foredeep basins show evidence for episodic foredeep basin development: in both the early Proterozoic Kilohigok basin of northern Canada and the Pliocene‐Quaternary Apennine foredeep basin beneath the Adriatic Sea, the outer flexural bulge appears to have remained fixed with respect to the foreland while the inner part of the basin deepened through time. In addition, the flexural geometry of the Pliocene‐Quaternary Apennine foredeep basin is well modelled by an elastic plate varying laterally in strength of thickness T elastic =8.5 km with a 20 km‐long weak zone of thickness T weak = 4.25 km.