Continental rifting at pre-existing lithospheric weaknesses

Dunbar, John A.; Sawyer, Dale S.

doi:10.1038/333450a0

Cited by 121 publications

(72 citation statements)

References 22 publications

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“…The numerical mesh is rectangular and composed of 62,500 to 125,000 quadruple elements each constructed of two couples of overlapped triangular elements [Cundall, 1989] 4. In the long term, extension leads to "overstrengthening" of the lithosphere, which is additional strengthening compared to the "normal strengthening" due to cooling first discussed by England [1983] and Dunbar and Sawyer [1988]. This overstrengthening is associated with structural and rheological changes provoked by thinning.…”

Section: Surface Processesmentioning

confidence: 99%

Erosion and rheology controls on synrift and postrift evolution: Verifying old and new ideas using a fully coupled numerical model

Burov¹,

Poliakov²

2001

J. Geophys. Res.

210

163

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Abstract. We use a fully coupled asymmetric dynamic finite element model to study interactions between thermomechanical behavior and surface processes during continental rift evolution. The model accounts for (1) nonlinear brittle-elastic-ductile rheology, layered lithological structure, and faulting; (2) heat transport and thermal buoyancy forces; and (3) "true" erosion and sedimentation (grid elements are eliminated and recreated). Faults are not predefined but are self-localized; their distributions and geometry are model outputs, which provides new geologically sensible constraints on its validity. We test previous ideas on rift evolution based on numerical and analytical component theories (or individual parts) of our model. After demonstrating that our coupled model reproduces classic rift features, we then demonstrate that synrift surface processes result in enhanced lithospheric thinning and widening of the basin, so that the apparent stretching factors increase by a factor of 1.5-2. Sedimentation results not only in thermal but also in localized flexural weakening of the lithosphere, which locally compensates strengthening due to cooling. Erosion on the uplifted flanks produces local strengthening and rebound. Surface processes produce pressure gradients, which drive a ductile crustal flow that (1) provides a fast feedback with tectonic processes and controls subsidence rates and flank stability and (2) drives a secondary extension or compression and uplift on the late synrift/early postrift phase. Our results indicate that kinematic and dynamic rift models that ignore erosion may produce misleading results in many rifts. We reproduced and explained a number of enigmatic synrift phenomena, such as (1) polyphase subsidence provoked by switching of the level of necking between different competent lithological layers and (2) synrift and postrift stagnation and vertical accelerations unassociated with tectonic stress inversion or phase changes.

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Section: Surface Processesmentioning

confidence: 99%

Erosion and rheology controls on synrift and postrift evolution: Verifying old and new ideas using a fully coupled numerical model

Burov¹,

Poliakov²

2001

J. Geophys. Res.

210

163

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“…The alpine structures are par allel to the grain of the Paleozoic basement and some of these lineaments of Hercynian or older age played a crucial role in the development of the Iberian Basin and the subsequent inversion tectonics during the Cenozoic compressive periods. This is a fundamental fact well illustrated, for example, in the East African Rift System (Dunbar and Sawyer, 1988;Ve rsfeld and Rosendahl, 1989;Morley et aI., 1992 ).…”

Section: Basin Boundary Faultsmentioning

confidence: 99%

“…This process has been used to explain the late orogenic extension of some orogenic be lts (McC lay et al, 1986;Menar and Molnar, 1986;Dunbar and Sawyer, 1988;Nelson, 1992) and could explain some features of the origin and evolution of the Iberian Basin and coeval basins and the lack of substan tial crustal roots, a common feature in the northern European He rcynides and the Appalachians.…”

Section: The Orientation Of the Iberian Basin And Its Relations With mentioning

confidence: 99%

Origin of the Permian-Triassic Iberian Basin, central-eastern Spain

Arché¹,

López-Gómez²

1996

Tectonophysics

130

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The Iberian Basin was an intracratonic rift basin in central-eastern Spain developed since Early Permian times. The basin boundary faults were normal, listric faults controlling an asymmetric extension propagating northeast with time.Hercynian or older lineaments controlled the orientation of the Iberian Basin and extension was accommodated basically in the hanging wall block by the formation of secondary grabens and a central high. The basin was related with the coeval Ebro, Catalan and Cuenca-Mancha Basins and their connections are discussed.Subsidence curves show that the Early Permian-Early Jurassic period of extension can be subdivided into three rifting episodes and a flexural one. Extension factor increases from 1.17 in the northwest to 1.29 near the Mediterranean coast.The increasing extension rate was accommodated by transfer faults trending NNE-SSW, more important in the Levante area. The rift evolution is intermittent and seems to reflect distinct stress fields.The collapse of the late Hercynian orogen and related increased heat flux, extension and rifting is the most probable origin of the Iberian Basin and related basins. The origin of the Catalan and the Valencia-Prebetic Basins is related to the southwards migration of the Hesse-Burgundy Rift along the eastern margin of the Iberian Microplate.

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“…This potential instability has been the subject of various proposed mechanisms for mantle lithosphere thinning, among others, mantle delamination [Bird, 1978], boundary layer instability [Houseman et al, 1981], and diapiric upwelling of the asthenosphere in a small-scale convective mode [Marechal, 1983;Buck, 1985;Keen, 1985;Buck, 1986;Dunbar and Sawyer, 1988; Keen and Boutilier, 1995; Huismans, 1999]. The potential of the instability grows with increasing perturbation.…”

Section: Introductionmentioning

confidence: 99%

Transition from passive to active rifting: Relative importance of asthenospheric doming and passive extension of the lithosphere

Huismans¹,

Podladchikov²,

Cloetingh³

2001

J. Geophys. Res.

169

118

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Abstract.We present quantitative modeling results of the dynamic interplay of passive extension and active convective thinning of the mantle lithosphere beneath intracontinental rift zones investigating the relative importance of thermal buoyancy forces associated with asthenospheric doming and far-field intraplate stresses on the style of rifting. To this aim we employ a twodimensional numerical code based on a finite element method formulation for nonlinear temperature dependent viscoelastoplastic rheology. Brittle behavior is modeled using MohrCoulomb plasticity. The models support a scenario in which passive stretching leads to an unstable lithospheric configuration. Thermal buoyancy related to this asthenospheric doming subsequently drives active upwelling in a lithosphere scale convection cell. In the late synrift to early postrift the lithospheric horizontal stresses caused by the active asthenospheric upwelling may start to compete with the far-field intraplate stresses. At this stage the domal forces may dominate and even drive the system causing a change from passive to active rifting mode. If this transition occurs, the model predicts (1) drastic increase of subcrustal thinning beneath the rift zone, (2) lower crustal flow towards the rift flanks, (3) middle crustal flow towards the rift center, (4) the coeval occurrence of tensional stresses within and compressive stresses around the upwelling region, and (5)

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Continental rifting at pre-existing lithospheric weaknesses

Cited by 121 publications

References 22 publications

Erosion and rheology controls on synrift and postrift evolution: Verifying old and new ideas using a fully coupled numerical model

Erosion and rheology controls on synrift and postrift evolution: Verifying old and new ideas using a fully coupled numerical model

Origin of the Permian-Triassic Iberian Basin, central-eastern Spain

Transition from passive to active rifting: Relative importance of asthenospheric doming and passive extension of the lithosphere

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