A physical model for Cenozoic extension of western North America

Sonder, Leslie J.; England, Philip; Wernicke, Brian P.; Christiansen, Robert L.

doi:10.1144/gsl.sp.1987.028.01.14

Cited by 187 publications

(110 citation statements)

References 31 publications

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“…Sonder et al (1987) modelled these phenomena and concluded that a time delay of as much as 100 million years can occur between the end of compression and initiation of extension, depending on factors such as the thermal regime of the lithosphere and particularly the Moho temperature. For a relatively hot Moho temperature (500-7008C), the time delay is near zero.…”

Section: Previous Thoughts On Crustal Thickness Of the Great Basin Dumentioning

confidence: 99%

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The Great Basin Altiplano during the middle Cenozoic ignimbrite flareup: insights from volcanic rocks

Best

Barr

Christiansen

et al. 2009

International Geology Review

106

125

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Uncertainty surrounds the fate of the orogenic plateau in what is now the Great Basin in western Utah and Nevada, which resulted from the Mesozoic and earliest Cenozoic contractile deformations and crustal thickening. Although there is some consensus regarding the gravitational collapse of the plateau by extensional faulting and consequent crustal thinning, whether or not the plateau existed during the middle Cenozoic Great Basin ignimbrite flareup -one of the grandest expressions of continental volcanism in the geologic record -had remained in doubt. We use compositions of contemporaneous calc-alkaline lava flows as well as configurations of the ignimbrite sheets to show that the Great Basin area during the middle Cenozoic was a relatively smooth plateau underlain by unusually thick crust. We compare analyses of 376 intermediate-composition lava flows in the Great Basin that were extruded at 42 -17 Ma with compositions of .6000 analyses of the late Cenozoic lava flows in continental volcanic arcs that correlate roughly with known crustal thickness. This comparison indicates that the middle Cenozoic Great Basin crust was much thicker than the present ca. 30 km thickness, likely as much as 60 -70 km. If isostatic equilibrium prevailed, this unusually thick continental crust must have supported high topography. This high terrain in SE Nevada and SW Utah was progressively smoothed as successive ignimbrite outflow sheets were emplaced over areas currently as much as tens of thousands of square kilometres to aggregate thicknesses of as much as hundreds of metres. The generally small between-site variations in the palaeomagnetic directions of individual sheets lend further support for a relatively smooth landscape over which the sheets were draped. We conclude that during the middle Cenozoic, especially towards the close of the ignimbrite flareup, this Great Basin area was a relatively flat plateau, and because it was also high in elevation, we refer to it as an Altiplano. It was not unlike the present-day Altiplano-Puna in the tectonically similar central Andes, where an ignimbrite flareup comparable to that in the Great Basin occurred at ca. 9-3 Ma. Outflow ignimbrite sheets that were deposited from 35 to 23 Ma on the progressively smoothed Altiplano in south-eastern Nevada were derived from source calderas to the west. Of the 12 major sheets from seven sources, nine are distributed unevenly east of their sources while the remaining three sheets are spread about as far east as west of their sources. This eccentricity of sources near the western margin of 75% of the sheets indicates the existence of a NS-trending topographic barrier in central Nevada that restricted westward dispersal of ash flows. In a symmetric manner, eastward dispersal of ash flows from sources farther west seemed to have been impeded by this same topographic barrier. The westward dispersal was controlled in part by westward-draining stream valleys incised in the sloping flank of the Great Basin Vol. 51, Nos. 7 -8, July-August 2009, 589-633 A...

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Section: Previous Thoughts On Crustal Thickness Of the Great Basin Dumentioning

confidence: 99%

“…Sonder et al 1987). Parcels of partial melt too small in concentration to form buoyant diapirs can nonetheless mix with ascending mantle-derived magmas.…”

Section: Ba and Rbmentioning

confidence: 99%

The Great Basin Altiplano during the middle Cenozoic ignimbrite flareup: insights from volcanic rocks

Best

Barr

Christiansen

et al. 2009

International Geology Review

106

125

View full text Add to dashboard Cite

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“…In Tibet as well as in the Basin and Range Province of the western USA, it has been argued that present-day crustal flow is strongly influenced by forces induced by large gradients in gravitational potential energy (England & Molnar 1997;Jones et al 1996;Flesch et al 2000). A warmer geotherm reduces the strength of the continental lithosphere and, as a rule of thumb, it is inferred that a thickened continental crust spreads under its own weight (i.e., Argand Ratio !1 for a given effective strain rate) when the temperature at the Moho is above c. 7008C (e.g., Sonder et al 1987).…”

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confidence: 99%

Lithospheric scale gravitational flow: the impact of body forces on orogenic processes from Archaean to Phanerozoic

Rey

Houseman

2006

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In the Archaean, the combination of warmer continental geotherm with a lighter sub-continental lithospheric mantle suggests that gravitational forces played a more significant role in continental lithospheric deformation. To test this hypothesis, we compare the evolution of the deformation and the regional state of stress in 'Archaean-like' and 'Phanerozoic-like' lithospheres submitted to the same boundary conditions in a triaxial stress-field with imposed convergence in one direction. For plausible physical parameters, thickening of normal to cold Phanerozoic lithospheres produces relatively weak buoyancy forces, either extensional or compressional. In contrast, for Archaean continental lithospheres, or for anomalously warm Phanerozoic lithospheres, lateral gravitationally-driven flow prevents significant thickening. This conclusion is broadly consistent with: (1) the relative homogeneity of the erosional level now exposed at the surface of Archaean cratons, (2) the sub-aerial conditions that prevailed during the emplacement of up to 20 km of greenstone cover, (3) the relatively rare occurrence in the Archaean record of voluminous detrital sediments, (4) the near absence of significant tectonic, metamorphic and magmatic age gradients across Archaean cratons, (5) the relative homogeneity of strain across large areas, and (6) the ubiquitous presence of crustal-scale strike slip faults in many Late Archaean cratons.One of the most contentious issues in Archaean geology is the significance of the particular features seen in the surface geology of most Archaean cratons. These involve the characteristic strain pattern of domes and basins; the ubiquity (in particular in Late-Archaean cratons) of strike-slip faults; the relative homogeneity at the craton scale of the finite strain field, the metamorphic facies and the erosion level; together with the particular timing of tectonics, magmatism, and metamorphism that seem to develop craton-wide within a very narrow time window (Binns et al.

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“…These include (1) extension, has been proposed by several authors [e.g., Coney and Harms, 1984;Mayer, 1986;Holt et al, 1986;Sonder et al, 1987;Dewey, 1988]. Subsequent extension may return the crust in these regions to an "average" crustal thickness.…”

mentioning

confidence: 99%

Lithospheric extension near Lake Mead, Nevada: A model for ductile flow in the lower crust

Kruse¹,

McNutt²,

Morgan³

et al. 1991

J. Geophys. Res.

171

117

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Small variations in gravity anomalies and topographic elevation observed in areas that have undergone highly variable amounts of upper crustal thinning can be satisfactorily explained by ductile flow of lower crustal material under the proper conditions. In this study we examine the boundary between the unextended Colorado Plateau and a strongly extended domain in the Basin and Range Province in the Lake Mead (Nevada) region. Bouguer gravity and topography data suggest that both present and preextensional variations in crustal thickness between the unextended and extended regions are small. Analytic channel flow models show that viscosities required for ductile flow in a lower crustal channel to reduce discontinuities in crustal thickness associated with variable amounts of extension are highly d•dent on the channel thickness and on the length scale of flow required. We test these hypotheses in the area around Lake Mead, Nevada, which is a transition zone between highly extended crust of the Basin and Range and the adjacent unextended Colorado Plateau.

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A physical model for Cenozoic extension of western North America

Cited by 187 publications

References 31 publications

The Great Basin Altiplano during the middle Cenozoic ignimbrite flareup: insights from volcanic rocks

The Great Basin Altiplano during the middle Cenozoic ignimbrite flareup: insights from volcanic rocks

Lithospheric scale gravitational flow: the impact of body forces on orogenic processes from Archaean to Phanerozoic

Lithospheric extension near Lake Mead, Nevada: A model for ductile flow in the lower crust

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