Lithospheric‐scale structure across the Bolivian Andes from tomographic images of velocity and attenuation for <i>P</i> and <i>S</i> waves

Myers, Stephen C.; Beck, S. L.; Zandt, G.; Wallace, Terry C.

doi:10.1029/98jb00956

Cited by 119 publications

(122 citation statements)

References 55 publications

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“…2;Whitman et al 1992;Whitman 1994;Dorbath et al 1993;Beck et al 1996;Beck and Zandt 2002;Lyon-Caen et al 1985;Watts et al 1995;Stewart and Watts 1997;Myers et al 1998;Yuan et al 2000Yuan et al , 2002Tassara 2005;Heit et al 2007;Pérez-Gussinyé et al 2008;Tassara and Echaurren 2012). These show that the high Andes form a broad region, ϳ500 km wide, where the thick crust is up to 75 km thick, but the lithosphere is less than 100 km thick.…”

Section: Lithospheric Profilesmentioning

confidence: 84%

Cenozoic uplift of the Central Andes in northern Chile and Bolivia—reconciling paleoaltimetry with the geological evolution

Lamb

2016

Can. J. Earth Sci.

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Abstract:The Cenozoic geological evolution of the Central Andes, along two transects between ϳ17.5°S and 21°S, is compared with paleo-topography, determined from published paleo-altimetry studies. Surface and rock uplift are quantified using simple 2-D models of crustal shortening and thickening, together with estimates of sedimentation, erosion, and magmatic addition. Prior to ϳ25 Ma, during a phase of amagmatic flat-slab subduction, thick-skinned crustal shortening and thickening (nominal age of initiation ϳ40 Ma) was focused in the Eastern and Western Cordilleras, separated by a broad basin up to 300 km wide and close to sea level, which today comprises the high Altiplano. Surface topography at this time in the Altiplano and the western margin of the Eastern Cordillera appears to be ϳ1 km lower than anticipated from crustal thickening, which may be due to the pull-down effect of the subducted slab, coupled to the overlying lithosphere by a cold mantle wedge. Oligocene steepening of the subducted slab is indicated by the initiation of the volcanic arc at ϳ27-25 Ma, and widespread mafic volcanism in the Altiplano between 25 and 20 Ma. This may have resulted in detachment of mantle lithosphere and possibly dense lower crust, triggering 1-1.5 km of rapid uplift (over Ͻ Ͻ5 Myrs) of the Altiplano and western margin of the Eastern Cordillera and establishing the present day lithospheric structure beneath the high Andes. Since ϳ25 Ma, surface uplift has been the direct result of crustal shortening and thickening, locally modified by the effects of erosion, sedimentation, and magmatic addition from the mantle. The rate of crustal shortening and thickening varies with location and time, with two episodes of rapid shortening in the Altiplano, lasting <5 Myrs, that are superimposed on a long-term history of ductile shortening in the lower crust, driven by underthrusting of the Brazilian Shield on the eastern margin.

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Section: Lithospheric Profilesmentioning

confidence: 84%

Cenozoic uplift of the Central Andes in northern Chile and Bolivia—reconciling paleoaltimetry with the geological evolution

Lamb

2016

Can. J. Earth Sci.

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“…Other projects carried out in the region also provided important results concerning lithospheric structure, crustal-thickness variations and lateral variations in the upper mantle (e.g. Beck et al, 1996;Dorbath and Granet, 1996;Myers et al, 1998;Dorbath and Masson, 2000;Beck and Zandt, 2002). Beneath the plateau, Myers et al, (1998) found low velocities on the eastern side towards the Eastern Cordillera suggesting lithospheric delamination.…”

Section: The Central Andes At 21°s and The Altiplano Plateaumentioning

confidence: 96%

“…Beck et al, 1996;Dorbath and Granet, 1996;Myers et al, 1998;Dorbath and Masson, 2000;Beck and Zandt, 2002). Beneath the plateau, Myers et al, (1998) found low velocities on the eastern side towards the Eastern Cordillera suggesting lithospheric delamination. By combining all geophysical and geological available data McQuarrie et al (2005) suggested that both the crust and the upper mantle should have played a key role in the lithospheric evolution of the Andean plateau and supported the idea of an ongoing removal of mantle lithosphere beneath the border between the Eastern Cordillera and the Altiplano (Beck and Zandt, 2002).…”

Section: The Central Andes At 21°s and The Altiplano Plateaumentioning

confidence: 96%

“…Although the position of these low velocities is not well constrained (due to smearing), it is important to note that it coincides with the region where data from receiver function shows an abrupt thinning of the lithosphere-astenosphere boundary and where Myers et al (1998) detected the presence of a zone of high attenuation-low velocities, which they interpreted as materials under near solidus conditions.…”

Section: -The Easternmentioning

confidence: 99%

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More constraints to determine the seismic structure beneath the Central Andes at 21°S using teleseismic tomography analysis

Heit¹,

Koulakov²,

Asch³

et al. 2008

Journal of South American Earth Sciences

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A set of seismological stations was deployed in the Central Andes region along a ~600 km long profile at 21°S between Chile and Bolivia and operated for a period of almost two years, from March 2002 to January 2004. Here we present the results of the tomographic inversion for P-wave velocity anomalies, based on teleseismic data recorded at the stations. The reliability of the results has been checked by a series of synthetic tests. The tomographic images show high-velocities on the west of the profile that are indicative of cold material from the fore-arc. A low-velocity anomaly is detected at the border between the fore-and the volcanic arc where the Quebrada Blanca seismic anomaly was previously described. This anomaly might be related to the presence of fluids that originate at the cluster of earthquakes at a depth of ~100 km in the subducted plate. A strong low-velocity anomaly is detected beneath the entire Altiplano plateau and part of the Eastern Cordillera, in agreement with previous receiver function results. The Brazilian Shield is thought to be responsible for the strong high-velocity anomaly underneath the Interandean and Subandean regions.

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“…For Beck & Zandt (2002), with given average crustal Vp and Poisson's ratio (0.25), crustal thickness in the Central Altiplano is 59-64 km, and reduces to ~50 km at 20.5°S. Lithospheric structure is also interpreted differently depending on authors, although there is a general agreement on a more asthenospheric seismic character to the south: Myers et al (1998) find that from 18°S to 20.5°S the Altiplano mantle is consistent with a mantle lithosphere down to about 125-150 km depth, and that its asthenospheric character begins at about 21°S. For Yuan et al (2002), a best fit of altitude and Bouguer anomaly with isostatic-Moho depth is obtained, assuming a felsic crust, when the lithospheric thickness is closer to 100 km than 150 km.…”

Section: Geophysical Measurements and Heterogeneity Of The Mantlementioning

confidence: 94%

Possible orogeny-parallel lower crustal flow and thickening in the Central Andes

2005

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The relatively low elevation and thick crust in the Altiplano, in comparison to the higher elevation, but thinner crust in the Puna plateau, together with geophysical data, suggest that isostatic equillibrium is achieved by cooler and denser lithospheric mantle in the Altiplano. Excess density in the Altiplano mantle could create differential horizontal stress in the order of 25 MPa between both lithospheric columns. Numerical models accounting for pressure and temperature-dependent rheology show that such stress can induce horizontal ductile flow in the lower crust, from the Puna towards the Altiplano. With a minimum viscosity of 10 19 Pa.s, this flow reaches 1 cm/yr, displacing more than 50 km of material within 5 Ma. If the lower crust viscosity is smaller, the amount of orogeny-parallel lower crustal flow can be even greater. Such a mechanism of channel flow may explain that different amounts of crustal material have been accomodated by shortening in the Altiplano and in the Puna. Because of the strength of the -brittle -upper crust, this channel flow does not necessitate large amounts of suface deformation (except vertical uplift), making it difficult to detect from the geology.

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Lithospheric‐scale structure across the Bolivian Andes from tomographic images of velocity and attenuation for P and S waves

Cited by 119 publications

References 55 publications

Cenozoic uplift of the Central Andes in northern Chile and Bolivia—reconciling paleoaltimetry with the geological evolution

Cenozoic uplift of the Central Andes in northern Chile and Bolivia—reconciling paleoaltimetry with the geological evolution

More constraints to determine the seismic structure beneath the Central Andes at 21°S using teleseismic tomography analysis

Possible orogeny-parallel lower crustal flow and thickening in the Central Andes

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