Quaternary-active thrusts scarps tested as deformation markers by trishear models in the Southern Precordillera of Argentina

Vazquez, Fabricio Rodrigo; Costa, Carlos H.; Gardini, Carlos

doi:10.1016/j.quaint.2016.06.020

Cited by 6 publications

(9 citation statements)

References 35 publications

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“…Alluvial surfaces have been used in many active contractional settings as cumulative deformation markers (e.g., Avouac et al, ; Benedetti et al, ; Bullard & Lettis, ; Davis et al, ; Dolan et al, ; García et al, ; Gold et al, ; Ishiyama et al, , ; Lin et al, ; Mueller & Suppe, ; Vázquez et al, , among others). However, the use of scarp morphometry with these purposes at a detailed scale could be misleading, because scarp profiles are usually modified during and after thrust propagation by processes such as erosion and mass‐transfer.…”

Section: Methodsmentioning

confidence: 99%

“…Thrust propagation at the scale of the study site can also result in inconsistencies between the inner geometry of folding in comparison with the shape of the topographic surface, as predicted by mechanical models and classical sandbox experiments (Cardozo et al, ; Hardy & Allmendinger, ; Hardy & Finch, ; Johnson & Johnson, ; Takao et al, ). These issues prevent modeling the accumulated thrust shortening by restoring the current scarp profile through line‐balancing methods (Woodward et al, ), which can account for the uplift produced by the thrust displacement but may result in underestimating shortening and the related slip of the structure (Vázquez et al, ). We also did not apply the balancing methods proposed by Suppe and Medwedeff (), because nonparallel‐type folding of the Quaternary cover related to the propagation of the Las Peñas thrust has been reported for this structure elsewhere (Schmidt, Hetzel, Mingorance, & Ramos, ; Vázquez et al, ).…”

Section: Methodsmentioning

confidence: 99%

“…These issues prevent modeling the accumulated thrust shortening by restoring the current scarp profile through line‐balancing methods (Woodward et al, ), which can account for the uplift produced by the thrust displacement but may result in underestimating shortening and the related slip of the structure (Vázquez et al, ). We also did not apply the balancing methods proposed by Suppe and Medwedeff (), because nonparallel‐type folding of the Quaternary cover related to the propagation of the Las Peñas thrust has been reported for this structure elsewhere (Schmidt, Hetzel, Mingorance, & Ramos, ; Vázquez et al, ). Therefore, in order to reconstruct possible geometries using the upper topographic envelope as a deformation marker, trishear modeling was applied, aiming to link scarp geometries and known fault parameters with kinematically balanced sections (e.g., Allmendinger, ; Erslev, ; Hardy & Allmendinger, ; Hardy & Ford, ; Zehnder & Allmendinger, ).…”

Section: Methodsmentioning

confidence: 99%

“…The surface signature of the Las Peñas thrust can be recognized for more than 30 km along strike (Figure ). Although primary fault‐related morphologies are poorly preserved, fold‐related scarps with different degrees of preservation are present along much of the fault trace (Ahumada & Costa, ; Costa et al, ; Costa, Diederix, et al, ; Schmidt, Hetzel, Mingorance, & Ramos, ; Vázquez et al, ). The hanging wall of the Las Peñas thrust is covered in places by thin remnants (generally <5 m) of alluvial deposits (coarse gravels).…”

Section: Geologic Settingmentioning

confidence: 99%

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Assessing Quaternary Shortening Rates at an Andean Frontal Thrust (32°30′S), Argentina

et al. 2019

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At the latitude of 32–33°S, the orogenic front of the eastern flank of the Andes is located in the Southern Precordillera, where two major thrusts concentrate Quaternary deformation at the surface. We estimate the shortening rate for one of these, the Las Peñas thrust, for the last ~200 ka, at the site of one of the best exposures of Quaternary thrusting along the Andes. Shortening was estimated across two prominent splays of the deformation zone at the mouth of the Las Peñas River through balanced cross‐sections by using a terrace surface as a marker of cumulative deformation. Terrace ages were constrained through cosmogenic isotopes (10Be) analysis on quartz cobbles collected from the surface and three depth profiles. Results indicate a mean shortening rate across the Las Peñas thrust of 0.27 + 0.11 mm/a. Our results are lower than Holocene shortening rates (1.9–2.4 mm/a) obtained for individual splays of the Las Peñas thrust nearby. We discuss these discrepancies and implications for thrust evolution since the Late Pleistocene, in particular regarding along‐strike rate variations that highlight the complexity of the Quaternary‐active thrust deformation zone. We argue that ongoing stream incision rates largely prevail with respect to thrust activity at the study site. This observation might be connected with a recent (Holocene?) basinward shift of blind thrust activity.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Geologic Settingmentioning

confidence: 99%

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Assessing Quaternary Shortening Rates at an Andean Frontal Thrust (32°30′S), Argentina

et al. 2019

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“…However, uncertainty for the displacement measurements cannot be quantified because best fit is based on visual inspection. Several studies which use FFF modeling as one of the approaches to measure displacement on reverse fault scarps also in Argentina used this same trial‐and‐error and visual estimation approach for determining the model that best fits the actual faulted profile (Costa, Ahumada, Vázquez, & Kröhling, ; Vázquez et al, ). Using the fault dip value at the surface, the displacement was then resolved into components of shortening and uplift.…”

Section: Methodsmentioning

confidence: 99%

Late Quaternary Activity of the La Rinconada Fault Zone, San Juan, Argentina

et al. 2019

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Most of the permanent deformation in the Pampean Flat slab segment of the central Andes is taken up at the Andean Orogenic Front in Argentina, a narrow zone between the Eastern Precordillera and Sierras Pampeanas that comprises one of the world's most seismically active thrust zones. Active faults and folds in the region have been extensively mapped but still largely lack information on style and rates of deformation, which is essential for understanding the distribution of regional strain and estimating the seismic potential of individual faults. Structural, geomorphic, and 36 Cl cosmogenic radionuclide surface exposure age methods are used to focus on key sites along the 30-km-long La Rinconada Fault Zone in this region of west-central Argentina, which is~15 km away from the highly populated (~500,000) city of San Juan, to define a late Quaternary average shortening rate of 0.41 ± 0.01 mm/year. This slip rate is the same order of magnitude, but slightly lower than nearby similar east dipping Eastern Precordillera faults including the La Laja and Las Tapias Faults. Relatively low slip rates are interpreted as being a consequence of distributed deformation between the latitude of the La Rinconada Fault Zone (31 and 32°S), as compared to between latitudes 32 to 33°S where deformation appears to be focused on fewer structures, including the Las Peñas and La Cal Thrust Faults. The La Rinconada Fault Zone is capable of generating earthquakes of M w 6.6-7.2, but further investigations are required to determine timing and recurrence intervals of discrete events.

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Quaternary tectonic evolution of the Pamir‐Tian Shan convergence zone, Northwest China

Jobe

Chen

et al. 2017

Tectonics

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The Pamir‐Tian Shan collision zone in the western Tarim Basin, northwest China, formed from rapid and ongoing convergence in response to the Indo‐Eurasian collision. The arid landscape preserves suites of fluvial terraces crossing structures active since the late Neogene that create fault and fold scarps recording Quaternary deformation. Using geologic and geomorphic mapping, differential GPS surveys of deformed terraces, and optically stimulated luminescence dating, we create a synthesis of the active structures that delineate the timing, rate, and migration of Quaternary deformation during ongoing convergence. New deformation rates on eight faults and folds, when combined with previous studies, highlight the spatial and temporal patterns of deformation within the Pamir‐Tian Shan convergence zone during the Quaternary. Terraces spanning ~130 to ~8 ka record deformation rates between ~0.1 and 5.6 mm/yr on individual structures. In the westernmost Tarim Basin, where the Pamir and Tian Shan are already juxtaposed, the fastest rates occur on actively deforming structures at the interface of the Pamir‐Tian Shan orogens. Farther east, as the separation between the Pamir‐Tian Shan orogens increases, the deformation has not been concentrated on a single structure, but rather has been concurrently distributed across a zone of faults and folds in the Kashi‐Atushi fold‐and‐thrust belt and along the NE Pamir margin, where shortening rates vary on individual structures during the Quaternary. Although numerous structures accommodate the shortening and the locus of deformation shifts during the Quaternary, the total shortening across the western Tarim Basin has remained steady and approximately matches the current geodetic rate of 6–9 mm/yr.

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Quaternary-active thrusts scarps tested as deformation markers by trishear models in the Southern Precordillera of Argentina

Cited by 6 publications

References 35 publications

Assessing Quaternary Shortening Rates at an Andean Frontal Thrust (32°30′S), Argentina

Assessing Quaternary Shortening Rates at an Andean Frontal Thrust (32°30′S), Argentina

Late Quaternary Activity of the La Rinconada Fault Zone, San Juan, Argentina

Quaternary tectonic evolution of the Pamir‐Tian Shan convergence zone, Northwest China

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