Optical dating of alluvial deposits at the orogenic front of the andean precordillera (Mendoza, Argentina)

Schmidt, Silke; Tsukamoto, Sumiko; Salomon, Eric; Frechen, Manfred; Hetzel, Ralf

doi:10.2478/s13386-011-0050-5

Cited by 16 publications

(23 citation statements)

References 71 publications

(68 reference statements)

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“…Geodetic data suggest horizontal displacement of ~4.5 mm/a, focused in a narrow band along the Eastern Precordillera (Brooks et al, ). Hetzel et al () and Schmidt et al (); Schmidt, Hetzel, Mingorance, & Ramos, ; Schmidt, Hetzel, Mingorance, et al, ; Schmidt et al, ) estimated shortening rates for the Las Peñas thrust at the La Escondida and Baños Colorados creeks, south of the exposures here analyzed (Figure ). They postulated shortening rates of 2 ± 0.4 and 1.2 ± 0.2 mm/a at the two sites, respectively, for the last ~12–16 ka.…”

Section: Geologic Settingmentioning

confidence: 79%

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: Geologic Settingmentioning

confidence: 79%

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

et al. 2019

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“…The age of the terraces at the Peñas fault (sites 1 and 2) was determined previously by 10 Be exposure and 14 C dating [ Schmidt et al , 2011a]. For the Cal fault, we present new 10 Be and 14 C dating results that constrain the age of the terraces at site 3, whereas optically stimulated luminescence (OSL) dating has been applied at site 4 [ Schmidt et al , 2011b].…”

Section: Tectonic Setting Of the Peñas And Cal Reverse Faultsmentioning

confidence: 99%

“…At site 4, the age of the terrace sediments on T 2 was constrained at 0.77 ± 0.15 ka (2 σ error) by optically stimulated luminescence (OSL) dating of a sand‐rich layer within the coarse‐grained gravel deposits (Figure 6b) [ Schmidt et al , 2011b]. A trench excavated at this site (Figure 5c) exposed the unconformity between the coarse‐grained terrace deposits and a sedimentary sequence composed of sand and silt layers at a depth of one meter.…”

Section: Terraces and Fault Scarps At The Peñas And Cal Faultsmentioning

confidence: 99%

Coseismic displacements and Holocene slip rates for two active thrust faults at the mountain front of the Andean Precordillera (∼33°S)

et al. 2011

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[1] During the last few hundred years several destructive earthquakes occurred along the eastern margin of the Andean Precordillera, where GPS data reveal a shortening rate of ∼4.5 mm/a. We use fault scarp profiles and age determinations of deformed terraces (T 1 -T 4 ) to infer coseismic displacements and quantify slip rates for the Peñas and Cal thrust faults near Mendoza city. Scarps on the lowest terrace level T 1 reveal vertical offsets of 0.8-1.0 m for both faults, which are interpreted as coseismic displacements during the last earthquake. Together with the fault dip these offsets indicate that both faults are capable of producing magnitude M W ∼6.9 earthquakes, which is corroborated by a magnitude M S = 7.0 event on the Cal fault that destroyed Mendoza in 1861. At the Peñas thrust fault, terrace T 2 has an age of ∼3.3 ka and is offset by ∼1.9 m, whereas the ∼12-ka-old terrace T 3 is displaced by ∼11 m. Combined with the fault dip of ∼25°, the age and offset of terrace T 3 define a shortening rate of ∼2.0 mm/a on the Peñas fault, i.e., about half of the present-day shortening at the eastern margin of the Precordillera. At the Cal fault, terraces T 2 to T 4 have ages of ∼0.8 ka (OSL), ∼3.9 ka ( 14 C), and ≤12 ka ( 10 Be) and are vertically offset by ∼2.6, ∼3.6, and ∼7.0 m, respectively, which implies that slip on the fault has recently accelerated. Hence, the Cal fault poses a serious seismic hazard to the one million inhabitants of Mendoza.Citation: Schmidt, S., R. Hetzel, F. Mingorance, and V. A. Ramos (2011), Coseismic displacements and Holocene slip rates for two active thrust faults at the mountain front

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“…Dating such geomorphic features using cosmic ray exposure (CRE) techniques has become a common method to estimate rates of tectonic deformation [e.g., Gosse and Phillips , ]. Even if this approach has been applied to several sectors in this Andean region[ Siame et al , ; Meigs et al , ; Schmidt et al , ; Hedrick et al , ], this area still lacks of a well‐constrained chronological framework for alluvial deposition and abandonment.…”

Section: Introductionmentioning

confidence: 99%

Active basement uplift of Sierra Pie de Palo (Northwestern Argentina): Rates and inception from¹⁰Be cosmogenic nuclide concentrations

et al. 2015

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Quaternary tectonic and denudation rates are investigated for an actively growing basement anticline: the Sierra Pie de Palo range, which belongs to the Andean foreland of Northwestern Argentina (28 • S-33 • S). In this study, a detailed morphometric analysis of the topography is combined with in situ-produced cosmogenic 10 Be concentrations measured in (1) surface boulders abandoned on alluvial terraces affected by fault activity (along the north bounding fault) and growth of the basement fold (along the southeastern border), (2) bedrock outcrops corresponding to an exhumed and folded, regional erosion surface, and (3) fluvial sediments sampled at the outlets of several watersheds. Along the eastern and northern borders of the range, incision and uplift rates have been estimated at approximately 0.5 and 1 mm/yr when integrated on Holocene and Pleistocene time scales, in close agreement with both long-term (structural and basin evolution data) and short-term (GPS-derived velocity field) analyses. Cosmogenic-derived denudation and uplift rates combined with geomorphic characteristics of watersheds and river channels allows estimating the onset of the uplift at 4-6 Ma, followed by a more recent period of topographic rejuvenation at roughly 1-2 Ma, probably synchronous with steepening of the eastern and northern flanks of the anticline.

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Optical dating of alluvial deposits at the orogenic front of the andean precordillera (Mendoza, Argentina)

Cited by 16 publications

References 71 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

Coseismic displacements and Holocene slip rates for two active thrust faults at the mountain front of the Andean Precordillera (∼33°S)

Active basement uplift of Sierra Pie de Palo (Northwestern Argentina): Rates and inception from¹⁰Be cosmogenic nuclide concentrations

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Optical dating of alluvial deposits at the orogenic front of the andean precordillera (Mendoza, Argentina)

Cited by 16 publications

References 71 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

Coseismic displacements and Holocene slip rates for two active thrust faults at the mountain front of the Andean Precordillera (∼33°S)

Active basement uplift of Sierra Pie de Palo (Northwestern Argentina): Rates and inception from10Be cosmogenic nuclide concentrations

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Active basement uplift of Sierra Pie de Palo (Northwestern Argentina): Rates and inception from¹⁰Be cosmogenic nuclide concentrations