Migrating deformation in the Central Andes from enhanced orographic rainfall

Norton, Kevin; Schlunegger, Fritz

doi:10.1038/ncomms1590

Cited by 44 publications

(25 citation statements)

References 57 publications

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“…The clustering of young (<15 Ma) AFT cooling ages in the central EC is a function of the active basement ramp, which is linked to shortening in the SAZ. Previous interpretations of this recent cooling expressed as young AFT ages include active deformation manifested as surface breaking faults or subsurface accretion (Norton & Schlunegger, ), focused erosion driven by an increase in precipitation (Barnes et al, ; Gillis et al, ; Lease & Ehlers, ), and uplift over a basement ramp (Whipple & Gasparini, ). Our modeling shows that the motion of crustal material over the basement sheet B ramp focuses 5–8 km of exhumation in this region resetting cooling signals in a westward younging pattern.…”

Section: Discussionmentioning

confidence: 97%

Kinematics, Exhumation, and Sedimentation of the North Central Andes (Bolivia): An Integrated Thermochronometer and Thermokinematic Modeling Approach

2017

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Quantifying mountain building processes in convergent orogens requires determination of the timing and rate of deformation in the overriding plate. In the central Andes, large discrepancies in both timing and rate of deformation prevent evaluating the shortening history in light of internal or external forcing factors. Geologic map patterns, age and location of reset thermochronometer systems, and synorogenic sediment distribution are all a function of the geometry, kinematics, and rate of deformation in a fold‐thrust‐belt‐foreland basin (FTB‐FB) system. To determine the timing and rate of deformation in the northern Bolivian Andes, we link thermokinematic modeling to a sequentially forward modeled, balanced cross section isostatically accounting for thrust loads and erosion. Displacement vectors, in 10 km increments, are assigned variable ages to create velocity fields in a thermokinematic model for predicting thermochronometer ages. We match both the pattern of predicted cooling ages with the across strike pattern of measured zircon fission track, apatite fission track, and apatite (U‐Th)/He cooling ages as well as the modeled age of FB formations to published sedimentary sections. Results indicate that northern Bolivian FTB deformation started at 50 Ma and may have begun as early as 55 Ma. Acceptable rates of shortening permit either a constant rate of shortening (~4–5 mm/yr) or varying shortening rates with faster rates (7–10 mm/yr) at 45–50 Ma and 12–8 Ma, significantly slower rates (2–4 mm/yr) from 35 to 15 Ma and indicate the northern Bolivian Subandes started deforming between 19 and 14 Ma.

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Section: Discussionmentioning

confidence: 97%

Kinematics, Exhumation, and Sedimentation of the North Central Andes (Bolivia): An Integrated Thermochronometer and Thermokinematic Modeling Approach

2017

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“…As any of the aforementioned processes would have promoted additional crustal thickening, if sufficient in scale, they may have generated an appropriately large orogenic edifice to promote further frictional resistance and heightened coupling along the plate boundary (Iaffaldano & Bunge, ; Meade & Conrad, ). In fact, the central Andes may have reached a threshold condition, whereby mountain building became self reinforcing, with (a) the growth of sizeable topography and a thick hinterland backstop (Barnes & Ehlers, ; Oncken et al, ), (b) aridification of forearc regions and further starving of the trench (Lamb & Davis, ; Norton & Schlunegger, ; Strecker et al, ), and/or (c) cyclical buildup and removal of dense orogenic roots (DeCelles et al, , ). Although speculative, it is posited here that a late middle Eocene to earliest Miocene phase of flat slab subduction, which did not affect the southern Andes, provided a trigger for enhanced coupling and protracted contractional growth of the central Andes.…”

Section: Discussionmentioning

confidence: 99%

Tectonic Regimes of the Central and Southern Andes: Responses to Variations in Plate Coupling During Subduction

2018

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Construction of the Andes has been governed largely by fluctuating contractional, neutral, and extensional tectonic regimes during differing degrees of mechanical coupling along the convergent plate boundary. These three contrasting regimes are likely regulated by geodynamic variations in absolute trenchward motion of South America and episodic regional shifts in the geometry of the subducting oceanic slab. Alternations among these three modes are revealed in syntheses of Mesozoic‐Cenozoic crustal deformation, basin evolution, and arc magmatism along orogen‐perpendicular transects across the central and southern Andes at 23°S, 35°S, and 43°S. Despite considerable along‐strike dissimilarities in the magnitude of deformation, a comparable tectonic regime typified the early Andean history, as defined by a transition from Late Jurassic‐Early Cretaceous postrift thermal subsidence to Late Cretaceous retroarc shortening. A key contradiction is expressed for the late middle Eocene to earliest Miocene, when neutral to extensional conditions affected retroarc to forearc regions, except in parts of the central Andes, which experienced retroarc shortening with only localized forearc extension. This mixed‐mode scenario during Paleogene time may reflect decoupling along the plate boundary (possibly during slab rollback within a retreating subduction system) in which widespread stasis or low‐magnitude extension dominated the southern Andes but was inhibited in the strongly shortened central Andes at 15–25°S where shallow subduction and/or high topography boosted plate coupling. Comparable temporal and spatial shifts in tectonic regime along the Andes and other convergent margins can be related to variable degrees of coupling during first‐order plate‐scale changes in convergence and second‐order regional cycles of slab shallowing and steepening.

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“…(, ); Schlunegger et al . (); Norton and Schlunegger (), a fixed reference concavity ( θ ref = 0.45) was used to calculate a normalized steepness index ( k sn ). Using a reference concavity overcomes the inherent correlation of regression slope and intercept in Equation , and facilitates comparison of gradients in channels with widely varying drainage areas.…”

Section: Methodsmentioning

confidence: 99%

Tracking sediment provenance and erosional evolution of the western Greater Caucasus

Vezzoli

Garzanti

Vincent

et al. 2014

Earth Surf Processes Landf

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This article investigates landscape characteristics and sediment composition in the western Greater Caucasus by using multiple methods at different timescales. Our ultimate goal is to compare short‐term versus long‐term trends in erosional processes and to reconstruct spatio‐temporal changes in sediment fluxes as controlled by partitioning of crustal shortening and rock uplift in the orogenic belt. Areas of active recent uplift are assessed by quantitative geomorphological techniques [digital elevation model (DEM) analysis of stream profiles and their deviation from equilibrium] and compared with regions of rapid exhumation over longer time intervals as previously determined by fission‐track and cosmogenic‐nuclide analyses. Complementary information from petrographic and heavy‐mineral analyses of modern sands and ancient sandstones is used to evaluate erosion integrated throughout the history of the orogen. River catchments displaying the highest relief, as shown by channel‐steepness indices, correspond with the areas of most rapid exhumation as outlined by thermochronological data. The region of high stream gradients is spatially associated with the highest topography around Mount Elbrus, where sedimentary cover strata have long been completely eroded and river sediments display the highest metamorphic indices and generally high heavy‐mineral concentrations. This study reinforces the suggestion that the bedrock–channel network can reveal much of the evolution of tectonically active landscapes, and implies that the controls on channel gradient ultimately dictate the topography and the relief along the Greater Caucasus. Our integrated datasets, obtained during a decade of continuing research, display a general agreement and regularity of erosion patterns through time, and consistently indicate westward decreasing rates of erosional unroofing from the central part of the range to the Black Sea. Copyright © 2014 John Wiley & Sons, Ltd.

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Migrating deformation in the Central Andes from enhanced orographic rainfall

Cited by 44 publications

References 57 publications

Kinematics, Exhumation, and Sedimentation of the North Central Andes (Bolivia): An Integrated Thermochronometer and Thermokinematic Modeling Approach

Kinematics, Exhumation, and Sedimentation of the North Central Andes (Bolivia): An Integrated Thermochronometer and Thermokinematic Modeling Approach

Tectonic Regimes of the Central and Southern Andes: Responses to Variations in Plate Coupling During Subduction

Tracking sediment provenance and erosional evolution of the western Greater Caucasus

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