Measurable impact of river incision on rift tectonics

2021 ◽  
Author(s):  
Jean-Arthur Olive ◽  
Luca Malatesta ◽  
Mark Behn ◽  
Roger Buck
Keyword(s):  
Numerical Simulations ◽  
Hanging Wall ◽  
Normal Fault ◽  
Climatic Conditions ◽  
Natural Variability ◽  
Surface Processes ◽  
Tectonic Deformation ◽  
Plate Boundaries ◽  
River Incision ◽  
Half Graben

<p>Models that couple tectonics and surface processes commonly predict that efficient erosion and sedimentation help focus crustal deformation onto fewer, longer-lived faults. However, because their geomorphic parameters are difficult to calibrate against real landscapes, the sensitivity of tectonic deformation to a realistic range of surface process efficiencies remains poorly known. Here we model the growth of structurally simple half-graben structures subjected to fluvial incision of specified efficiency and sedimentation. Numerical simulations predict that infinitely-efficient erosion and deposition (i.e., complete surface leveling) can more than double the maximum offset reached on a master normal fault before crustal strain localizes elsewhere. Further, leveling footwall relief tends to promote the migration of strain towards the hanging wall to form new grabens instead of horsts. </p><p>         To test whether the efficiency of river incision can vary sufficiently across real rifts to exert a control on tectonic styles, we analyze the profiles of rivers draining half-graben footwalls and horst blocks in the Basin & Range, Taupo, Rio Grande, and East African Rift. We adapt the standard methodology of equilibrium river profile analysis to account for spatial variations in uplift expected from crustal flexure in a fault-bounded block. Erosional efficiency (EE) is defined as the inverse of the (dimensionless) slope of uplift- and drainage area-corrected river elevation plots.  Measured EEs range between ~0.1 and ~4, reflecting natural variability in lithology, climate, and uplift rates across sites. Incorporating EEs within this documented range in numerical simulations, we find that increasing EE can increase the maximum throw on half-graben master faults by ~50%. Changing EE also affects the geometry of subsequent faults, with lower EEs favoring the transition from half-graben to horsts. These models predict that rifting in a colder, stronger continental crust is less sensitive to surface processes and requires even lower EE to develop horst structures. Our simulations are consistent with a compilation of EE, crustal strength proxies, and fault characteristics across real rift zones. These results suggest that natural variability in climatic conditions and surface erodibility has a measurable impact on the tectonic makeup of Earth's plate boundaries.</p>

scholarly journals Relevant aspects to the recognition of extensional environments in the field

2021 ◽  
Vol 48 (2) ◽  
pp. 95-106
Author(s):  
Ana Milena Suárez Arias ◽  
Julián Andrés López Isaza ◽  
Anny Juieth Forero Ortega ◽  
Mario Andrés Cuéllar Cárdenas ◽  
Carlos Augusto Quiroz Prada ◽  
...  
Keyword(s):  
Hanging Wall ◽  
Image Interpretation ◽  
Three Dimensional ◽  
Normal Fault ◽  
Structural Data ◽  
Structural Aspect ◽  
Half Graben ◽  
Regional Tectonic ◽  
History Of ◽  
Definition Of

The understanding of each geological-structural aspect in the field is fundamental to be able to reconstruct the geological history of a region and to give a geological meaning to the data acquired in the outcrop. The description of a brittle extensional environment, which is dominated by normal fault systems, is based on: (I)  image interpretation, which aims to find evidence suggestive of an extensional geological environment, such  as the presence of scarp lines and fault scarps, horst, graben and/or half-graben, among others, that allow the identification of the footwall and hanging wall blocks; ii) definition of the sites of interest for testing; and  iii) analysis of the outcrops, following a systematic procedure that consists of the observation and identification of the deformation markers, their three-dimensional schematic representation, and their  subsequent interpretation, including the stereographic representation in the outcrop. This procedure implies the unification of the parameters of structural data acquisition in the field, mentioning the minimum fields  necessary for the registration of the data in tables. Additionally, the integration of geological and structural observations of the outcrop allows to understand the nature of the geological units, the deformation related to the extensional environment and the regional tectonic context of the study area.

Tectonic deformation and magmatism along the southern flank of the Maritimes Basin: the northeastern Cobequid Highlands, Nova Scotia

2001 ◽  
Vol 38 (1) ◽  
pp. 43-58 ◽  
Author(s):  
David JW Piper ◽  
Georgia Pe-Piper
Keyword(s):  
Hanging Wall ◽  
Early Carboniferous ◽  
Tectonic Deformation ◽  
Lower Paleozoic ◽  
Oblique Convergence ◽  
Half Graben ◽  
Maritimes Basin ◽  
Seismic Reflection Profiles ◽  
Paleozoic Rocks ◽  
Structural Levels

Distributed crustal-scale faulting in the Cobequid Highlands in the Middle Devonian to Carboniferous resulted from the oblique convergence of the Meguma and Avalon terranes. In the northeastern Cobequid Highlands, seismic reflection profiles show Neoproterozoic and lower Paleozoic rocks, together with enigmatic foliated rocks, overlying the Early Carboniferous Fountain Lake Group. The foliated rocks form the hanging wall of a north-vergent thrust fault. Their protolith is inferred from petrography and geochemistry to be principally Neoproterozoic rhyodacitic tuff and late Paleozoic hypabyssal intrusions. The age of thrusting is stratigraphically constrained to the late Tournaisian – mid-Viséan, and sericite from mylonite yielded a Tournaisian K–Ar age of 352 ± 8 Ma. The thrusting occurs at the base of a tectonic escape sheet and resulted from a restraining bend in the Rockland Brook master fault. Farther west, where the Rockland Brook fault trends almost east–west, Tournaisian extensional features include the Nuttby basin and widespread gabbro dykes, sills, and stocks. At deeper structural levels, granite plutons were intruded in a similar tectonic regime of thrusting and local extension by lateral movement of basement blocks. The emplacement process resulted from progressive widening of initial dykes, analogous to the dykes deformed in the thrust hanging wall. Regionally, in the Tournaisian of the southern Maritimes Basin half-graben formation was synchronous with pluton emplacement and thrusting in adjacent horsts.

Feedbacks between magmatic intrusions, faulting, and surface processes at continental rifts

2020 ◽  
Author(s):  
Thomas Morrow ◽  
Jean-Arthur Olive ◽  
Mark Behn ◽  
Paris Smalls
Keyword(s):  
Stress Field ◽  
Normal Fault ◽  
Active Surface ◽  
Surface Processes ◽  
Plate Boundaries ◽  
Tectonic Model ◽  
Magmatic Intrusion ◽  
Narrow Region ◽  
Continental Rifts ◽  
Magmatic Intrusions

<p>During continental rifting, faulting, magmatic injection, and surface processes collectively shape the landscape. Although feedbacks between surface processes and faulting at rifts have been explored, the relationship between shallow magmatic intrusions, topography, and surface processes is poorly understood. Magmatic injection is controlled in part by lithospheric stress, and should therefore respond to rift-associated perturbations to the stress field. Along with normal fault formation and evolution, surficial mass redistribution via erosion, sediment transport, and deposition alters lithospheric stresses and has the potential to influence dike emplacement and long-term rift structure. Here we present a series of two-dimensional (2-D) numerical model runs utilizing the particle-in-cell, finite difference code SiStER to quantify the feedbacks between tectonic, magmatic, and surface processes that shape continental rifts. In our models, extension is accommodated through a combination of magmatic intrusion and tectonic stretching. Magmatic intrusion occurs within a narrow region when and where the sum of horizontal deviatoric stress and magmatic overpressure exceeds the tensile strength of the lithosphere. Magmatic overpressure is thus a key parameter that strongly modulates the sensitivity of dike emplacement to faulting, bending, and topographically-induced variations in lithosphere stress. Our results first probe the relationships between fault-related stresses and the timing and depth-distribution of magmatic intrusions at a rift with no active surface processes. In these cases, the locus of magmatic spreading migrates vertically in response to the evolving stress field. The 2-D tectonic model is then coupled to a 1-D landscape evolution model, which modifies topography concurrent with extension. In the simplest case, topographic diffusion effectively redistributes the topographic load, contributing to variations in injection-controlling lithospheric stresses. We compare our tectonic-responsive results with models that incorporate active surface processes to constrain the conditions under which surface processes modulate magmatic injection. Our simulations suggest that the development and redistribution of topography exerts an important control on the partitioning of tectonic and magmatic strain at extensional plate boundaries.</p>

THE ROLE OF SURFACE PROCESSES IN STABILIZING BASIN AND RANGE STYLE HALF-GRABEN STRUCTURES

2016 ◽  
Author(s):  
Jean-Arthur L. Olive ◽  
◽  
Luca C. Malatesta ◽  
Mark Behn ◽  
W. Roger Buck
Keyword(s):  
Basin And Range ◽  
Surface Processes ◽  
Half Graben

scholarly journals Morphotectonic Analysis along the Northern Margin of Samos Island, Related to the Seismic Activity of October 2020, Aegean Sea, Greece

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 102
Author(s):  
Paraskevi Nomikou ◽  
Dimitris Evangelidis ◽  
Dimitrios Papanikolaou ◽  
Danai Lampridou ◽  
Dimitris Litsas ◽  
...  
Keyword(s):  
Fault Zone ◽  
Seismic Activity ◽  
Volcanic Rocks ◽  
Active Tectonics ◽  
Normal Fault ◽  
Aegean Sea ◽  
Northern Margin ◽  
The North ◽  
Eastern Aegean ◽  
Half Graben

On 30 October 2020, a strong earthquake of magnitude 7.0 occurred north of Samos Island at the Eastern Aegean Sea, whose earthquake mechanism corresponds to an E-W normal fault dipping to the north. During the aftershock period in December 2020, a hydrographic survey off the northern coastal margin of Samos Island was conducted onboard R/V NAFTILOS. The result was a detailed bathymetric map with 15 m grid interval and 50 m isobaths and a morphological slope map. The morphotectonic analysis showed the E-W fault zone running along the coastal zone with 30–50° of slope, forming a half-graben structure. Numerous landslides and canyons trending N-S, transversal to the main direction of the Samos coastline, are observed between 600 and 100 m water depth. The ENE-WSW oriented western Samos coastline forms the SE margin of the neighboring deeper Ikaria Basin. A hummocky relief was detected at the eastern margin of Samos Basin probably representing volcanic rocks. The active tectonics characterized by N-S extension is very different from the Neogene tectonics of Samos Island characterized by NE-SW compression. The mainshock and most of the aftershocks of the October 2020 seismic activity occur on the prolongation of the north dipping E-W fault zone at about 12 km depth.

Control Strategies for Multistage Solar Collector Systems

1988 ◽  
Vol 110 (3) ◽  
pp. 230-232
Author(s):  
C. Saltiel
Keyword(s):  
Comparative Study ◽  
Flow Control ◽  
Numerical Simulations ◽  
Control Strategy ◽  
System Performance ◽  
Solar Collector ◽  
Control Strategies ◽  
Climatic Conditions ◽  
High Threshold ◽  
Threshold Values

A comparative study of the yearly performance of multistage solar collector systems, (comprised of more than one collector type) with a single on/off flow control strategy for all the collectors and separate on/off controls for each collector stage, is performed. Detailed numerical simulations under a range of climatic conditions showed that there is little advantage in using individual collector controls over a single on/off control strategy when the systems operate at low collector thresholds, but differences in system performance can be quite significant at high threshold values. In addition, the choice of the single control strategy (i.e., which collector the strategy is based on) at low thresholds is not critical in terms of system performance.

scholarly journals Contrasting geomorphic and stratigraphic responses to normal fault development during single and multi-phase rifting

2021 ◽  
Author(s):  
Sofia Pechlivanidou ◽  
Anneleen Geurts ◽  
Guillaume Duclaux ◽  
Robert Gawthorpe ◽  
Christos Pennos ◽  
...  
Keyword(s):  
Normal Fault ◽  
Sedimentary Facies ◽  
Surface Processes ◽  
Extension Direction ◽  
Multi Phase ◽  
Fault Growth ◽  
Stratigraphic Evolution ◽  
The Impact ◽  
Topographic Evolution ◽  
Previous Phase

Understanding the impact of tectonics on surface processes and the resultant stratigraphic evolution in multi-phase rifts is challenging, as patterns of erosion and deposition related to older phases of extension are overprinted by the subsequent extensional phases. In this study, we use a one-way coupled numerical modelling approach between a tectonic and a surface processes model to investigate topographic evolution, erosion and basin stratigraphy during single and multi-phase rifting. We compare the results from the single and the multi-phase rift experiments for a 5 Myr period during which they experience equal amounts of extension, but with the multi-phase experiment experiencing fault topography inherited from a previous phase of extension. Our results demonstrate a very dynamic evolution of the drainage network that occurs in response to fault growth and linkage and, to depocentre overfilling and overspilling. However, we observe profound differences between topographic and depocenter development during single and multi-phase rifting with implications for sedimentary facies development. Our quantitative approach, enables us to better understand the impact of changing extension direction on the distribution of sediment source areas and the syn-rift stratigraphic development through time and space.

scholarly journals Stretching and Contraction of Extensional Basins With Pre-Rift Salt: A Numerical Modeling Approach

2021 ◽  
Vol 9 ◽  
Author(s):  
Pablo Granado ◽  
Jonas B. Ruh ◽  
Pablo Santolaria ◽  
Philipp Strauss ◽  
Josep Anton Muñoz
Keyword(s):  
Hanging Wall ◽  
Structural Evolution ◽  
Extension Rate ◽  
Rift Basins ◽  
Basin Inversion ◽  
Accommodation Space ◽  
Basement Faults ◽  
Original Distribution ◽  
Thrust Belts ◽  
Half Graben

We present a series of 2D thermo-mechanical numerical experiments of thick-skinned crustal extension including a pre-rift salt horizon and subsequent thin-, thick-skinned, or mixed styles of convergence accompanied by surface processes. Extension localization along steep basement faults produces half-graben structures and leads to variations in the original distribution of pre-rift salt. Thick-skinned extension rate and salt rheology control hanging wall accommodation space as well as the locus and timing of minibasin grounding. Upon shortening, extension-related basement steps hinder forward propagation of evolving shallow thrust systems; conversely, if full basin inversion takes place along every individual fault, the regional salt layer is placed back to its pre-extensional configuration, constituting a regionally continuous décollement. Continued shortening and basement involvement deform the shallow fold-thrust structures and locally breaches the shallow décollement. We aim at obtaining a series of structural, stratigraphic and kinematic templates of fold-and-thrust belts involving rift basins with an intervening pre-rift salt horizon. Numerical results are compared to natural cases of salt-related inversion tectonics to better understand their structural evolution.

scholarly journals New constraints on the exhumation history of the western Tauern Window (European Alps) from thermochronology, thermokinematic modeling, and topographic analysis

2021 ◽  
Author(s):  
Reinhard Wolff ◽  
Ralf Hetzel ◽  
István Dunkl ◽  
Aneta A. Anczkiewicz
Keyword(s):  
Hanging Wall ◽  
Thermal Relaxation ◽  
Slip Rate ◽  
Normal Fault ◽  
European Alps ◽  
Valley Bottom ◽  
Topographic Analysis ◽  
Tauern Window ◽  
History Of ◽  
Exhumation History

AbstractThe Brenner normal fault bounds the Tauern Window to the west and accommodated a significant portion of the orogen-parallel extension in the Eastern Alps. Here, we use zircon (U–Th)/He, apatite fission track, and apatite (U–Th)/He dating, thermokinematic modeling, and a topographic analysis to constrain the exhumation history of the western Tauern Window in the footwall of the Brenner fault. ZHe ages from an E–W profile (parallel to the slip direction of the fault) decrease westwards from ~ 11 to ~ 8 Ma and suggest a fault-slip rate of 3.9 ± 0.9 km/Myr, whereas AFT and AHe ages show no spatial trends. ZHe and AFT ages from an elevation profile indicate apparent exhumation rates of 1.1 ± 0.7 and 1.0 ± 1.3 km/Myr, respectively, whereas the AHe ages are again spatially invariant. Most of the thermochronological ages are well predicted by a thermokinematic model with a normal fault that slips at a rate of 4.2 km/Myr between ~ 19 and ~ 9 Ma and produces 35 ± 10 km of extension. The modeling reveals that the spatially invariant AHe ages are caused by heat advection due to faulting and posttectonic thermal relaxation. The enigmatic increase of K–Ar phengite and biotite ages towards the Brenner fault is caused by heat conduction from the hot footwall to the cooler hanging wall. Topographic profiles across an N–S valley in the fault footwall indicate 1000 ± 300 m of erosion after faulting ceased, which agrees with the results of our thermokinematic model. Valley incision explains why the Brenner fault is located on the western valley shoulder and not at the valley bottom. We conclude that the ability of thermokinematic models to quantify heat transfer by rock advection and conduction is crucial for interpreting cooling ages from extensional fault systems.

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