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>

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 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.

How syn-rift sedimentation promotes the formation of hyper-extended margins

2020 ◽  
Author(s):  
Susanne Buiter
Keyword(s):  
Sedimentary Basins ◽  
Surface Processes ◽  
Tectonic Activity ◽  
Tectonic Deformation ◽  
Continental Margins ◽  
Rifted Margins ◽  
Continental Rifts ◽  
Break Up ◽  
Mountain Belts ◽  
Sediment Layers

<p>Seismic observations show that some rifted continental margins may have substantial amounts of offshore sediments. For example, sediment layers of several kilometres thick are found on the margins of Mid Norway, Namibia and Angola. Intriguingly, these margins are wide, being characterised by distances of several hundreds of kilometres from typical continental crustal thicknesses of 30-40 km to clearly identifiable oceanic crust. On the other hand, some margins that are sediment-starved, such as Goban Spur, Flemish Cap and Northern Norway, have short onshore-to-offshore transitions. Variations in the amount of sediments not only impact the development of offshore sedimentary basins, but the changes in mass balance by erosion and sedimentation can also interact with extensional tectonic processes. In convergent settings, such feedback relationships between erosion and tectonic deformation have long been highlighted: Erosion reduces the elevation and width of mountain belts and in turn tectonic activity and exhumation are focused at regions of enhanced erosion. But what is the role played by surface processes during formation of rifted continental margins?</p><p>I use geodynamic finite-element experiments to explore the response of continental rifts to erosion and sedimentation from initial rifting to continental break-up. The experiments predict that rifted margins with thick syn-rift sedimentary packages are more likely to form hyper-extended crust and require more stretching to achieve continental break-up than sediment-starved margins. These findings imply that surface processes can control the style of continental break-up and that the role of sedimentation in rifted margin evolution goes far beyond the simple exertion of a passive weight.</p>

Imaging Active Surface Processes in Barnacle Adhesive Interfaces

Langmuir ◽  
2016 ◽  
Vol 32 (2) ◽  
pp. 541-550 ◽  
Author(s):  
Joel P. Golden ◽  
Daniel K. Burden ◽  
Kenan P. Fears ◽  
Daniel E. Barlow ◽  
Christopher R. So ◽  
...  
Keyword(s):  
Active Surface ◽  
Surface Processes

How a strong low-angle normal fault formed: The Whipple detachment, southeastern California

2019 ◽  
Vol 132 (9-10) ◽  
pp. 1817-1828 ◽  
Author(s):  
Gary J. Axen
Keyword(s):  
Principal Stress ◽  
Maximum Shear Stress ◽  
Fluid Pressure ◽  
Normal Fault ◽  
Maximum Principal Stress ◽  
Detachment Fault ◽  
Normal Faults ◽  
Small Scale ◽  
Tectonic Model ◽  
Stress Rotation

Abstract Many low-angle normal faults (dip ≤30°) accommodate tens of kilometers of crustal extension, but their mechanics remain contentious. Most models for low-angle normal fault slip assume vertical maximum principal stress σ1, leading many authors to conclude that low-angle normal faults are poorly oriented in the stress field (≥60° from σ1) and weak (low friction). In contrast, models for low-angle normal fault formation in isotropic rocks typically assume Coulomb failure and require inclined σ1 (no misorientation). Here, a data-based, mechanical-tectonic model is presented for formation of the Whipple detachment fault, southeastern California. The model honors local and regional geologic and tectonic history and laboratory friction measurements. The Whipple detachment fault formed progressively in the brittle-plastic transition by linking of “minidetachments,” which are small-scale analogs (meters to kilometers in length) in the upper footwall. Minidetachments followed mylonitic anisotropy along planes of maximum shear stress (45° from the maximum principal stress), not Coulomb fractures. They evolved from mylonitic flow to cataclasis and frictional slip at 300–400 °C and ∼9.5 km depth, while fluid pressure fell from lithostatic to hydrostatic levels. Minidetachment friction was presumably high (0.6–0.85), based upon formation of quartzofeldspathic cataclasite and pseudotachylyte. Similar mechanics are inferred for both the minidetachments and the Whipple detachment fault, driven by high differential stress (∼150–160 MPa). A Mohr construction is presented with the fault dip as the main free parameter. Using “Byerlee friction” (0.6–0.85) on the minidetachments and the Whipple detachment fault, and internal friction (1.0–1.7) on newly formed Reidel shears, the initial fault dips are calculated at 16°–26°, with σ1 plunging ∼61°–71° northeast. Linked minidetachments probably were not well aligned, and slip on the evolving Whipple detachment fault probably contributed to fault smoothing, by off-fault fracturing and cataclasis, and to formation of the fault core and fractured damage zone. Stress rotation may have occurred only within the mylonitic shear zone, but asymmetric tectonic forces applied to the brittle crust probably caused gradual rotation of σ1 above it as a result of: (1) the upward force applied to the base of marginal North America by buoyant asthenosphere upwelling into an opening slab-free window and/or (2) basal, top-to-the-NE shear traction due to midcrustal mylonitic flow during tectonic exhumation of the Orocopia Schist. The mechanical-tectonic model probably applies directly to low-angle normal faults of the lower Colorado River extensional corridor, and aspects of the model (e.g., significance of anisotropy, stress rotation) likely apply to formation of other strong low-angle normal faults.

THE OTWAY BASIN: EARLY CRETACEOUS RIFTING TO NEOGENE INVERSION

1995 ◽  
Vol 35 (1) ◽  
pp. 494 ◽  
Author(s):  
A.J. Buffin ◽  
A.J. Sutherland ◽  
J.A. Gorski
Keyword(s):  
Stress Field ◽  
Normal Fault ◽  
Horizontal Wells ◽  
Horizontal Stress ◽  
Natural Fracture ◽  
Water Flooding ◽  
Hydraulic Fractures ◽  
Vertical Wells ◽  
Minimum Horizontal Stress ◽  
Maximum Horizontal Stress

Borehole breakouts and hydraulic fractures in­ferred from dipmeter and formation microscanner logs indicate that the minimum horizontal stress (σh) is oriented 035°N in the South Australian sector of the Otway Basin. Density and sonic check-shot log data indicate that vertical stress (σv) increases from approximately 20 MPa at a depth of one km to 44 MPa at two km and 68 MPa at three km. Assum­ing a normal fault condition (i.e. σy > σH > σh), the magnitude of σh is 75 per cent of the magnitude of the maximum horizontal stress (σH), and the magni­tude of σH is close to that of av. Sonic velocity compaction trends for shales suggest that pore pressure is generally near hydrostatic in the Otway Basin.Knowledge of the contemporary stress field has a number of implications for hydrocarbon produc­tion and exploration in the basin. Wellbore quality in vertical wells may be improved (breakouts sup­pressed) by increasing the mud weight to a level below that which induces hydraulic fracture, or other drilling problems related to excessive mud weight. Horizontal wells drilled in the σh direction (035°N/215°N) should be more stable than those drilled in the σH direction, and indeed than vertical wells. In any EOR operations where water flooding promotes hydraulic fracturing, injectors should be aligned in the aH (125°N/305°N) direction, and off­set from producers in the orthogonal σh direction. Any deviated/horizontal wells targeting the frac­tured basement play should be oriented in the σh (035°N/215°N) direction to maximise intersection with this open, natural fracture trend. Hydrocar­bon recovery in wells deviated towards 035°N/215°N may also be enhanced by inducing multiple hydrau­lic fractures along the wellbore.Considering exploration-related issues, faults following the dominant structural trend, sub-paral­lel to σH orientation, are the most prone to be non-sealing during any episodic build-up of pore pres­sure. Pre-existing vertical faults striking 080-095°N and 155-170°N are the most prone to at least a component of strike-slip reactivation within the contemporary stress field.

Characteristics of Seismicity in the Eagle Ford Shale Play, Southern Texas, Constrained by Earthquake Relocation and Centroid Moment Tensor Inversion

2021 ◽  
Author(s):  
Peng Li ◽  
Guo-Chin D. Huang ◽  
Alexandros Savvaidis ◽  
Florentia Kavoura ◽  
Robert W. Porritt
Keyword(s):  
Stress Field ◽  
Energy Release ◽  
Fault Plane ◽  
Anthropogenic Activities ◽  
Moment Tensor ◽  
Normal Fault ◽  
Strike Slip ◽  
Eagle Ford Shale ◽  
Eagle Ford ◽  
Earthquake Energy

Abstract Analysis of earthquake locations and centroid moment tensors (CMTs) is critical in assessing seismogenic structures and connecting earthquakes to anthropogenic activities. The objective of this study was to gain insights into the seismotectonics of the Eagle Ford Shale play (EF), southern Texas, through relative relocation of earthquakes, assessment of CMT solutions, and investigation of the background stress field. Using Texas Seismological Network (TexNet) data from 2017 through 2019, we were able to relocate 326 earthquakes and obtain CMT solutions for 37 ML≥2.0 earthquakes. These earthquakes are located in the sedimentary basin and uppermost crust, with depths ranging from 2 to 10 km. The earthquake groups in the northeastern EF are linearly distributed along the Karnes fault zone, whereas the southern and western groups are spatially scattered around mapped or unmapped faults. CMT solutions identified 32 normal fault earthquakes and five strike-slip earthquakes. The orientation of the fault plane of most normal fault earthquakes is southwest–northeast, whereas the possible fault plane of the strike-slip fault is from north-northwest to south-southeast, which is roughly perpendicular to the normal faults. Normal and strike-slip faults in the EF are of high dip angles, with the dip angles of the most faults ranging from 60° to 80°. Stress inversion results show that the major orientation of maximum horizontal stress (SHmax) is southwest–northeast, with minor local stress-field rotations. We further estimated earthquake energy release in the EF region using moment magnitude from the CMT solutions, and the cumulative earthquake energy release curve reveals three notable increases in cumulative seismic moment, which occurred in January–July 2018 and January–March 2019, and May–August 2019. Whether these energy releases were caused by anthropogenic activities is a matter for further investigation.

Seismicity and structure of the Kopet Dagh (Iran, U. S. S. R.)

1975 ◽  
Vol 278 (1275) ◽  
pp. 1-28 ◽  
Keyword(s):  
Active Surface ◽  
General Term ◽  
Fault System ◽  
The Caspian Sea ◽  
Tectonic Model ◽  
Longitudinal Zone ◽  
Kopet Dagh ◽  
And Migration ◽  
Tectonic Features ◽  
Northeast Iran

The region considered under the general term ‘Kopet Dagh’ is located east of the Caspian Sea, and includes Northeast Iran and southern Soviet Turkmenia. The regional tectonics are reviewed with special emphasis on the post-Alpine ‘Diagonal Fault System’. The seismicity over the last 100 years is studied, and the four strongest earthquakes in Northeast Iran, i.e. 1871/2, 1893 and 1895 Quchan and 1929 BaghanGermab, are described in detail for the first time on the basis of new bibliographical and field data. These four earthquakes were located on the NNW-SSE ‘Bakharden-Quchan Zone’, which forms part of the Diagonal Fault System. The 1929 earthquake in particular was accompanied by a surface fracture over 50 km long caused by reactivation of one of the faults of this Zone. Russian work on the seismotectonic aspects of the 1948 Ashkhabad earthquake which occurred in an adjoining zone, and migration of seismic activity in the Kopet Dagh since about 1870, are examined. The overall seismotectonics of the Kopet Dagh are interpreted in terms of an eastern ‘NNW trend’ which is separated by a longitudinal zone of relative quiescence near 56-57° E from a western ‘NNE trend’. Active surface structures throughout the region are on average consistent with a tectonic model based on a NNE motion of Iran with respect to the Turan Plate. Many tectonic features are characteristic of the margins of converging continental plates.

scholarly journals Rift kinematics preserved in deep-time erosional landscape below the northern North Sea

2021 ◽  
Author(s):  
Thilo Wrona ◽  
Alexander Whittaker ◽  
Rebecca Bell ◽  
Robert Gawthorpe ◽  
Haakon Fossen ◽  
...  
Keyword(s):  
North Sea ◽  
Drainage System ◽  
Normal Fault ◽  
Deep Time ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Stratigraphic Record ◽  
Continental Rifts ◽  
Northern North Sea ◽  
Stratigraphic Evolution

Our understanding of continental rifting is largely derived from the stratigraphic record. This archive is, however, incomplete as it does not capture the geomorphic and erosional record of rifting. New 3D seismic reflection data reveals a Late Permian-Early Triassic landscape incised into the pre-rift basement of the northern North Sea. This landscape, which covers at least 542 km2, preserves a drainage system bound by two major tectonic faults. A quantitative geomorphic analysis of the drainage system reveals 68 catchments, with channel steepness and knickpoint analysis of catchment-hosted paleo-rivers showing that the landscape preserved a >2 Myrs long period of transient tectonics. We interpret that this landscape records punctuated uplift of the footwall of a major rift-related normal fault at the onset of rifting. The landscape was preserved by a combination of relatively rapid subsidence in the hangingwall of a younger fault and burial by post-incision sediments. We show how and why erosional landscapes are preserved in the stratigraphic record, and how they can help us understand the tectono-stratigraphic evolution of ancient continental rifts.

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