scholarly journals Rifted margins: Ductile deformation, boudinage, continentward-dipping normal faults and the role of the weak lower crust

2018 ◽  
Vol 53 ◽  
pp. 20-40 ◽  
Author(s):  
Camille Clerc ◽  
Jean-Claude Ringenbach ◽  
Laurent Jolivet ◽  
Jean-François Ballard
Keyword(s):  
Lower Crust ◽  
Ductile Deformation ◽  
Normal Faults ◽  
Rifted Margins

scholarly journals The Role of Lower Crustal Rheology in Lithospheric Delamination During Orogeny

2021 ◽  
Vol 9 ◽  
Author(s):  
Lin Chen
Keyword(s):  
Lower Crust ◽  
Numerical Models ◽  
The Tibetan Plateau ◽  
Mantle Lithosphere ◽  
Laboratory Studies ◽  
Surface Uplift ◽  
Continental Lower Crust ◽  
Lower Crustal ◽  
Flow Laws

The continental lower crust is an important composition- and strength-jump layer in the lithosphere. Laboratory studies show its strength varies greatly due to a wide variety of composition. How the lower crust rheology influences the collisional orogeny remains poorly understood. Here I investigate the role of the lower crust rheology in the evolution of an orogen subject to horizontal shortening using 2D numerical models. A range of lower crustal flow laws from laboratory studies are tested to examine their effects on the styles of the accommodation of convergence. Three distinct styles are observed: 1) downwelling and subsequent delamination of orogen lithosphere mantle as a coherent slab; 2) localized thickening of orogen lithosphere; and 3) underthrusting of peripheral strong lithospheres below the orogen. Delamination occurs only if the orogen lower crust rheology is represented by the weak end-member of flow laws. The delamination is followed by partial melting of the lower crust and punctuated surface uplift confined to the orogen central region. For a moderately or extremely strong orogen lower crust, topography highs only develop on both sides of the orogen. In the Tibetan plateau, the crust has been doubly thickened but the underlying mantle lithosphere is highly heterogeneous. I suggest that the subvertical high-velocity mantle structures, as observed in southern and western Tibet, may exemplify localized delamination of the mantle lithosphere due to rheological weakening of the Tibetan lower crust.

scholarly journals The role of structural inheritance in the development of high-displacement crustal faults in the necking domain of rifted margins: The Klakk Fault Complex, Frøya High, offshore mid-Norway

2020 ◽  
Vol 140 ◽  
pp. 104163
Author(s):  
Jhon M. Muñoz-Barrera ◽  
Atle Rotevatn ◽  
Rob L. Gawthorpe ◽  
Gijs A. Henstra ◽  
Thomas B. Kristensen
Keyword(s):  
Structural Inheritance ◽  
Rifted Margins

Proterozoic extensional deformation in the Mount Isa inlier, Queensland, Australia

1989 ◽  
Vol 126 (1) ◽  
pp. 43-53 ◽  
Author(s):  
C. W. Passchier ◽  
P. R. Williams
Keyword(s):  
Ductile Deformation ◽  
Normal Faults ◽  
Extensional Deformation ◽  
Mount Isa ◽  
Lithospheric Extension ◽  
Extensional Faulting

AbstractThe earliest of four distinct phases of deformation recognized in the central part of the Proterozoic Mount Isa inlier involved brittle extensional faulting at shallow crustal levels. Extensional faulting produced stacks of imbricate fault slices, listric normal faults and characteristic tourmalinerich breccias. Structures belonging to this phase occur over a large part of the inlier and indicate an important phase of basin-forming crustal or lithospheric extension at 1750–1730 Ma. Late intense ductile deformation and tight folding of the imbricate systems destroyed part of these older structures, and obscures their existence in many parts of the inlier.

scholarly journals Dynamic slab segmentation due to brittle-ductile damage interactions in the outer rise

2020 ◽  
Author(s):  
Taras Gerya ◽  
David Bercovici ◽  
Thorsten Becker
Keyword(s):  
Plate Tectonics ◽  
Potential Temperature ◽  
Ductile Deformation ◽  
Ductile Damage ◽  
Normal Faults ◽  
Prior History ◽  
Outer Rise ◽  
Slab Breakoff ◽  
Subducting Plate ◽  
Oceanic Plates

Abstract The recycling of oceanic plates by means of subduction represents the major plate driving force and subducting plate strength controls many aspects of the thermo-chemical evolution of Earth. Regardless of its prior history, each subducting plate experiences intense normal faulting1-11 during bending that accommodates the transition from horizontal to downward motion at the outer rise at subduction trenches. Here, we investigate the consequences of this bending-induced plate damage using new numerical, thermomechanical subduction models in which both brittle and ductile deformation, as well as grain size evolution, are tracked and coupled self-consistently. Pervasive slab weakening and pronounced segmentation can occur at the outer rise region due to the strong feedback between brittle and ductile damage localization. The “memory” of bending varies from segmentation to broadly-distributed damage depending on the age of the subducting plate, mantle potential temperature, and the magnitude of strain-induced weakening of outer rise normal faults. This new slab damage phenomenon explains the development of large-offset normal faults8,9, the occurrence of deep compressional thrust-faulting earthquakes12, and the appearance of localized areas of reduced effective viscosity13 observed at subduction trenches. Furthermore, brittle-viscously damaged slabs show a strong tendency for slab breakoff at elevated mantle temperatures. Given Earth’s planetary cooling history14, this implies that intermittent subduction with frequent slab breakoff episodes15,16 may have been characteristic for terrestrial plate tectonics until more recent times than expected from memory-free rheologies17.

scholarly journals Superposition of two kinematically distinct extensional phases in southern Death Valley: Implications for extensional tectonics

Geosphere ◽  
2021 ◽  
Author(s):  
Z.D. Fleming ◽  
T.L. Pavlis ◽  
S. Canalda
Keyword(s):  
Early Period ◽  
Rock Avalanche ◽  
Strike Slip ◽  
Death Valley ◽  
Normal Faults ◽  
Geologic Mapping ◽  
The North ◽  
Transcurrent Deformation ◽  
Two Phases

Geologic mapping in southern Death Valley, California, demonstrates Mesozoic contractional structures overprinted by two phases of Neogene extension and contemporaneous strike-slip deformation. The Mesozoic folding is most evident in the middle unit of the Noonday Formation, and these folds are cut by a complex array of Neogene faults. The oldest identified Neogene faults primarily displace Neoproterozoic units as young as the Johnnie Formation. However, in the northernmost portion of the map area, they displace rocks as young as the Stirling Quartzite. Such faults are seen in the northern Ibex Hills and con­sist of currently low- to moderate-angle, E-NE– dipping normal faults, which are folded about a SW-NE–trending axis. We interpret these low-angle faults as the product of an early, NE-SW extension related to kinematically similar deformation recognized to the south of the study area. The folding of the faults postdates at least some of the extension, indicating a component of syn-exten­sional shortening that is probably strike-slip related. Approximately EW-striking sinistral faults are mapped in the northern Saddlepeak Hills. However, these faults are kinematically incompatible with the folding of the low-angle faults, suggesting that folding is related to the younger, NW-SE extension seen in the Death Valley region. Other faults in the map area include NW- and NE-striking, high-angle normal faults that crosscut the currently low-angle faults. Also, a major N-S–striking, oblique-slip fault bounds the eastern flank of the Ibex Hills with slickenlines showing rakes of <30°, which together with the map pattern, suggests dextral-oblique movement along the east front of the range. The exact timing of the normal faulting in the map area is hampered by the lack of geochronology in the region. However, based on the map relationships, we find that the older extensional phase predates an angular unconformity between a volcanic and/or sedimentary succession assumed to be 12–14 Ma based on correlations to dated rocks in the Owlshead Mountains and overlying rock-avalanche deposits with associated sedimentary rocks that we correlate to deposits in the Amargosa Chaos to the north, dated at 11–10 Ma. The mechanism behind the folding of the northern Ibex Hills, including the low- angle faults, is not entirely clear. However, transcurrent systems have been proposed to explain extension-parallel folding in many extensional terranes, and the geometry of the Ibex Hills is consistent with these models. Collectively, the field data support an old hypothesis by Troxel et al. (1992) that an early period of SW-NE extension is prominent in the southern Death Valley region. The younger NW-SE extension has been well documented just to the north in the Black Mountains, but the potential role of this earlier extension is unknown given the complexity of the younger deformation. In any case, the recognition of earlier SW-NE extension in the up-dip position of the Black Mountains detachment system indicates important questions remain on how that system should be reconstructed. Collectively, our observations provide insight into the stratigraphy of the Ibex Pass basin and its relationship to the extensional history of the region. It also highlights the role of transcurrent deformation in an area that has transitioned from extension to transtension.

scholarly journals Sealing assessment of normal faults in clastic reservoirs. The role of fault geometry and shale smear parameters.

2002 ◽  
Vol 67 (6) ◽  
pp. 576-589 ◽  
Author(s):  
Rasoul Sorkhabi ◽  
Shutaro Hasegawa ◽  
Shoji Iwanaga ◽  
Masamichi Fujimoto
Keyword(s):  
Normal Faults ◽  
Fault Geometry ◽  
Clastic Reservoirs
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