Flower structures in sandstones of the Paleozoic Inkisi Group (Brazzaville, Republic of Congo): evidence for two major strike-slip fault systems and geodynamic implications

2020 ◽  
Vol 123 (4) ◽  
pp. 531-550
Author(s):  
H.M.D-V. Nkodia ◽  
T. Miyouna ◽  
D. Delvaux ◽  
F. Boudzoumou
Keyword(s):  
Strike Slip ◽  
Strike Slip Fault ◽  
Fault System ◽  
Republic Of Congo ◽  
Fault Systems ◽  
Major Fault ◽  
Major Strike ◽  
Flower Structures ◽  
Dextral Strike Slip ◽  
East West

Abstract Few studies have reported field descriptions of flower structures associated with strike-slip faults. This study describes and illustrates flower structures near Brazzaville (Republic of Congo) and explains their implication for the tectonic history of the Paleozoic Inkisi Group. Field observations show that the Inkisi Group is affected by two major strike-slip fault systems. The oldest system is dominated by north-northwest–south-southeast striking sinistral strike-slip faults and minor east–west striking dextral strike-slip faults. The youngest system consists of dominant northeast–southwest striking dextral strike-slip faults and minor northwest–southeast striking sinistral strike-slip faults. Flower structures within these major strike slip faults show four types of arrangements that likely depend on fault growth, propagation and damage zones: (i) flower structures associated with wall damage zones; (ii) flower structures associated with linking damage zones; (iii) flower structures associated with tip damage zones; and (iv) “hourglass” flower structures. Paleostress analysis reveals that both major fault systems originated from two differently oriented pure strike-slip regime stress stages. The first stage, which engendered the first major fault system, developed under northwest–southeast compression (i.e, σ1 = 322°). This phase probably coincided with north–south collision in the southern part of Gondwana in the Permo-Triassic and the Late Cretaceous compression times. The second stress stage, creating the second major fault system, developed under east–west (i.e, σ1 = 078°) compression. This phase is correlated with compression from the east–west opening of the Atlantic Ocean in the Miocene times.

Integration of flower structures in strike-slip fault damage zones classification – examples from the West-Congo belt and foreland

2021 ◽  
Author(s):  
Hardy Medry Dieu-Veill Nkodia ◽  
Timothée Miyouna ◽  
Florent Boudzoumou ◽  
Damien Delvaux
Keyword(s):  
Cross Section ◽  
Democratic Republic Of Congo ◽  
Field Investigation ◽  
Strike Slip ◽  
Strike Slip Fault ◽  
The West ◽  
Republic Of Congo ◽  
Plan View ◽  
Flower Structures ◽  
Dextral Strike Slip

<p>Damage zones around strike-slip faults constitutes important site of earthquake initiation, propagation, rupture or barrier. They also constitute important sites that host and conduct fluids. Most investigations of these strike-slip damage zones focus on plan view geometries and little attention is paid to subsurface or profile geometries associated. Depending on the presence of a shortening or extensional component during deformation, strike-slip faults do not often show straight path in cross-section. Understanding the expression of damage zones in cross-section is therefore important in predicting subsurface strike-slip faults features. The Paleozoic red feldspathic sandstones of the Inkisi Group in the foreland of the West-Congo Belt show beautiful examples of strike-slip faults with damage zones in both the Republic of Congo and the Democratic Republic of Congo (Nkodia et al., 2020). These strike-slip faults are organized in two major faults system developed in a pure strike-slip regime. The oldest system is dominated by NNW–SSE trending sinistral strike-slip faults and minor E–W striking dextral strike-slip faults. The youngest system consists of dominant NE–SW trending dextral strike-slip faults and minor NW–SE trending sinistral strike-slip faults. Field investigation show four arrangement of flowers structures along the strike-slip faults: (i) those associated with wall damage zones; (ii) those associated with linking damage zones; (iii) those associated with tip damage zones; and (iv) “hourglass” flower structures. Further investigation of strike-slip faults in the Schisto-calaire Group of the West-Congo Belt show also similar flower structures arrangement in limestones. In the Inkisi Group, these arrangements are dependent on the fault growth and propagation. Both strike-slip faults system in the Inkisi Group show an evolving pattern, from closely spaced short faults segments, to highly spaced long faults segments with few interactions of pattern. </p><p>Nkodia, H.M.D.V., Miyouna, T., Delvaux, D., Boudzoumou, F., 2020. Flower structures in sandstones of the Paleozoic Inkisi Group (Brazzaville, Republic of Congo): evidence for two major strike-slip fault systems and geodynamic implications. South African Journal of Geology 123(4), 531-550. Doi: 10.25131/sajg.123.0038.</p>

Dextral strike-slip faulting in the Cariboo Mountains, British Columbia: a natural example of wrench tectonics in relation to Cordilleran tectonics

2002 ◽  
Vol 39 (6) ◽  
pp. 953-970 ◽  
Author(s):  
L F Reid ◽  
P S Simony ◽  
G M Ross
Keyword(s):  
British Columbia ◽  
Rocky Mountain ◽  
Strike Slip ◽  
Strike Slip Fault ◽  
Fault System ◽  
Fault Systems ◽  
Dextral Strike Slip Fault ◽  
Deformation Event ◽  
Step Over ◽  
Dextral Strike Slip

The Cariboo Mountains, British Columbia, contain an intracontinental dextral strike-slip fault system that crosscuts the regional fold structures. This fault system accounts for a minimum of 120 km and a maximum of 200 km of dextral strike-slip displacement. This probably accommodates some of the motion associated with the southern termination of the Northern Rocky Mountain Trench Fault and is part of a step-over zone between the Northern Rocky Mountain Trench Fault and the Fraser River – Straight Creek fault systems. The Isaac Lake Synclinorium is a kilometre-scale Jurassic fold structure that is bounded by the dextral oblique Isaac Lake and Winder strike-slip faults. These faults are part of the regional strike-slip fault system that is found throughout the Cariboo Mountains. Deformation associated with the strike-slip faults is complex and is partitioned into motion along the faults and into the formation of kilometre-scale folds that are found in areas between the faults. The angular relationship between the strike-slip faults and folds conforms to models developed for dextral strike-slip fault systems with drag on high-friction faults. We interpreted these structures to have formed during a continuous deformation event. Timing constraints indicate that faulting started by the Late Cretaceous and may have had a long and protracted history into the Tertiary.

scholarly journals First evidence of active transpressive surface faulting at the front of the eastern Southern Alps, northeastern Italy. Insight on the 1511 earthquake seismotectonics

2018 ◽  
Author(s):  
Emanuela Falcucci ◽  
Maria Eliana Poli ◽  
Fabrizio Galadini ◽  
Giancarlo Scardia ◽  
Giovanni Paiero ◽  
...  
Keyword(s):  
Strike Slip ◽  
Southern Alps ◽  
Strike Slip Fault ◽  
Fault System ◽  
The Past ◽  
Fold And Thrust Belt ◽  
Northeastern Italy ◽  
Dextral Strike Slip Fault ◽  
Seismic Lines ◽  
Dextral Strike Slip

Abstract. We investigated the eastern corner of northeastern Italy, where the NW-SE trending dextral strike-slip fault systems of western Slovenia intersects the south-verging fold and thrust belt of the eastern Southern Alps . The area suffered the largest earthquakes of the region, among which are the 1511 (Mw 6.3) event and the two major shocks of the 1976 seismic sequence, with Mw = 6.4 and 6.1 respectively. The Colle Villano thrust and the Borgo Faris-Cividale strike-slip fault have been first analyzed by interpreting industrial seismic lines and then by performing morpho-tectonic and paleoseismological analyses. These different datasets indicate that the two structures define an active, coherent transpressive fault system that activated twice in the past two millennia, with the last event occurring around the 15th–17th century. The chronological information, and the location of the investigated fault system suggest its activation during the 1511 earthquake.

scholarly journals Pull-apart basin tectonic model is structurally impossible for Kashmir basin, NW Himalaya

2016 ◽  
Author(s):  
A. A. Shah
Keyword(s):  
Strike Slip ◽  
Strike Slip Fault ◽  
Fault System ◽  
Nw Himalaya ◽  
Tectonic Model ◽  
Pull Apart Basin ◽  
Piggyback Basin ◽  
Kashmir Basin ◽  
Dextral Strike Slip Fault ◽  
Dextral Strike Slip

Abstract. Kashmir Basin in NW Himalaya is considered a Neogene-Quatermary piggyback basin that was formed as result of the continent-continent collision of Indian and Eurasian plates. This model however is recently challenged by a pull-apart basin model, which argues that a major dextral strike-slip fault through Kashmir basin is responsible for its formation. And here it is demonstrated that the new tectonic model is structurally problematic, and conflicts with the geomorphology, geology, and tectonic setting of Kashmir basin. It also conflicts, and contradicts with the various structural features associated with a typical dextral strike-slip fault system where it shows that such a major structure cannot pass through the middle of the basin. It is demonstrated that such a structure is structurally, and kinematically impossible, and could not exist.

Linking dynamic earthquake rupture to tsunami modeling for the Húsavík-Flatey transform fault system in North Iceland

2021 ◽  
Author(s):  
Fabian Kutschera ◽  
Sara Aniko Wirp ◽  
Bo Li ◽  
Alice-Agnes Gabriel ◽  
Benedikt Halldórsson ◽  
...  
Keyword(s):  
Strike Slip ◽  
Strike Slip Fault ◽  
Fault System ◽  
Deformation Pattern ◽  
Tsunami Modeling ◽  
Earthquake Rupture ◽  
Worst Case ◽  
Fault Systems ◽  
Complex Fault ◽  
The Impact

<p>Earthquake generated tsunamis are generally associated with large submarine events on dip-slip faults, in particular on subduction zone megathrusts (Bilek and Lay, 2018). Submerged ruptures across strike-slip fault systems mostly produce minor vertical offset and hence no significant disturbance of the water column. For the 2018 Mw 7.5 Sulawesi earthquake in Indonesia, linked dynamic earthquake rupture and tsunami modeling implies that coseismic, mixed strike-slip and normal faulting induced seafloor displacements were a critical component generating an unexpected and devastating local tsunami in Palu Bay (Ulrich et al., 2019), with important implications for tsunami hazard assessment of submarine strike-slip fault systems in transtensional tectonic settings worldwide. </p><p>We reassess the tsunami potential of the ~100 km Húsavík Flatey Fault (HFF) in North Iceland using physics-based, linked earthquake-tsunami modelling. The HFF consists of multiple fault segments that localise both strike-slip and normal movements, agreeing with a transtensional deformation pattern (Garcia and Dhont, 2005). The HFF hosted several historical earthquakes with M>6. It crosses from off-shore to on-shore in immediate proximity to the town of Húsavík. We analyse simple and complex fault geometries and varying hypocenter locations accounting for newly inferred fault geometries (Einarsson et al., 2019), 3-D subsurface structure (Abril et al., 2020), bathymetry and topography of the area, primary stress orientations and the stress shape ratio constrained by the inversion of earthquake focal mechanisms (Ziegler et al., 2016).</p><p>Dynamic rupture models are simulated with SeisSol (https://github.com/SeisSol/SeisSol), a scientific open-source software for 3D dynamic earthquake rupture simulation (www.seissol.org, Pelties et al., 2014). SeisSol, a flagship code of the ChEESE project (https://cheese-coe.eu), enables us to explore simple and complex fault and subsurface geometries by using unstructured tetrahedral meshes. The dynamically adaptive, parallel software sam(oa)²-flash (https://gitlab.lrz.de/samoa/samoa) is used for tsunami propagation and inundation simulations and solves the hydrostatic shallow water equations (Meister, 2016). We consider the contribution of the horizontal ground deformation of realistic bathymetry to the vertical displacement following Tanioka and Satake, 1996. The tsunami simulations use time-dependent seafloor displacements to initialise bathymetry perturbations. </p><p>We show that up to 2 m of vertical coseismic offset can be generated during dynamic earthquake rupture scenarios across the HFF, which resemble historic magnitudes and are controlled by spontaneous fault interaction in terms of dynamic and static stress transfer and rupture jumping across the complex fault network. Our models reveal rake deviations from pure right-lateral strike-slip motion, indicating the presence of dip-slip components, in combination with large shallow fault slip (~8 m for a hypocenter in the East), which can cause a sizable tsunami affecting North Iceland. Sea surface height (ssh), which is defined as the deviation from the mean sea level, and inundation synthetics give an estimate about the impact of the tsunami along the coastline. We further investigate a physically plausible worst-case scenario of a tsunamigenic HFF event, accounting for tsunami sourcing mechanisms similar to the one causing the Sulawesi Tsunami in 2018.</p>

scholarly journals Late Quaternary slip rates for faults of the central Walker Lane (Nevada, USA): Spatiotemporal strain release in a strike-slip fault system

Geosphere ◽  
2019 ◽  
Vol 15 (5) ◽  
pp. 1460-1478 ◽  
Author(s):  
Stephen J. Angster ◽  
Steven G. Wesnousky ◽  
Paula M. Figueiredo ◽  
Lewis A. Owen ◽  
Sarah J. Hammer
Keyword(s):  
Late Pleistocene ◽  
Strike Slip ◽  
Strike Slip Fault ◽  
Luminescence Dating ◽  
Slip Distribution ◽  
Fault System ◽  
Slip Rates ◽  
Walker Lane ◽  
Fault Systems ◽  
Late Pleistocene To Holocene

Abstract The Walker Lane is a broad shear zone that accommodates a significant portion of North American–Pacific plate relative transform motion through a complex of fault systems and block rotations. Analysis of digital elevation models, constructed from both lidar data and structure-from-motion modeling of unmanned aerial vehicle photography, in conjunction with 10Be and 36Cl cosmogenic and optically stimulated luminescence dating define new Late Pleistocene to Holocene minimum strike-slip rates for the Benton Springs (1.5 ± 0.2 mm/yr), Petrified Springs (0.7 ± 0.1 mm/yr), Gumdrop Hills (0.9 +0.3/−0.2 mm/yr), and Indian Head (0.8 ± 0.1 mm/yr) faults of the central Walker Lane (Nevada, USA). Regional mapping of the fault traces within Quaternary deposits further show that the Indian Head and southern Benton Springs faults have had multiple Holocene ruptures, with inferred coseismic displacements of ∼3 m, while absence of displaced Holocene deposits along the Agai Pah, Gumdrop Hills, northern Benton Springs, and Petrified Springs faults suggest they have not. Combining these observations and comparing them with geodetic estimates of deformation across the central Walker Lane, indicates that at least one-third of the ∼8 mm/yr geodetic deformation budget has been focused across strike-slip faults, accommodated by only two of the five faults discussed here, during the Holocene, and possibly half from all the strike-slip faults during the Late Pleistocene. These results indicate secular variations of slip distribution and irregular recurrence intervals amongst the system of strike-slip faults. This makes the geodetic assessment of fault slip rates and return times of earthquakes on closely spaced strike-slip fault systems challenging. Moreover, it highlights the importance of understanding temporal variations of slip distribution within fault systems when comparing geologic and geodetic rates. Finally, the study provides examples of the importance and value in using observations of soil development in assessing the veracity of surface exposure ages determined with terrestrial cosmogenic nuclide analysis.

Sign in / Sign up

Export Citation Format

Share Document