Strike-slip Transfer Fault Research Articles

Late Cenozoic Clockwise Rotations in the Westernmost Part of the Arcuate Qiulitage Fold‐and‐Thrust Belt of Southern Tian Shan Foreland and Its Tectonic Implications

AbstractCurvature of fold‐and‐thrust belts (FTBs) is a rather common feature in foreland basins. The problem of how curves in FTBs originate is essential for understanding the propagation of deformation and tectonic history of orogens. In this study, we carried out systematic paleomagnetic studies in the westernmost part of the Qiulitage FTB, southern Tian Shan foreland, where thrusting, strike‐slip fault, and tectonic boundary coexist. Our new results suggest that the study area has been subjected to ~20° clockwise rotations after ~5 Ma. Oroclinal test of the paleomagnetic data across the FTB suggests that oroclinal bending caused by the formation of the curved Qiulitage FTB is the dominate reason for these tectonic rotations. The Kalayuergun dextral strike‐slip transfer fault delimiting the western boundary of the Qiulitage FTB is a thin‐skinned structure accommodating the discrepancy in horizontal displacement on both sides of it. These results also suggest that the formation of the curved Qiulitage FTB should not be older than ~5 Ma, indicating that the southern Tian Shan foreland has experienced significant tectonic shortening since the latest Miocene to early Pliocene. Our new results, together with previous studies on deformation history, estimates of crustal shortening, GPS observations and earthquake records, suggest that the southern Tian Shan foreland has been subjected to significant deformation during the past ~5 million years, and the crustal shortening is still ongoing.

Hydrothermal dolomite reservoir in the Precambrian Dengying Formation of central Sichuan Basin, Southwestern China

The Precambrian Dengying Formation is maximum buried carbonate reservoir in the Sichuan Basin. Reservoir types are thought to be dominated by sedimentary facies or karst controlled. Precursory sedimentary fabrics have been intensively superimposed by medium-to coarse-grained dolomite in most areas. Dolomitized intervals contain planar and saddle dolomite, quartz, and few hydrothermal replacive minerals. Fluid inclusion analyses of dolomite suggests that rocks are formed at temperatures ranging from 132.6°C to 218.7°C in the presence of dense brines, while the dolomite phases are demonstrated by negative δ18O and δ13C VPDB values. Strontium isotopes enriched in 87Sr, and the fluid source could support the conclusion. The dolomites of the Dengying Formation in central Sichuan Basin that formed around basement-rooted wrench faults, in turn mainly oriented towards the North-South and East-West strike-slip faults, are detectable. Lastly, the grabens take the form of negative flower structures-the result of an intra-cratonic rift that took place during the Sinian and early Cambrian period through tensional faulting.Our primary contention is that basement fault, which resulted in the magmatic or deep clastic fluids migration, was key for the formation of the obvious high-temperature coarse dolomite and saddle dolomite replacement. Subsequently, hot fluids that circulated within the matrix dolomite were aided by fractures or vugs and (1) leached into the dolomite, producing vugs and pores; (2) precipitated saddle dolomite, and (3) led to hydrofracturing, fractures enlargement, and further brecciation. The dolomite eventually formed porous hydrocarbon reservoirs through diagenesis. This model better illustrates how fluids that originated from deep basin migration along strike-slip transfer faults and fractures flowed out to structures in Precambrian basement-rooted faults, inheriting the rift in the Cambrian. The data involved offers a fresh perspective pertinent to deep hydrocarbon exploration of dolomite reservoirs in Southwestern China.

The Morphotectonic units of Ikaria island – Contribution in the natural hazards research

Present morphological and tectonic image of Ikaria island is the complex result of both the tem-poral evolution of the island, as part of the geodynamical evolution of the Hellenic Arc, especially that of the last stages (from the upper Miocene and after), and the exogenous factors. Also human impact functions as an additional parameter for the formation of Ikaria geoenvironment.According to field data and their analysis, computing and estimation which took part with the use of modern technologies (use of GIS, analysis of geographical and descriptive databases) the mor-photectonic units of Ikaria Island were defined. The definition of the morphotectonic units was based on their special features and more precisely on the lithological differentiation (granite, metamorphic rocks and post alpine formations) as well as the complex ductile and brittle structures (large scale ductile shear-zones and brittle detachment faults, normal faults, strike-slip transfer faults and join sets) and the morphological features (slope distribution, asymmetry of the drainage system, planation surfaces, morphological discontinuities etc).The synthesis of the special features of each morphotectonic unit in combination with the human impact (fires, overgrazing etc), defines the kind, the intensity and the geographical localization of the natural hazards which occur in various sites of the island, such as landslides, erosion, floods, seismic activity, relief changes, coastline changes etc.

Slab rupture and delamination under the Betics and Rif constrained from receiver functions

We map the lithospheric structure under the westernmost Mediterranean convergent setting interpreting P-receiver functions obtained from a dense seismic network. No orogenic root occurs under the eastern and great part of the central Betics. However, the subducted South Iberian continental lithosphere is found beneath the western Betics where the Iberian Moho reaches depths of approximately 65km, dipping gently towards the SE. Meanwhile, at the Rif, strong crustal and lithospheric thickness contrasts occur across the Nekor NW-SE sinistral fault that overlies the region of present slab tearing. East of the Nekor fault there is no orogenic root and the crust has been thinned to approximately 22km, whilst to the west the crust reaches 55km thickness and the Maghrebian continental lithosphere is attached to the lithospheric slab imaged by tomography under the Alboran basin. These data suggest that subduction rollback under the Alboran and Algerian basins, together with continental slab tearing or detachment producing edge delamination under the Betics and Rif have been the main tectonic mechanisms driving extension, magmatism and regional uplift in the westernmost Mediterranean since the Late Miocene until present. The surface expression of edge-delamination and slab tearing is marked by regional uplift, denudation of HP rocks in elongated core-complex type domes, late Miocene volcanism in the Eastern Betics and Rif, and by large NE-SW strike-slip transfer faults like the Alpujarras, Crevillente, Torcal or Nekor faults that accommodate strong gradients in crustal displacements. The Iberian slab is still attached to the oceanic slab imaged under the Alboran basin at the western Betics where intermediate depth seismicity, recent dextral strike-slip faulting and folding, could reflect slab tearing. Meanwhile, active faulting and differential GPS-measured displacements would mark slab tearing beneath the Rif coinciding with the trace of the sinistral Nekor fault.

Near-surface imaging of a hydrogeothermal system at Mount Princeton, Colorado using 3D seismic, self-potential, and dc resistivity data

The Upper Arkansas Valley in the Rocky Mountains of central Colorado is the northernmost extensional basin of the Rio Grande Rift (Figure 1). The valley is a half graben bordered to the east and west by the Mosquito and Sawatch ranges, respectively. The Sawatch Range is home to the Collegiate Peaks, which include some of the highest summits in the Rocky Mountains. Some Collegiate Peaks over 4250 m (14,000 ft) from north to south include Mount Harvard, Mount Yale, Mount Princeton, and Mount Antero. The Sawatch range-front normal fault strikes north-northwest along the eastern margin of the Collegiate Peaks and is characterized by a right-lateral offset between the Mount Princeton batholith and Mount Antero. This offset in basin-bounding faults is accommodated by a northeast-southwest dextral strike-slip transfer fault (Richards et al., 2010) and coincides with an area of hydrogeothermal activity and Mount Princeton Hot Springs. This transfer fault is here termed the Chalk Creek fault due to it's alignment with the Chalk Creek valley. A 250-m high erosional scarp, called the Chalk Cliffs, lies along the northern boundary of this valley. The cliffs are geothermally altered quartz monzonite and not chalk. These cliffs coincide with the Chalk Creek fault, whose intersection with the Sawatch range-front normal fault results in a primary pathway for upwelling geothermal waters.

Active transfer fault zone linking a segmented extensional system (Betics, southern Spain): Insight into heterogeneous extension driven by edge delamination

Pliocene and Quaternary tectonic structures mainly consisting of segmented northwest–southeast normal faults, and associated seismicity in the central Betics do not agree with the transpressive tectonic nature of the Africa–Eurasia plate boundary in the Ibero-Maghrebian region. Active extensional deformation here is heterogeneous, individual segmented normal faults being linked by relay ramps and transfer faults, including oblique-slip and both dextral and sinistral strike-slip faults. Normal faults extend the hanging wall of an extensional detachment that is the active segment of a complex system of successive WSW-directed extensional detachments which have thinned the Betic upper crust since middle Miocene. Two areas, which are connected by an active 40-km long dextral strike-slip transfer fault zone, concentrate present-day extension. Both the seismicity distribution and focal mechanisms agree with the position and regime of the observed faults. The activity of the transfer zone during middle Miocene to present implies a mode of extension which must have remained substantially the same over the entire period. Thus, the mechanisms driving extension should still be operating. Both the westward migration of the extensional loci and the high asymmetry of the extensional systems can be related to edge delamination below the south Iberian margin coupled with roll-back under the Alborán Sea; involving the asymmetric westward inflow of asthenospheric material under the margins.

Lateral interaction between metamorphic core complexes and less-extended, tilt-block domains: the Alpujarras strike-slip transfer fault zone (Betics, SE Spain)

The Alpujarras area in southeastern Spain exhibits one of the scant documented examples of extension related strike-slip faults bordering core complexes in the world. Faults of the Alpujarras fault zone define a regional-scale complex ENE-striking transfer zone that marks the boundary among the Sierra Nevada elongated dome, a highly-extended, constricted core-complex, and a less-extended domain formed by large-scale tilt-blocks. Detailed mapping and structural analysis show that the Alpujarras fault zone is an integral part of the WSW-directed normal fault systems that thinned the Betic hinterland during the middle Miocene to Recent time. Fault patterns and palaeostress analysis both indicate that dextral movement along the strike-slip faults was induced by a local stress field with a sub-horizontal E–W- to ESE–WNW-trending maximum principal stress axis, which is synchronous with the regional stress field driving the normal fault systems. Palaeostress analysis also indicates subsequent variations in the stress field with a sub-horizontal NW–SE- to N–S-trending maximum principal stress axis, thus producing both the tectonic inversion of the northern fault of the Alpujarras system and shortening of the unloaded extensional detachment footwall. A simplified kinematic model for the tectonic evolution of the Alpujarras area from the middle Miocene to Recent emphasizes the kinematic coupling of normal faults and strike-slip transfer zones in the extensional process.

Structure and Mechanics of the Hayward-Rodgers Creek Fault Step-Over, San Francisco Bay, California

A dilatational step-over between the right-lateral Hayward and Rodgers Creek faults lies beneath San Pablo Bay in the San Francisco Bay area. A key seismic hazard issue is whether an earthquake on one of the faults could rupture through the step-over, enhancing its maximum possible magnitude. If ruptures are terminated at the step-over, then another important issue is how strain transfers through the step. We developed a combined seismic reflection and refraction cross section across south San Pablo Bay and found that the Hayward and Rodgers Creek faults converge to within 4 km of one another near the surface, about 2 km closer than previously thought. Interpretation of potential field data from San Pablo Bay indicated a low likelihood of strike-slip transfer faults connecting the Hayward and Rodgers Creek faults. Numerical simulations suggest that it is possible for a rupture to jump across a 4-km fault gap, although special stressing conditions are probably required (e.g., Harris and Day, 1993, 1999). Slip on the Hayward and Rodgers Creek faults is building an extensional pull-apart basin that could contain hazardous normal faults. We investigated strain in the pull-apart using a finite-element model and calculated a � 0.02-MPa/yr differential stressing rate in the step-over on a least-principal-stress orientation nearly parallel to the strike-slip faults where they overlap. A 1- to 10- MPa stress-drop extensional earthquake is expected on normal faults oriented per- pendicular to the strike-slip faults every 50-500 years. The last such earthquake might have been the 1898 M 6.0-6.5 shock in San Pablo Bay that apparently pro- duced a small tsunami. Historical hydrographic surveys gathered before and after 1898 indicate abnormal subsidence of the bay floor within the step-over, possibly related to the earthquake. We used a hydrodynamic model to show that a dip-slip mechanism in north San Pablo Bay is the most likely 1898 rupture scenario to have caused the tsunami. While we find no strike-slip transfer fault between the Hayward and Rodgers Creek faults, a normal-fault link could enable through-going segmented rupture of both strike-slip faults and may pose an independent hazard of M � 6 earthquakes like the 1898 event.

The past of a future syntaxis across the Zagros

Abstract Longitudinal components of the Zagros mountain chain change in character and width across N-S trending zones of strike-slip transfer faults lying between 51° and 54°E. To the northwest, a fold-thrust belt with consistent SW vergence has a width of c. 220 km in front of an imbricate belt c. 160 km wide. To the southeast, an imbricate zone c. 80 km wide is fronted by a gently tapering festoon of upright periclines that is c. 350 km wide and punctured by over a hundred emergent salt diapirs. Pre-Zagros stages of the transfer zones in the Zagros are preserved on the Arabian platform and the two most obvious bound what we call the incipient Qatar syntaxis. This is at an early stage of one of the many syntaxes that compartmentalize the Alpine-Himalayan mountain chain. We use structures in the Hormuz salt to map and gauge the tectonic pulse of basement blocks that jostled as ocean basins opened and closed diachronously like zip fasteners along the Tethyan margin of Gondwana. This incipient syntaxis was a lithospheric key that went up while others went down during the rifting and riffling, but not drifting, of the still-born Hormuz basin we call Proto-Tethys.

Neogene lateral extension during convergence in the Central Alps: Evidence from interrelated faulting and backfolding around the Simplonpass (Switzerland)

The Simplon Fault Zone occurs at the western end of the Lepontine metamorphic dome in the Central Alps and represents a major, low-angle (25° dip) normal fault associated with WSW-ENE-directed lateral extension. Movement began in the early Miocene and continued until at least 3 Ma, accumulating a total vertical throw of around 10 km, corresponding to 24 km displacement parallel to the fault. This displacement is partitioned between a broad zone of ductile mylonites in the footwall and a more discrete cataclastic “detachment fault” (the Simplon Line). In the central region (Simplon village to Zwischbergen), some 3 km of the total vertical displacement is accommodated by the discrete cataclastic zone. Due to the higher exposed structural level, the importance of the cataclastic component increases towards the northwest. In the northern “steep belt” around the Simplonpass, retrograde greenschist-facies mylonite formation and younger cataclastic faulting associated with lateral extension occurred contemporaneously with SSE-vergent, large-scale backfolding, representing NNW-SSE shortening and crustal thickening. The combined effect was an overall shortening across the orogen accommodated by an extension parallel to the orogen, allowing lateral escape of continental material. Normal faulting and the resultant lateral escape was not just superficial. It extended to depths of at least 15 km, and probably to depths exceeding 25 km. The overall geometry and kinematics of the Simplon Fault Zone, and in particular the interplay between folding and faulting, is very similar to that described from the metamorphic core complexes and detachment faults of the Cordillera of the southwestern USA. Within the Central Alps, extension was associated with rapid exhumation of the Lepontine metamorphic dome, as evidenced by very rapid cooling rates determined from mineral ages in the footwall. Similar to the Cenozoic tectonics of the Himalayas and Tibet, orogen-parallel extension in the mountain belt may have been promoted by an overall reduction in the horizontal compressive stress in this direction. More limited extension of the same age and orientation is known from a large area of the European foreland. Greater extension in the mountain belt compared with the foreland was accommodated by major strike-slip transfer fault systems and was linked to coeval overthrusting of the lowlands towards the southwest in the external southwestern Alps of Haute Provence (France). Coeval folding and orogen-parallel extension, such as at the Simplonpass, were developed in a dextral transpressive regime due to oblique WNW-ESE convergence across the Alps during the Neogene.