Growth processes and melange formation in the southern Apennines accretionary wedge
173
Citation
26
Reference
10
Related Paper
Citation Trend
Keywords:
Accretionary wedge
Thrust fault
Décollement
continental collision
Focal mechanism
Thrust fault
Accretionary wedge
Collision zone
Cite
Citations (22)
Small-scale stratal extension is commonly associated with thrust faults in the Makran accretionary prism of southwest Pakistan. Low-angle normal faults, dipping in the direction of transport relative to the thrust, are common in gouge zones and duplexes, and may also cut the and hanging wall, where they cause stratal extension. These faults are probably Riedel shears. We have studied a broad zone of more complex extensional deformation beneath one bedding-parallel thrust. The zone disrupts earlier compressional structures and affects a significant volume of the footwall. Normal faults, initiating in a rearward sequence, branch off the thrust and cut down into the footwall, merging at a lower stratigraphic level. Part of the thrust displacement was thereby transfe red to that level, and fragments of the were detached and transferred southward beneath the hanging wall. The latter remained undeformed, and accommodation structures are confined to the footwall. These effects may have been caused by variations in sliding resistance along the fault. If a thrust transfers part or all of its displacement down section along normal faults in this way, before eventually cutting back up toward the surface, it will detach a rootless fragment of rocks from a position forward of the initial ramp through that horizon. This process can be referred to as footwall plucking. It can explain rootless basement slices along thrusts, for example, and it has important implications for section restoration techniques and the interpretation of thrust belts.
Accretionary wedge
Prism
Thrust fault
Cite
Citations (65)
Décollement
Thrust fault
Devonian
Accretionary wedge
Extensional fault
Cite
Citations (27)
Accretionary wedge
Thrust fault
Décollement
Cite
Citations (173)
An interpretation of the deep structure of the continental shelf offshore southern Vancouver Island, subject to constraints from other geophysical data, is derived by combining seismic reflection profiles shot in 1989 with those from an earlier 1985 survey. Accretionary wedge sediments, which extend landward beneath the volcanic Crescent terrane, comprise two primary units, both of which have shortened through duplex formation. The maximum thickness of the Crescent terrane, 6–8 km, occurs just seaward of its contact with the inboard, largely metasedimentary Pacific Rim terrane. The E region of reflectivity, first detected dipping landward beneath Vancouver Island, is regionally extensive, being observed on all the seismic profiles. The E reflectivity thins seaward and splits into two or more strands that probably link into major faults within the accreted sedimentary wedge. Reflections from the interplate décollement beneath the outer continental shelf separate from the downgoing plate, continue into the deepest level of the E reflectivity, and are interpreted to represent a single décollement surface above which imbrication of accreted units occurred. It is proposed that at the southern end of Vancouver Island the E reflections represent mainly underthrust sediments above a former subduction décollement, both of which were incorporated into the overlying continent when the subduction thrust stepped down into the descending oceanic plate. This change in depth of the subduction thrust underplated one or more mafic units to the continent. The reflection from the top of the subducting Juan de Fuca plate appears to be around 5 km shallower farther north along the margin, indicating that the underplated region could be confined to the embayment in the Cascadia subduction zone.
Accretionary wedge
Imbrication
Underplating
Décollement
Continental Margin
Volcanic arc
Thrust fault
Cite
Citations (37)
This study focuses on structure and kinematics of the 1979 Mw 7.1 Montenegro earthquake. Although this event represents the strongest instrumentally recorded event in the entire Dinarides-Hellenides fold-and-thrust belt, no tectonic model relating this event to any particular fault existed so far. We combined onshore geological information with well logs, seismic lines, bathymetric data, seismotectonic and seismological data as well as cross-section balancing techniques into a new structural model for the area. Our results suggest that main shock and strongest aftershock (Mw 6.2) occurred on the NE-dipping basal thrust of a largely Palaeogene-age nappe system involving Cretaceous neritic carbonates. Ongoing propagation of this thrust system is documented by the existence of elongated ridges located 15 km offshore. Reflection seismic and bathymetry data reveal that the ridges form crests of actively growing fault-related anticlines. Slip distribution models of the strongest events imply that the basal thrust below the ridges accommodated up to 2.7 m of coseismic displacement. Ongoing shortening along the basal thrust also induced surface uplift of structurally higher thrust imbricates, evidenced by dry valleys incising onshore anticline crests. Combining all evidence, we speculate that the observed structural and geomorphic features resulted from repeated seismogenic faulting events as in 1979.
Anticline
Thrust fault
Cite
Citations (30)
Accretionary wedge
Wedge (geometry)
Neogene
Strain partitioning
Thrust fault
Décollement
Echelon formation
Cite
Citations (15)
Accretionary wedge
Seafloor Spreading
Thrust fault
Cite
Citations (96)
Accretionary wedge
Cite
Citations (28)
Accretionary wedge
Décollement
Wedge (geometry)
Thrust fault
Cite
Citations (31)