Fault (geology)

About: Fault (geology) is a research topic. Over the lifetime, 26732 publications have been published within this topic receiving 744535 citations.

Structural Styles, Their Plate Tectonic Habitats, and Hydrocarbon Traps in Petroleum Provinces

Abstract: Broadly interrelated assemblages of geologic structures constitute the fundamental structural styles of petroleum provinces. These assemblages generally are repeated in regions of similar deformation, and their associated hydrocarbon traps can be anticipated prior to exploration. Styles are differentiated on the basis of basement involvement or detachment of sedimentary cover. Basement-involved styles include wrench-fault structural assemblages, compressive fault blocks and basement thrusts, extensional fault blocks, and warps. Detached styles are decollement thrust-fold assemblages, detached normal faults ("growth faults" and others), salt structures, and shale structures. These basic styles are related to the larger kinematics of plate tectonics and, in some situations, to particular depositional histories. Most styles have preferred plate-tectonic habitats: (1) wrench faults at transform and convergent plate boundaries; (2) compressive fault blocks and basement thrusts at convergent boundaries, particularly in forelands and orogenic belts; (3) extensional fault blocks at divergent boundaries in all stages of completion and certain parts of convergent boundaries; (4) basement warps in a variety of plate-interior and boundary settings; (5) decollement thrust-fold belts in trench inner walls and foreland zones of convergent boundaries; (6) detached normal faults, usually in unstable, thick clastic wedges (mostly deltas); (7) salt structures primarily in nterior grabens that may evolve to completed divergent boundaries; and (8) shale structures in regions with thick overpressured shale sequences. Important differences in trend arrangements and structural morphologies provide criteria for differentiation of styles. These differences also result in different kinds of hydrocarbon traps. Wrench-related structural assemblages are concentrated along throughgoing zones and many have en echelon arrangements. The basic hydrocarbon trap is the en echelon anticline, in places assisted by closure directly against the wrench fault itself. Compressive and extensional fault styles typically have multiple, repeated trends, which combine to form zigzag, dogleg, or other grid patterns. Their main trap types are fault closures and drape folds above the block boundaries. Basement warps (domes, arches, etc) are mostly solitary features and commonly provide long-lived positive areas for hydrocarbon concentration in broadly flexed closures. Most decollement thrust-fold structures are arranged in long, sinuous belts and are repeated in closely spaced, wavelike bands. Effective closures include slightly to moderately disrupted compressive anticlines and lead edges of thrust sheets. Most detached normal faults are listric faults that occur in coalescing, cuspate bands parallel with the strike of contemporaneous sedimentation. Their basic hydrocarbon traps are associated rollover anticlines which are uniquely concentrated along the downthrown sides of major faults. Salt and shale structures are present both as buoyantly rising pillows, domes, ridges, etc, and as highly complex injected features caused by tectonic forces. Stratigraphic factors, such as truncation, wedging, onlap, and unconformity, add to the variety of traps n all styles. In many places the structures of a petroleum province are either, or both, a gradation between the described fundamental styles and a mix of several styles. These structures can be further complicated by superimposition of fundamentally different tectonic environments. Additional modification of structures can result from still other factors inherent in the deformed region or in the particular tectonic event.

Origin and Development of the Philippine Sea

Abstract: The Central Basin Fault, an extinct mid-oceanic ridge, was probably connected by a long transform fault with the major ridge system (Kula-Pacific Ridge) which submerged under the Japanese and Kurile Arcs in late Cretaceous. When the direction of the motion of the Pacific plate changed from NNW to WNW during Eocene time, the Philippine ridge became extinct and WNW dipping subduction started at the transform fault which turned into an island arc. Then extensional openings of inter-arc basins followed to form basins to the east. The Kuyshu-Palau Ridge is probably the remnant of the old transform fault.

The relationship between Late Cenozoic tectonic events and stress field and basin development in northeast Japan

Abstract: The regional tectonic stress field, basin development, and crustal deformation of the NE Japan arc in the interval between 32 Ma to the Quaternary can be synthesized based on dike, vein, and fault orientation data, as well as on the compilation of the regional geology. An extensional stress field became prevalent from 32 Ma, and major normal faulting started at 25–20 Ma, which resulted from back arc rifting. Normal faulting, trending nearly parallel to the arc, propagated from the present Japan Sea coast to the forearc side, following the trenchward migration of the main volcanic field. From 20 to 15 Ma, normal faults with an oblique trend to the arc developed due to the counterclockwise rotation of NE Japan. The rapid clockwise rotation of SW Japan since 16 Ma produced a NW-SE directed transtensional stress regime in the NE Japan arc. Due to crustal stretching associated with this pull-apart movement, the back arc side of the NE Japan arc subsided rapidly to middle bathyal environments. After the termination of the opening of the Japan Sea at about 14 Ma, a neutral stress regime prevailed, which included phases of both weak extension and compression. Lithospheric cooling eventually led to thermal subsidence of the back arc region, and igneous underplating caused uplift of the axial zone of the volcanic arc. The increase in velocity of the westward motion of the Pacific plate at around 4 Ma produced strong compression across the arc, reactivating most of the Miocene normal faults, and uplifting the volcanic arc. The greatest crustal shortening occurred in areas that were stretched the most in the Miocene within the volcanic arc, which implies tectonic inversion.