14. Wrench Tectonics - Supplements
Contents
Terminology of Wrench Tectonics
Flower structureAn array of faults in a strike-slip fault zone that merges at depth into a near-vertical fault plane, but near the ground surface diverges so as to have shallower dips. In a positive flower structure, there is a component of thrusting on the faults, and in a negative flower structure, there is a component of normal faulting.
Horsetail A group of fault splays at the endpoint (fault tip) of a fault; the splays diverge to define a fanlike array in map view.
Lateral escape The strike-slip movement of a crustal block in a direction perpendicular to the regional convergence direction in a collisional orogen; the block is essentially squeezed laterally out of the way of the colliding blocks.
Lateral ramp A surface connecting two non-coplanar parts of a thrust fault or normal fault (i.e., a ramp that is roughly parallel to the transport direction). Strike-slip movement occurs on a lateral ramp.
Non-coplanar An adjective used to describe a geometric arrangement of two planes in which the planes have the same attitude, but are not aligned end-to-end to form a single plane.
Pull-apart basin A sedimentary basin that forms at a releasing bend along a strike-slip fault.
Releasing bend In the context of describing a strike-slip fault, it is a map-view bend, in the fault plane, whose orientation is such that the block on one side of the fault pulls away from the block on the other, causing transtensional deformation.
Restraining bendIn the context of describing a strike-slip fault, it is a map-view bend, in the fault plane, whose orientation is such that the block on one side of the fault pushes against the block on the other, causing transpressional deformation.
Stepover A geometry that occurs where the end of one fault trace overlaps the end of another, non-coplanar fault trace.
Strike-slip duplexAn arrangement of sigmoidal-shaped fault splays (in map view) at a stepover, a restraining bend, or a releasing bend, whose geometry in map view resembles the cross-sectional geometry of the duplexes that occur in thrust-fault or normal-fault systems.
Strike-slip faultAny fault on which displacement vectors are parallel to the strike of the fault, in present-day surface coordinates. The use of this term is purely geometric, and has no genetic, tectonic, or size connotation.
Tear fault A traditional term for strike-slip faults that occur in a thrust sheet and accommodate differential displacement of one part of a thrust sheet relative to an adjacent part; in more recent jargon, a tear fault is a vertical lateral ramp.
Transcurrent faultA strike-slip fault that has the following characteristics: it dies out along its length; the displacement across it is less than the length of the fault; the length of the fault increases with time and continued movement; displacement on the fault is greatest at the center of the fault trace and decreases toward the endpoints (tips) of the fault.
Transfer faultA strike-slip fault that has the following characteristics: once formed, displacement across it can be constant along the length of the fault; displacement across it can be much greater than the length of the active fault; its length can be constant, increase, or decrease with time; it terminates at another fault. Transform faults can be lithosphere plate boundaries, in which case they terminate at intersections with other plate boundaries.
Transform faultA transfer fault that marks a plate boundary; both oceanic and continental transforms occur.
Transpression A combination of strike-slip and compressional deformation; transpression occurs where a fault is not parallel to the map projection of regional displacement vectors, so that there is a component of compression across the fault (leading to shortening).
Transtension A combination of strike-slip and tension; transtension occurs where a fault is not parallel to the map projection of regional displacement vectors, so that there is a component of tension across the fault (leading to extension).
Wrench fault Synonym for a strike-slip fault. It was commonly used in the petroleum geology literature, typically in reference to a regional-scale continental strike-slip fault.
Aydin, A., and Nur, A., 1982. Evolution of pull-apart basins and their scale independence. Tectonics, 1, 91–105.
Biddle, K. T., and Christie-Blick, N., 1985. Strike-slip deformation, basin formation, and sedimentation: Society of Economic Paleontologists and Mineralogists Special Publication 37, SEPM, Tulsa, 386 p.
Burchfiel, B. C., and Davis, G. A., 1973. Garlock fault: an intracontinental transform fault. Geological Society of America Bulletin, 84, 1407–1422. Freund, R., 1974. Kinematics of transform and transcurrent faults. Tectonophysics, 21, 93–134.
Garfunkel, Z., 1986. Review of oceanic transform activity and development. Geological Society of London Journal, 143, 775–784.
Naylor, M. A., Mandl, G., and Kaars-Sijpestein, C. H., 1986. Fault geometries in basement-induced wrench faulting under different initial stress states. Journal of Structural Geology, 7, 737–752.
Nelson, M. R., and Jones, C. H., 1987. Paleomagnetism and crustal rotations along a shear zone, Las Vegas Range, southern Nevada. Tectonics, 6, 13–33.
Sengör, A. M. C., 1979. The North Anatolian transform fault: its age, offset, and tectonic significance. Geological Society of London Journal 136, 269–282.
Sylvester, A. G., 1988. Strike-slip faults. Geological Society of America Bulletin, 100, 1666–1703.
Tchalenko, J. S., 1970. Similarities between shear zones of different magnitudes. Geological Society of America Bulletin, 81, 1625–1640.
Wilcox, R. E., Harding, T. P., and Seely, D. R., 1973. Basic wrench tectonics. American Association of Petroleum Geologists Bulletin, 57, 74–96.
Woodcock, N. H., and Schubert, C., 1994. Continental strike-slip tectonics. In Hancock, P. L., ed., Continental Deformation. Pergamon Press: Oxford, pp. 251–263.