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Pull-apart basin
In geology, a basin is a region where subsidence generates accommodation space for the deposition of sediments. A pull-apart basin is a structural basin where two overlapping (en echelon) faults or a fault bend creates an area of crustal extension undergoing tension, which causes the basin to sink down. Frequently, the basins are rhombic or sigmoidal in shape. Dimensionally, basins are limited to the distance between the faults and the length of overlap.〔Frisch, Wolfgang, Martin Meschede, and Ronald C. Blakey. ''Plate tectonics: Continental drift and mountain building''. Springer, 2010.〕 Pull-apart basins are also referred to as overlapping-tension-zones (OTZ).〔Kearey, Philip, Keith A. Klepeis, and Frederick J. Vine. Global tectonics. John Wiley & Sons, 2009.〕
==Mechanics and fault configuration==
The inhomogeneity and structural complexity of continental crust causes faults to deviate from a straight course and frequently causes bends or step-overs in fault paths. Bends and step-overs of adjacent faults become favorable locations for extensional and compressional stress or transtension and transpression stress, if the shear motion is oblique. Pull-apart basins form in extensional to transtensional environments along fault bends or between two adjacent left-lateral faults or two right-lateral faults. The step-over or bend in the fault must be the same direction as sense of motion on the fault otherwise the area will be subject to transpression.〔
For example, two overlapping left lateral fault must have a left-step-over to create a pull-apart basin. This is illustrated in the accompanying figures.
A regional strike slip fault is referred to as a principle displacement zone (PDZ). Connecting the tips of step over faults to the opposite fault are bounding basin sidewall faults. Recent sandbox models have shown that the geometry and evolution of pull-apart basins varies greatly in pure-strike slip situations versus transtensional settings. Transtensional settings are believed to generate greater surface subsidence than pure-strike slip alone.〔Wu, Jonathan E., Ken McClay, Paul Whitehouse, and Tim Dooley. "4D analogue modelling of transtensional pull-apart basins." Marine and Petroleum Geology 26, no. 8 (2009): 1608–1623.〕
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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