Basins in which subsidence accompanied strike-slip deformation are known from the Proterozoic to Holocene. They occur in virtually all plate-tectonic settings (transform, convergent, and divergent plate margins, and plate interiors), and they are underlain in different places by crustal types ranging from continental to oceanic. In transform (wrench) systems, basins develop where fault strands splay, bend, or overstep in a divergent sense, and where plate motion is obliquely divergent to the strike of individual faults. Basins also develop between fault blocks rotating about vertical axes, and at some convergent splays, bends, and oversteps as a result of crustal loading. Basins formed by overall crustal extension (e.g., grabens) and by crustal loading (e.g., foredeeps) m y terminate against strike-slip faults.

Basins associated with strike-slip deformation are filled with a wide range of sedimentary facies, deposited in nonmarine to deep marine environments. The principal controls on sedimentation are crustal type and thickness, plate-tectonic setting, amounts and rates of subsidence, relative sea level, topographic relief, and climate. Abrupt facies changes and discontinuities are relatively common. Subsidence rates are generally high, but there is significant variation within individual basins and from one basin to another. The type and degree of associated volcanic activity at any locality are related to tectonic setting and the amount of lithospheric extension. Heat-flow history is extremely variable, even within a single basin; consequently, the level of maturation of petroleum source ocks is notoriously difficult to predict in these types of basins.

End_of_Article - Last_Page 462------------