Plate Tectonics

Chapter 6 covers continental rifting and rift-related processes that operate when continental lithosphere is thinned and broken. It covers the two fundamental modes of rift initiation; active and passive rifting. It also cover the role of mantle plumes and pre-rift structures that weaken the lithosphere. Magmatism typically varies along rift systems and is often related to plume influence during rift initiation. The main structural elements of rifts are presented, from rift transfer zones to fault relay ramps, together with the evolution of rifts in terms of fault growth, strain, crustal thinning and rift (a)symmetry. While some rifts open orthogonally, most rifts experience oblique rifting. Other rifts again show evidence of two or more phases of extension, and the interference between the two phases in terms of fault orientation and interaction is discussed. Different tectonic settings, such as back-arc rifting, transform fault settings, and orogen-related rifting are covered. The deposition of sediments in relation to structural elements is important, and both synrift and postrift sedimentation are discussed. Rifts also host important hydrocarbon and mineral resources, and examples from northern Europe and North America are provided in this chapter.