| Continents extend in a variety of ways including narrow rifts, wide rifts, and core complexes. During normal faulting associated with rifting, rocks are exhumed from depth via the tectonic unroofing resultant from the fault offset itself and by erosion of the faulted topography. In this thesis, I explore four regional, plate tectonic-scale scenarios of rifting and exhumation to further our understanding of the geodynamical processes responsible for determining the style in which continents rift and exhume rocks from depths of a few kilometers to up to 100-200 km, focusing on the effects of plateau collapse, sedimentation, diking, and subduction of small slivers of continental material. The effects of thermal structure and plateau collapse on extensional systems are investigated to understand when a plateau edge may remain after rifting. Continental plateau collapse is used to explain the development of the West Antarctic Rift System, a broad region of thin, hot crust, and the adjacent Transantarctic Mountains. The plateau collapse model is expanded to include the effects of sedimentation derived from the far-field and test its influence on distributed rifting. Sedimentation is able to quicken the transition from wide to narrow rifting and such a scenario is proposed to explain features in the Northern Gulf of California. In contrast to the collapse of thin lithosphere in a plateau, cold, normally thick lithosphere may not extend unless the system is first magmatically weakened. As little as ∼4 km of maximum dike opening can sufficiently weaken normal lithosphere to the point of tectonic rifting. Lastly, while wide rifting and core complex rifting can exhume rock from mid to lower crustal levels, a third subduction related mechanism for exhumation may be required to explain the presence of ultrahigh pressure rocks in orogenic systems. The subduction and exhumation of slivers of continental material is related to the buoyancy of the subducted block and the strength of its coupling to the down-going slab. The behavior of the slab, namely its velocity, slab dip, and rate of rollback, can influence the depth from which the continental sliver is exhumed. |
