Dylan Alexander Vasey , John Naliboff, Eric S. Cowgill, Sascha Brune, Anne C Glerum , Frank Zwaan

Although many collisional orogens result from subduction of oceanic lithosphere between two continents, some orogens form by strain localization within a continent via inversion of extensional structures inherited during continental rifting. Intracontinental rift-inversion orogens exhibit a wide range of first-order structural styles, but the underlying causes of such variability have not been extensively explored. Here, we use ASPECT to numerically model intracontinental rift inversion and investigate the impact on orogen structure of rift velocity/thermal structure, rift duration, post-rift cooling, and convergence velocity. Our models reproduce the natural variability of rift-inversion orogens, which can be categorized using three endmembers: asymmetric underthrusting (Style AU), distributed thickening (Style DT), and localized polarity flip (Style PF). Inversion of slow/cold rifts tends to produce orogens with more localized deformation (Styles AU and PF) than those resulting from host/fast rifts. However, multiple combinations of the parameters investigated here can produce the same structural style. Thus, there is not a unique relationship between orogenic structure and the conditions during and prior to inversion. Because the structure of rift-inversion orogens is highly contingent upon the initial conditions prior to inversion, knowing the geologic history that preceded rift inversion is essential for translating orogenic structure into the processes that produced that structure.