- © The Mineralogical Society Of America
Extension and associated tectonic exhumation have been described across a diverse spectrum of geodynamic environments, ranging from lithospheric-scale extension along divergent plate margins to extensional faulting within compressional orogenic belts. Normal faulting structurally dominates extensional tectonic environments such as passive continental margins, intra-continental extensional provinces and rifts, extensional back-arc basins, and mid-oceanic ridge inside corner extensional systems. In addition, structural domains characterized by normal faulting or extensional crustal attenuation commonly occur within collisional orogens and within transcurrent deformation belts. Numerous studies over the past decades have investigated extensional faulting in these different extensional tectonic environments to elucidate the architecture of extensional fault systems, the driving forces associated with crustal or lithospheric extension, and the timing and rates of extensional tectonic processes.
Many important aspects of extensional tectonics remain controversial, such as (1) the forces driving initiation of extension and rifting and their variation through time (e.g., Jones et al. 1996; Atwater and Stock 1998), (2) the parameters controlling the temporal and spatial distribution of extensional strain in the lithosphere (e.g., Buck 1991; Kusznir and Park 2002), (3) the factors influencing the geometry, kinematics, and mechanics of extensional fault systems (e.g., Wernicke and Burchfiel 1982; Jackson and White 1989; Buck 1991), (4) the role of magmatism during extensional faulting (e.g., Sengor and Burke 1978; Gans et al. 1989; Armstrong and Ward 1991; Axen et al. 1993), and (5) the interplay between extensional tectonism, erosion, and sedimentation in evolving extensional provinces (e.g., Ehlers et al. 2001, 2003).
One of the primary hurdles in resolving many of these questions has been the lack of constraints on the timing and rates of geological processes accommodating extension. Traditionally, the most direct way to assess the timing of normal faulting has been to date stratigraphic or intrusive/extrusive …