T54C-02
3D Numerical Experiments of Lithospheric Transtension Reveal Complex Crustal-Scale Flow and Strain Partitioning in Transdomes
Friday, 18 December 2015: 16:15
306 (Moscone South)
Patrice F Rey1, Luke Stephen Mondy1, Guillaume Duclaux2, Christian P Teyssier3 and Donna L Whitney4, (1)University of Sydney, Sydney, Australia, (2)University of Bergen, Department of Earth Science, Bergen, Norway, (3)Univ of Minnesota, Minneapolis, MN, United States, (4)University of Minnesota Twin Cities, Minneapolis, MN, United States
Abstract:
We have used Underworld to perform a series of numerical experiments involving a 256 x 256 x 128 km domain, at a grid resolution of 1.33 km. The kinematic boundary conditions simulate a lithospheric-scale pull-apart setting. We compare the structural and thermal evolution of a model involving a crust of thickness 40 km (TMoho=540ºC) with a model with a crust of thickness 60 km (TMoho=830ºC). We show that in the thick, hot crust model the flow in the pull-apart region is strongly partitioned between the strong upper crust and the weak lower crust. The weak, deep crust flows toward the pull-apart region to isostatically compensate the stretching and thinning of the upper crust. In contrast, the velocity field in the upper crust remains parallel to the imposed direction of extension. In the pull-apart region a transdome, made of two parallel foliation folds (or sub-domes), forms. In the dome, fabrics evolve from strong vertical flattening in between the two sub-domes, to shallow dipping constriction roughly parallel to the direction of extension in the upper part of the transdome.
