Modeling suggests that oblique extension facilitates rifting and continental break-up

• Published in: Journal of Geophysical Research: Solid Earth Vol. 117; no. B8
• Main Authors: Brune, Sascha, Popov, Anton A., Sobolev, Stephan V.
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 01.08.2012; American Geophysical Union
• Subjects: continental break-up; Earth sciences; Earth, ocean, space; Exact sciences and technology; Geophysics; mathematical modeling; numerical modeling; oblique rifting; Plate tectonics; Rifting; tectonic forces; Middle East; Gulf of California; Asia; Atlantic Ocean; Africa; Equatorial Atlantic; Pacific Ocean; Northeast Pacific; East Africa; Ethiopia; North Pacific; Dead Sea; strain; Dimensionality; extension; Mechanical model; separation; rift zones; rifting; tectonics; faults; Modeling; direction; Gondwana
• ISSN: 0148-0227; 2169-9313; 2156-2202; 2169-9356
• DOI: 10.1029/2011JB008860

In many cases the initial stage of continental break‐up was and is associated with oblique rifting. That includes break‐up in the Southern and Equatorial Atlantic, separation from eastern and western Gondwana as well as many recent rift systems, like Gulf of California, Ethiopia Rift and Dead Sea fault. Using a simple analytic mechanical model and advanced numerical, thermomechanical modeling techniques we investigate the influence of oblique extension on the required tectonic force in a three‐dimensional setting. While magmatic processes have been already suggested to affect rift evolution, we show that additional mechanisms emerge due to the three‐dimensionality of an extensional system. Focusing on non‐magmatic rift settings, we find that oblique extension significantly facilitates the rift process. This is due to the fact that oblique deformation requires less force in order to reach the plastic yield limit than rift‐perpendicular extension. The model shows that in the case of two competing non‐magmatic rifts, with one perpendicular and one oblique to the direction of extension but otherwise having identical properties, the oblique rift zone is mechanically preferred and thus attracts more strain. Key Points Oblique extension facilitates the rift process in non‐magmatic settings Shearing a continent requires up to two times less force than rifting it An oblique rift zone attracts more strain than a competitive normal rift