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Volume 9, issue 5 | Copyright
Solid Earth, 9, 1187-1206, 2018
https://doi.org/10.5194/se-9-1187-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 26 Oct 2018

Research article | 26 Oct 2018

Oblique rifting: the rule, not the exception

Sascha Brune1,2, Simon E. Williams3, and R. Dietmar Müller3,4 Sascha Brune et al.
  • 1GFZ German Research Centre for Geosciences, 14473 Potsdam, Germany
  • 2Institute of Earth and Environmental Science, University of Potsdam, 14476 Potsdam-Golm, Germany
  • 3EarthByte Group, School of Geosciences, University of Sydney, Sydney, New South Wales 2006, Australia
  • 4Sydney Informatics Hub, University of Sydney, Sydney, New South Wales, Australia

Abstract. Movements of tectonic plates often induce oblique deformation at divergent plate boundaries. This is in striking contrast with traditional conceptual models of rifting and rifted margin formation, which often assume 2-D deformation where the rift velocity is oriented perpendicular to the plate boundary. Here we quantify the validity of this assumption by analysing the kinematics of major continent-scale rift systems in a global plate tectonic reconstruction from the onset of Pangea breakup until the present day. We evaluate rift obliquity by joint examination of relative extension velocity and local rift trend using the script-based plate reconstruction software pyGPlates. Our results show that the global mean rift obliquity since 230Ma amounts to 34° with a standard deviation of 24°, using the convention that the angle of obliquity is spanned by extension direction and rift trend normal. We find that more than  ∼ 70% of all rift segments exceeded an obliquity of 20° demonstrating that oblique rifting should be considered the rule, not the exception. In many cases, rift obliquity and extension velocity increase during rift evolution (e.g. Australia-Antarctica, Gulf of California, South Atlantic, India-Antarctica), which suggests an underlying geodynamic correlation via obliquity-dependent rift strength. Oblique rifting produces 3-D stress and strain fields that cannot be accounted for in simplified 2-D plane strain analysis. We therefore highlight the importance of 3-D approaches in modelling, surveying, and interpretation of most rift segments on Earth where oblique rifting is the dominant mode of deformation.

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Fragmentation of continents often involves obliquely rifting segments that feature a complex three-dimensional structural evolution. Here we show that more than ~ 70 % of Earth’s rifted margins exceeded an obliquity of 20° demonstrating that oblique rifting should be considered the rule, not the exception. This highlights the importance of three-dimensional approaches in modelling, surveying, and interpretation of those rift segments where oblique rifting is the dominant mode of deformation.
Fragmentation of continents often involves obliquely rifting segments that feature a complex...
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