Abstract
During extension of the continental lithosphere, rift basins develop. These are often initially offset, and must interact and connect in order to create a continuous rift system that may ultimately achieve break-up. When simulating extensional tectonics and rift interaction structures, analogue and numerical modellers often apply a continuous extension rate along the strike of a rift or rift system. Yet in nature significant extension velocity variations occur along rifts and plate boundaries as a natural consequence of tectonic plates moving apart about a pole of rotation, resulting in rotational extension, and associated rift propagation and structural gradients. Here we present various analogue tectonic experiments to assess rift interaction structures forming in orthogonal extension settings versus rotational extension settings. Our modelling efforts show that rotational extension and orthogonal extension produce significantly different large-scale structures. Rotational extension can cause important variations in rift maturity between rift segments, delay rift interaction zone development, and make rift segments propagate in opposite directions. Still, local features in a rotational extension system can often be regarded as evolving in an orthogonal extension setting. Furthermore, we find that various degrees of rift underlap produce three basic modes of rift linkage structures. Low underlap distance (high angle φ) experiments develop rift pass structures. With increasing underlap distance (φ = ca. 40°), transfer zone basins develop. High degrees of underlap (φ ≤ 30°) tend to result in en echelon sub-basins. Our results match with data from previous modelling efforts and natural examples. We furthermore propose a large-scale tectonic scenario for the East African Rift System based on rotational extension and associated rift propagation. These insights may also be applicable when studying other large-scale rift systems.
Highlights
An important feature associated with rift structures is their tendency to develop along structural inheritances such as old faults or shear zones, locally thinned lithosphere or old orogenic belts (e.g. Morley et al, 1990; Nelson et al, 1992; Dyksterhuis et al, 2007; Corti, 2012 and reference therein)
We present a selection of the final model results in an overview figure (Fig. 3), which depicts the various structures that develop under orthogonal extension and rotational extension conditions (Fig. 3a and b, respectively)
Orthogonal extension models and rotational extension models show large-scale differences in along-strike rift development (Mondy et al, 2018; Zwaan et al, 2020, Figs. 3–5), we find that both model set-ups develop a very similar sequence of rift linkage structures, which are in this study strongly depending on the degree of underlap
Summary
An important feature associated with rift structures is their tendency to develop along structural inheritances such as old faults or shear zones, locally thinned lithosphere or old orogenic belts (e.g. Morley et al, 1990; Nelson et al, 1992; Dyksterhuis et al, 2007; Corti, 2012 and reference therein). Chorowicz, 2005; Corti, 2012, Fig. 1b) and the North Sea Rift System Rift linkage zones are important structures during rifting and continental break-up, as they may represent the predecessors of subsequent transform faults in the oceanic domain (e.g. the Labrador Sea, the South Atlantic or the Knipovich ridge in the Arctic, Fig. 1c, Bellahsen et al, 2003, Heine et al, 2013; Heron et al, 2019). Linkage zones can influence the migration of melts and hydrocarbons, providing complex structural traps such as present in the Viking Graben in the North Sea and in rift and passive margin settings in general When simulating lithospheric extension, modellers routinely apply a constant extension rate along the strike of a rift or rift system
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
