Figure captions to figures stored in Electronic archive - Continental break-up mechanism; lessons from intermediate- and fast-extension settings 

Electronic archive Fig. 1. (a) Stretching-dominated extension model characterizing slow-spreading ridge (Escartín et al., 2003). (b) Buoyancy-dominated extension model characterizing fast-spreading ridge (Dick et al., 2000).

Electronic archive Fig. 2. Tectonic map of East India (Ray, 1963) with reflection seismic grid located atop isostatic residual anomaly map (Fugro Robertson Inc., 2006; GX Technology, 2007). The tick blue line indicates the boundary between the Proterozoic mobile belts in the southeast juxtaposed to the Achaean cratons in the northwest. The correlation of interpreted reflection seismic sections and isostatic residual anomaly data indicates that basins are imaged as negative anomalies (see Nemčok et al., 2011a). It further indicates that large structural highs along the shelf edge are imaged by positive anomalies, as well as the proto-oceanic corridor (shown in Nemčok et al., 2011a) in front of the continental margin.

Electronic archive Fig. 3. Match of the observed (bold) and calculated (thin) gravity and magnetic curves along the interpreted dip-oriented reflection seismic section GXT 1000 (GX Technology, 2007) through the East Indian continental margin. Sedimentary cover interpreted with the help of well data contains four layers, s1, s2, s3 and s4, with downward increasing density. Continental crust is divided into upper, middle and lower crustal layers; ucc, mcc and lcc. The same division, uoc, moc and loc, is applied to the oceanic crust. poc denotes proto-oceanic crust. Note that the density of the proto-oceanic crust located between continental and oceanic crusts and required to achieve the match is denser than density of the oceanic crust. Density variations inside poc volume can be attributed to various degrees of serpentinization (see Wilson et al., 2003). Densities are listed in gcm-3.

Electronic archive Fig. 4. Reflection seismic section through the internal portion of the Gabon continental margin showing the elevated Moho underneath the thinned continental crust (data from GX Technology, 2005b; interpretation from Nemčok & Rosendahl, 2006). Listric normal faults sole out at the Moho level.

Electronic archive Fig. 5. Reconstructed break-up trajectory along the future Equatorial Atlantic and adjacent ends of Central Atlantic and South Atlantic (modified from Nemčok et al., 2011b). Gray – reconstruction underlap, yellow – reconstruction overlap, blue/white dashed line – oceanic/continental boundary interpreted from African data, black/white dashed line – oceanic/continental boundary interpreted from South American data. Arrows indicate strike-slip-controlled break-up segments in the future Equatorial Atlantic region. The most prominent are the St Paul (SP) and Romanche (R) transform margins. All four strike-slip fault systems indicated by arrows were divided during rifting by three regions with a roughly orthogonal extension, forming a system of distributed accommodation zones.

Note the large amount of planar anisotropies occurring in the upper crust of both continents. An especially dense system of shear zones and faults can be observed in the northeastern corner of South America. See Figure 4 and text for explanations in all four examples.

Electronic archive Fig. 6. (a) Dip-oriented section through the East Indian margin imaging its proximal portion. pr2 – top of the post-rift strata 2, pr1 – top of the post-rift strata 1, r – top of the syn-rift strata, b – top of the crystalline basement. Note a system of steeply-dipping listric normal faults controlling large sediment catchment areas. (b) Dip-oriented section through the East Indian margin imaging its distal portion. pr – top of the post-rift marker horizon, r – top of the syn-rift strata, b – top of the crystalline basement, lcc – top of the lower continental crust, Moho – top of the continental lithospheric mantle. Note a system of shallowly-dipping listric normal faults controlling small sediment catchment areas. Most of their fill is dominated by volcanic rocks.

Electronic archive Fig. 7. Comparison of deformational behavior of continental upper crust, lower crust and lithospheric mantle, and associated principal stresses under the same regional extension but different thermal regimes (Henk, 2005, 2006). The low and high strength scenarios have surface heat flow values of 85 and 45 mWm-2, respectively. The lithologic section is the same for both. See text for further explanations.