Captions to online figures

A4 paper size versions of seismic sections presented in Figures 6  and 7 of Quirk et al. 2012.

Figs. 1a & 1b.  Western and eastern parts of Fig. 6a in Quirk et al. 2012.  2D pre-stack depth migrated seismic section through the Campos basin (see Fig. 3 in Quirk et al. 2012 for approximate location).  The ocean is to the right (ESE).  Fig. 4 = approximate location of the generic stratigraphic column in Figure 4 in Quirk et al. 2012.  Pink horizon (113 Ma, top Aptian) = top salt.  Purple horizon (117 Ma) = base salt.  Green and yellow horizons = intra-sag (early Aptian).  Black horizon (123 Ma, base Aptian) = end of rift unconformity.  Orange horizon (130 Ma, base Barremian) = approximate base of syn-rift siliciclastics and top of Hauterivian basalts.  Bright red lines = landward-dipping low-angle detachment faults (early Barremian syn-rift) with representative angle of dip indicated.  Grey lines = seaward-dipping normal faults (late Barremian syn-rift).  White lines = post-sag normal faults at outer edge of continental margin (Albian-Turonian age).  Dark red shading-white dashed lines = top of basement domes interpreted as core complexes.   Burgundy red = interpreted base of upper crust and approximate top of magmatic underplate, representing the brittle-ductile transition during Barremian rifting.  Yellow line = continent-ocean boundary (COB).  OVH = outer volcanic high (early Aptian).  Numerous basaltic dykes are inferred to occupy the syn-rift section closest to COB, as indicated, limiting the amount of compaction-related subsidence in the overlying sag.  Orange curved arrow indicates fault separation and rotation due to stretching.  The section is vertically exaggerated (the real angle of dip of one landward-dipping fault is indicated – 20o).  Seismic image is courtesy of TGS and WesternGeco.

Figs. 2a & 2b.  Western and eastern parts of Fig. 6b in Quirk et al. 2012.  Same sections as Figures 1a and 1b (above) flattened on base salt to illustrate the relative low relief of the end of rift unconformity (black horizon).  Onlap geometries are highlighted with black half arrows, indicating that exposed escarpments and ridges were less than 500 m in height.  These were completely buried by the time the yellow horizon was deposited in the lower part of the sag.  Only draping geometries are observed in upper part of the sag above the green horizon.  Seismic image is courtesy of TGS and WesternGeco.

Figs. 3a & 3b.  Western and eastern parts of Fig. 7 in Quirk et al. 2012.  WNW-ESE regional 2D pre-stack depth migrated seismic section through northernmost part of Benguela Basin (see Fig. 3 in Quirk et al. 2012 for approximate location).  The ocean is to the left (WNW).  Horizons are: dark pink = top of Aptian salt; salmon pink = base of allochthonous salt; orange = top of Aptian volcanics; purple = top of sag/base of autochthonous salt (117 Ma); black = base of sag/end of rift unconformity (123 Ma, base Aptian); dashed blue = top of oceanic crust (<123 Ma).  Bright red lines = seaward-dipping syn-rift normal faults.  Grey lines = landward-dipping syn-rift normal faults.  Dashed white-dark red lines = top of basement domes interpreted to represent extensional core complexes.  Yellow line = Albian-Turonian normal fault in oceanic crust, probably related to departure of mantle plume.  Representative beta factors (β) are also shown based on assumed initial continental crustal thickness of 30 km and ignoring the thickening effect of underplating.  Seismic image is courtesy of WesternGeco and Sonangol.