ABSTRACT On magma poor rifted margins, the boundary between deformed and overlying post tectonic stratigraphy is a significant and long recognised feature: however its interpretation and origin remain debated. The boundary, the Top Taper Interface (TTI), forms the upper surface of tapered continental crust and pre/syn tectonic stratigraphy typical of rifted margins. Extending interpretations of the TTI across rifted margins into deep water where data are scarce is often challenging. The Iberian Atlantic Margin offers rare deep water (> 4 km) calibration but lacks borehole data across a key area, the ‘necking domain’, which lies between deep water and the proximal margin. By contrast the necking domain is well calibrated elsewhere around the European North Atlantic rim. Fault offsets often exceeding 1 km, with minimal syn‐tectonic hanging wall growth, are a recurring feature of the TTI. Re‐examining the Iberian margin and its North Atlantic counterparts indicates the TTI develops in < 10 Ma with fault generated subsidence and sediment starvation, immediately preceding a Jurassic—earliest Cretaceous termination, pause or migration of active extension in the continental crust. Significant basin reconfiguration is indicated by the often complex sub‐crop of the TTI. North Atlantic data indicate the TTI is often associated with stratigraphic condensation driven by deepening. Globally such interfaces occur regardless of sediment budget indicating an increase in basin width and volume that outpaces sediment delivery. The widening of the basin relative to earlier upper crustal graben results from faulting localised across a long‐wavelength crustal neck thinned during active extension, preceding a cessation or migration of active extension. However, observations from the European North Atlantic rim basins indicate that this process should also account for failed necking domains that did not reach such advanced stages of extension.
Erratt et al. (Tue,) studied this question.