Diachronous evolution of Late Jurassic–Cretaceous continental rifting in the northeast Atlantic (west Iberian margin)

Abstract

Regional (2‐D) seismic reflection profiles, outcrop, and borehole data are used to characterize the evolution of deep offshore sedimentary basins in southwest Iberia (Alentejo Basin). The interpreted data indicate the bulk of Late Jurassic–earliest Cretaceous subsidence occurred in the present‐day continental slope area, as shown by (1) significant thickening of synrift strata basinward from a slope‐bounding fault system (SFS), west of which the total thickness of sediment can reach more than 9.0 km, and (2) relatively thin Mesozoic strata east of the SFS, where thickening of synrift units against principal faults is limited. Five principal regressive events and their basal unconformities reflect tectonic uplift and relative emersion in proximal basins, which were located on the rift shoulder to subsiding tilt blocks west of the SFS. These regressive events are correlated with major rift‐related events occurring on the deeper margin. Direct comparisons with the Peniche Basin of northwest Iberia reveal that significant portions of the Iberian lower plate margin were uplifted and eroded during the last stages of continental rifting. This process was repeated at different times (and in different areas) as the locus of rifting and continental breakup migrated northward. As a result, two distinct rift axes are recognized in west Iberia, a first axis extending from the Porto Basin to the Alentejo Basin and a second axis located on the outer proximal margin north of 38°30N. In addition, the SFS delimited (1) prograding deposits of Cretaceous‐Paleogene age and (2) late Cenozoic deposits draping the modern continental slope. These latter facts demonstrate that on lower plate passive margins, the relative position of the continental slope is established during the final rifting episode(s) preceding continental breakup.

Tectonic variation and structural evolution of the West Greenland continental margin

“…(Gregersen et al, 2013). However, the identification of the transition between syn-rift and post-rift settings may not always be reflected by a simple breakup unconformity (Alves et al, 2009;Soares et al, 2012). These authors show that the "breakup unconformity" is a Lithospheric…”

Origin and consequences of western Mediterranean subduction, rollback, and slab segmentation

“…Pre‐Eocene extension in the SW Mediterranean region may have occurred at multiple stages after the Variscan orogeny, but the most likely timing for exhumation of subcontinental mantle from below the Iberian (Balearic) margin is during the Jurassic breakup of Pangea and the opening of the Piemonte‐Ligurian Ocean. Aside from evidence for Jurassic mantle exhumation in the Rif, exhumed subcontinental mantle is still present offshore western Iberia [e.g., Alves et al ., ] and has been reconstructed in the Pyrenees [ Lagabrielle and Bodinier , ] and in the Alps [ Mohn et al ., ]. We thus agree with suggestions of Michard et al .…”

Thermal Evolution of Asymmetric Hyperextended Magma‐Poor Rift Systems: Results From Numerical Modeling and Pyrenean Field Observations

“…Despite these recent studies, the thermal evolution and architecture of rifted margins and especially the consequence of asymmetric rifting remain poorly understood. Notably, the spatial and temporal evolution of rift systems is shown to be complex (Alves et al, ; Mohn et al, ; Naliboff et al, ; Savva et al, ; Tugend, Manatschal, Kusznir, & Masini, ) and its control on the rift‐related thermal evolution remains at present unconstrained. Simple correlations between isolated, punctual observations within a rift system and the overall thermal architecture and evolution of the entire basin are not straightforward.…”