Tectono-stratigraphic signature of multiphased rifting on divergent margins (deep-offshore southwest Iberia, North Atlantic)

[1] Regional 2D multichannel seismic, borehole, dredge and outcrop data, together with burial models for strata in southwest Iberia, are used to investigate the tectono-stratigraphic signature of multiphased rifting on divergent margins. Our burial model reveals that Mesozoic extension occurred during three main phases, each comprising distinct subsidence pulses separated by short-lived periods of crustal uplift. The importance of the three phases varies across discrete sectors of the margin, each one revealing similar depositional architectures and associated tectonic systems tracts: 1) the Rift Initiation phase, characterized by incipient subsidence and overall aggradation/progradation over a basal unconformity, 2) the Rift Climax phase, which marks maxima of tectonic subsidence and is characterized by retrogradation-progradation, and 3) the Late Rift phase, recording the progradational infill of the basin and the effects of eustasy. The Rift Initiation systems tracts comprise Sinemurian and late Callovian-early Oxfordian strata. Marine units in the Pliensbachian and Late Oxfordian-Kimmeridgian represent the Rift Climax phase, a period marked by the development of Maximum Flooding Surfaces. Late Rift deposits were identified in the Rhaetian-Hettangian, Toarcian-Bathonian and Kimmeridgian-Berriasian. The results of this work are important to the economic exploration of deep-offshore rift basins, as they reveal that sequence stratigraphy can be used to predict sedimentary facies distribution in more distal segments of such basins. Significantly, this work recognizes that multiple tectonic-stratigraphic (rift) cycles can occur on deep-offshore rift basins, from the onset of rift-related extension until continental break-up, a character that contrast to what is known from deep-sea drilling data from the distal margin of Northwest Iberia.