Abstract The thermal evolution of continental rifted margins is key to understanding margin subsidence and hydrocarbon prospectivity. Observed heat-flow values, however, do not always comply with classic rifting models. Here, we use 2D numerical models to investigate the relationship between rifting, sedimentation and thermal history of margins. We find that during the synrift, the basement heat-flow and temperature are not only controlled by extension factor, but also by synrift sediment thickness and the evolution of deformation. As this progressively focuses oceanward, the proximal sectors thermally relax, while the distal sectors experience peak temperatures. In the post-rift, the lithosphere under the hyperextended margins does not return to its original state, at least for c. 100 Myr after break-up. Instead, it mimics that of the adjacent oceanic plate, which is thinner than the original continental plate. This results in heat-flow increasing oceanward at post-rift stages, when classic rifting theory predicts complete thermal relaxation. Our models also predict slightly increased heat-flows in the adjacent oceanic crust, potentially extending hydrocarbon plays into distal margins and oceanic crust, previously discarded as immature. Finally, our models indicate that commonly used temperature approximations to calculate heat-flow during rifting may strongly differ from those occurring in nature.

Abstract New geochronological (U–Pb isotope dilution thermal ionization mass spectrometry), geochemical and isotopic data from Upper Ordovician felsic volcanic rocks recorded in the Pyrenees and Mouthoumet massifs, SW Europe, suggest that this volcanic activity is more widely represented than previously accepted, and allows a better refinement of the age span involved in the Sardic Unconformity. This Sandbian volcanism represents the final pulse of the Sardic tectonothermal event, starting with the Floian–Darriwilian emplacement of voluminous plutonic rocks and the contemporaneous erosion of the uplifted pre–Upper Ordovician basement, and followed by a tholeiitic volcanism contemporaneous with extensional features and the opening of (half-)grabens finally sealed by Hirnantian glaciomarine deposits. The Sardic-related lithospheric extension may be linked to thermal doming originated by a superplume activity that caused, in turn, an extensive crustal melting responsible for the onset of the felsic (calc-alkaline-dominated), Floian–Darriwilian intrusive and Sandbian extrusive magmatism along the northern margin of Gondwana.

Abstract The Cambrian Atlas – Ossa–Morena – North Armorican Rift extended along West Gondwana from the end of the Pan-African and Cadomian orogenies until the diachronous beginning of drift conditions related to the opening of the Rheic Ocean. The along-axis rift cross-cut the western parts of the Anti-Atlas, High Atlas and Coastal Meseta, which were linked to the Ossa–Morena Zone and the North Armorican Domain, whereas several joint tectonic branches connected with off-axis rift transects of the Central Iberian, West Asturian–Leonese and Cantabrian zones (Iberian Massif), the Central and South Armorican domains, the Occitan Domain, the Pyrenees, and southern Sardinia. The pre-rift unconformity, post-dating the orogenic collapse, is characterized by initial (half-)graben development and subsequent infill, with slope-related breccias and conglomerates controlled by the denudation of surrounding uplands. Synrift pulses show regional extension and are distinctly identifiable on the top of rift shoulders, recording episodes of carbonate production due to their association with karst and hydrothermal processes. The break-up unconformity ranges from volcanic-free angular discordances and paraconformities to generalized uplift and denudation of subaerially exposed areas, associated with the onset of granite-dominant large igneous provinces (LIPs). The Furongian–Tremadocian (Toledanian) and Ordovician (Sardic) phases have been interpreted as due to: (i) Andean-type subduction magmatism reaching the crust in an arc–back-arc setting; (ii) post-collisional decompression melting without significant mantle involvement; and (iii) partial melting of the lower continental crust affected by the underplating of hot mafic magmas linked to superplumes.

Abstract Well Mondot-1 was drilled, cored and logged behind an outcrop of the Eocene Sobrarbe deltaic complex in the Aínsa Basin, Spanish Pyrenees. The data acquired represent a fluvial-dominated delta system prograding over a carbonate slope in the presence of active tectonism, and form part of a basin-to-grain teaching set for subsurface professionals. This paper highlights the workflow step(s) to move from a 1D core description to 2D and 3D correlations, including some of the pitfalls caused by rapid lateral facies variability, which is a common challenge in subsurface reservoir description. The core allows direct log-to-lithology comparison across a full deltaic succession. In the proximal and distal delta fronts, there are clear differences from the closely adjacent outcrop that are ascribed to lateral facies changes and delta front slumping. Two approaches to core display are described, as means towards making such data available to a wider audience: an augmented reality display run over a slabbed core, and a virtual whiteboard display carrying easily scalable viewing possibilities. These approaches can be deployed for other cores, allowing visualization and analysis where people are otherwise unable to travel to the physical location, or in circumstances where the core is now inaccessible.

Abstract For the west European regional chronostratigraphic framework, the Cantabrian substage was conceived as covering a widely apparent stratigraphic gap between the top of the Westphalian and the base of Stephanian A, the lowest unit of the Stephanian. A continuous depositional history covers this time gap in the Cantabrian region of Spain; the upper limit of this interval was defined by the succeeding Barruelian substage, equivalent to Stephanian A. Intense tectonic and magmatic activity characterizes this period; the Iberian orogenic belt was an essentially linear feature buckled through the Late Pennsylvanian into the tightly folded Cantabrian Orocline. This evidences an extensive southern foreland to the Variscides, in which the coal-swamp biome persisted through the Late Pennsylvanian, supporting biostratigraphical correlation with the Donbass. New high precision U–Pb CA-ID-TIMS radiometric dating of tonstein horizons supports a preliminary time-framework of regional substages: base of the Asturian (proposed, ex-Westphalian D) c. 310.7 Ma; base of the Cantabrian c. 307.5 Ma; base of the Barruelian (ex-Stephanian A) c. 304.9 Ma; base of the Saberian (proposed) c. 303.5 Ma. The Cantabrian and Barruelian embrace the entire Kasimovian of the global time-scale, and the top of the Barruelian is essentially coincident with the base of the Gzhelian.