Characterization of sills associated with the U reflection on the Newfoundland margin : evidence for widespread early post-rift magmatism on a magma-poor rifted margin

Author Posting. © The Authors, 2010. This article is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 182 (2010): 113-136, doi:10.1111/j.1365-246X.2010.04635.x.Drilling during ODP Leg 210 penetrated two post-rift sills (dated as ∼105.3 and ∼97.8 Ma) in the deep sediments overlying basement of the continent–ocean transition zone on the magma-poor Newfoundland margin. The sill emplacement post-dated the onset of seafloor spreading by at least 7–15 Myr. The shallower of the two sills coincides with the high-amplitude U reflection observed throughout the deep Newfoundland Basin, and strong reflectivity in the sub-U sequence suggests that a number of other sills are present there. In this paper, we use multichannel seismic reflection data and synthetic seismograms to investigate the nature, magnitude and extent of this post-rift magmatism in the deep basin. Features observed in seismic profiles that we attribute to sill injection include high-amplitude reflections with geometries characteristic of intrusions such as step-like aspect; abrupt endings, disruptions and junctions of reflections; finger-like forms; differential compaction around possible loci of magma injection and disruption of overlying sediments by apparent fluid venting. Interpreted sills occur only over transitional basement that probably consists of a mixture of serpentinized peridotite and highly thinned continental crust, and they cover an area of ∼80 000 km2. From analysis of synthetic seismograms, we estimate that sill intrusions may comprise ∼26 per cent of the sub-U high-reflectivity sequence, which yields a crude estimate of ∼5800 km3 for the total volume of sills emplaced by post-rift magmatism. This is significant for a margin usually described as 'non-volcanic'. We discuss competing hypotheses about the source of the magmatism, which is still uncertain.G. Peron-Pinvidic's post-doctoral research at the University of Strasbourg and Woods Hole Oceanographic Institution was supported by TOTAL. B. Tucholke's research was supported by NSF grant OCE0647035. Multichannel seismic field programs that provided much of the data used for this research were supported by NSF grants OCE839085, OCE830823 and OCE9819053

Morpho-tectonic evolution and sedimentary architecture of the iberia ocean-continent transition

La plupart des idées conceptuelles sur l'architecture sédimentaire et l'évolution tectonique des marges passives profondes sont fondées sur des études de rifts continentaux ou de marges proximales. Le problème est que, au contraire des marges distales, ces domaines n'ont subi que de faibles taux d'extension.Le travail de thèse présenté dans ce manuscrit a eu pour but d'analyser plus précisément l'architecture de ces marges distales. Il s'est concentré sur le segment central de la marge ouest Ibérique: la Plaine Abyssale Ibérique Sud (PAIS). J'y ai étudié l'évolution des structures de rifting, spatialement et temporellement, en me basant sur une cartographie détaillée de l'architecture sédimentaire et de socle en 3D sur des profils de sismique réflexion. L'évolution polyphase des processus tectoniques de la phase finale du rifting a pu y être identifiée. Les mécanismes d'extension changent du sud au nord de la PAIS depuis des zones de manteau exhumé par des failles de détachement concaves vers le bas à des demi-grabens classiques formés par le basculement normal de blocs continentaux le long de failles de détachement concaves vers le haut. Sur la base de ces résultats, j'ai pu développer un modèle conceptuel pour l'évolution 3D de la PAIS. Ce modèle suggère une migration générale de l'activité de faille normale vers le futur océan et un changement dans le mode d'extension latéralement à la marge, imagé par un changement de géométrie des structures tectoniques. Ces résultats ont des conséquences importantes pour l'approche théorique de la formation d'une marge passive distale. Par exemple, les concepts de breakup continental et de discordance sédimentaire de breakup, censés caractériser le début de l'accrétion océanique, se révèlent en définitive inadaptés: le rifting est fondamentalement polyphase et poly-processus avec une évolution graduelle vers l'océanisation et non une limite temporelle ou spatiale continent-océan cartographiable.Most of the conceptual ideas concerning sedimentary architecture and tectonic evolution of deep rifted margins are based on either continental rifts or proximal margins, both of which underwent only small amounts of crustal thinning.In my PhD thesis I investigated the sediment and basement architecture of the distal magma-poor rifted margin in the Southern Iberia Abyssal Plain (SIAP). The spatial and temporal evolution of the rifting structures have been studied, based on a detailed mapping of the sedimentary and basement architecture in 3D on seismic reflection profiles. The polyphase evolution of the final phase of rifting has been identified and described. The data suggest that the extensional mechanisms change from south to north within the SIAP from zones of mantle exhumed via downward concave detachment faults to classical half-grabens formed by the normal tilting of continental blocks along upward concave detachment faults. On the base of these results, I developed a 3D conceptual model for the SIAP evolution. This model suggests a general migration of normal fault activity during final break-up towards the future ocean and a change in the fault geometry during final rifting. This 3D evolution of rifting in deep margins is described for the first time and has important implications for the interpretation of seismic sections from OCT as well as for the interpretation of the deformation processes at distal margins. The concepts of continental breakup and the breakup unconformity, supposed to characterise the beginning of oceanic accretion, are not applicable to Iberia-type margins. At these margins, rifting is fundamentally polyphase and includes various modes of extension that evolve and superpose in time and space migrating and finally localizing in the area of final seafloor spreading

Morpho-tectonic evolution and sedimentary architecture of the iberia ocean-continent transition

La plupart des idées conceptuelles sur l'architecture sédimentaire et l'évolution tectonique des marges passives profondes sont fondées sur des études de rifts continentaux ou de marges proximales. Le problème est que, au contraire des marges distales, ceMost of the conceptual ideas concerning sedimentary architecture and tectonic evolution of deep rifted margins are based on either continental rifts or proximal margins, both of which underwent only small amounts of crustal thinning.In my PhD thesis I in

Morphotectonique et architecture sédimentaire de la transition océan-continent de la marge Ibérique

La plupart des idées conceptuelles sur l'architecture sédimentaire et l'évolution tectonique des marges passives profondes sont fondées sur des études de rifts continentaux ou de marges proximales. Le problème est que, au contraire des marges distales, ces domaines n'ont subi que de faibles taux d'extension. Le travail de thèse présenté dans ce manuscrit a eu pour but d'analyser plus précisément l'architecture de ces marges distales. Il s'est concentré sur le segment central de la marge ouest Ibérique: la Plaine Abyssale Ibérique Sud (PAIS). J'y ai étudié l'évolution des structures de rifting, spatialement et temporellement, en me basant sur une cartographie détaillée de l'architecture sédimentaire et de socle en 3D sur des profils de sismique réflexion. L'évolution polyphase des processus tectoniques de la phase finale du rifting a pu y être identifiée. Les mécanismes d'extension changent du sud au nord de la PAIS depuis des zones de manteau exhumé par des failles de détachement concaves vers le bas à des demi-grabens classiques formés par le basculement normal de blocs continentaux le long de failles de détachement concaves vers le haut. Sur la base de ces résultats, j'ai pu développer un modèle conceptuel pour l'évolution 3D de la PAIS. Ce modèle suggère une migration générale de l'activité de faille normale vers le futur océan et un changement dans le mode d'extension latéralement à la marge, imagé par un changement de géométrie des structures tectoniques. Ces résultats ont des conséquences importantes pour l'approche théorique de la formation d'une marge passive distale. Par exemple, les concepts de breakup continental et de discordance sédimentaire de breakup, censés caractériser le début de l'accrétion océanique, se révèlent en définitive inadaptés: le rifting est fondamentalement polyphase et poly-processus avec une évolution graduelle vers l'océanisation et non une limite temporelle ou spatiale continent-océan cartographiable.Most of the conceptual ideas concerning sedimentary architecture and tectonic evolution of deep rifted margins are based on either continental rifts or proximal margins, both of which underwent only small amounts of crustal thinning. In my PhD thesis I investigated the sediment and basement architecture of the distal magma-poor rifted margin in the Southern Iberia Abyssal Plain (SIAP). The spatial and temporal evolution of the rifting structures have been studied, based on a detailed mapping of the sedimentary and basement architecture in 3D on seismic reflection profiles. The polyphase evolution of the final phase of rifting has been identified and described. The data suggest that the extensional mechanisms change from south to north within the SIAP from zones of mantle exhumed via downward concave detachment faults to classical half-grabens formed by the normal tilting of continental blocks along upward concave detachment faults. On the base of these results, I developed a 3D conceptual model for the SIAP evolution. This model suggests a general migration of normal fault activity during final break-up towards the future ocean and a change in the fault geometry during final rifting. This 3D evolution of rifting in deep margins is described for the first time and has important implications for the interpretation of seismic sections from OCT as well as for the interpretation of the deformation processes at distal margins. The concepts of continental breakup and the breakup unconformity, supposed to characterise the beginning of oceanic accretion, are not applicable to Iberia-type margins. At these margins, rifting is fundamentally polyphase and includes various modes of extension that evolve and superpose in time and space migrating and finally localizing in the area of final seafloor spreading

Rifted Margins: State of the Art and Future Challenges

Improvements in seismic imaging, computing capabilities, and analytical methods, as well as a number of industry deep-water wells sampling distal offshore settings, have underpinned new concepts for rifted margin evolution developed in the last two decades; these mark significant progress in our understanding of extensional systems. For example, the tectonic, sedimentary, and magmatic processes linked to the formation of rifted margins have been overhauled, giving rise to more quantitative approaches and new concepts. However, these processes cannot be understood in isolation, requiring consideration of the continuum in which inheritance and physical processes are integrated within a plate tectonic framework. The major progress and fundamental developments of past research in rifted margins have been made hand-in- hand with other domains of Earth Sciences and have fundamental implications for the understanding of key geological systems such as active rifts, the ocean lithosphere, subduction zones, and collisional orogens. The “IMAGinING RIFTING” workshop, organized in Pontresina-Switzerland in September 2017, gathered researchers from all disciplines working on rifts and rifted margins, and included participants from academia and industry. This contribution summarizes the workshop discussions, in addition to outlining our state-of-the-art knowledge of rifted margins. We highlight future challenges in unraveling the processes and conditions under which these extensional systems form and, ultimately, how tectonic plates rupture and new oceans are born. Our aims here are to provide a framework for future research endeavors and to promote collaboration not only within the rift and rifted margins communities, but across other Earth Science disciplines

From orogeny to rifting: insights from the Norwegian ‘reactivation phase’

Based on observations from the Mid-Norwegian extensional system, we describe how, when and where the post-Caledonian continental crust evolved from a context of orogenic disintegration to one of continental rifting. We highlight the importance of a deformation stage that occurred between the collapse mode and the high-angle faulting mode often associated with early rifting of continental crust. This transitional stage, which we interpret to represent the earliest stage of rifting, includes unexpected large magnitudes of crustal thinning facilitated through the reactivation and further development of inherited collapse structures, including detachment faults, shear zones and metamorphic core complexes. The reduction of the already re-equilibrated post-orogenic crust to only ~ 50% of normal thickness over large areas, and considerably less locally, during this stage shows that the common assumption of very moderate extension in the proximal margin domain may not conform to margins that developed on collapsed orogens

Morphotectonique et architecture sédimentaire de la transition océan-continent de la marge ibérique

La plupart des idées conceptuelles sur l'architecture sédimentaire et l'évolution tectonique des marges passives profondes sont fondées sur des études de rifts continentaux ou de marges proximales. Le problème est que, au contraire des marges distales, ces domaines n'ont subi que de faibles taux d'extension.Le travail de thèse présenté dans ce manuscrit a eu pour but d'analyser plus précisément l'architecture de ces marges distales. Il s'est concentré sur le segment central de la marge ouest Ibérique: la Plaine Abyssale Ibérique Sud (PAIS). J'y ai étudié l'évolution des structures de rifting, spatialement et temporellement, en me basant sur une cartographie détaillée de l'architecture sédimentaire et de socle en 3D sur des profils de sismique réflexion. L'évolution polyphase des processus tectoniques de la phase finale du rifting a pu y être identifiée. Les mécanismes d'extension changent du sud au nord de la PAIS depuis des zones de manteau exhumé par des failles de détachement concaves vers le bas à des demi-grabens classiques formés par le basculement normal de blocs continentaux le long de failles de détachement concaves vers le haut. Sur la base de ces résultats, j'ai pu développer un modèle conceptuel pour l'évolution 3D de la PAIS. Ce modèle suggère une migration générale de l'activité de faille normale vers le futur océan et un changement dans le mode d'extension latéralement à la marge, imagé par un changement de géométrie des structures tectoniques. Ces résultats ont des conséquences importantes pour l'approche théorique de la formation d'une marge passive distale. Par exemple, les concepts de breakup continental et de discordance sédimentaire de breakup, censés caractériser le début de l'accrétion océanique, se révèlent en définitive inadaptés: le rifting est fondamentalement polyphase et poly-processus avec une évolution graduelle vers l'océanisation et non une limite temporelle ou spatiale continent-océan cartographiable.Most of the conceptual ideas concerning sedimentary architecture and tectonic evolution of deep rifted margins are based on either continental rifts or proximal margins, both of which underwent only small amounts of crustal thinning.In my PhD thesis I investigated the sediment and basement architecture of the distal magma-poor rifted margin in the Southern Iberia Abyssal Plain (SIAP). The spatial and temporal evolution of the rifting structures have been studied, based on a detailed mapping of the sedimentary and basement architecture in 3D on seismic reflection profiles. The polyphase evolution of the final phase of rifting has been identified and described. The data suggest that the extensional mechanisms change from south to north within the SIAP from zones of mantle exhumed via downward concave detachment faults to classical half-grabens formed by the normal tilting of continental blocks along upward concave detachment faults. On the base of these results, I developed a 3D conceptual model for the SIAP evolution. This model suggests a general migration of normal fault activity during final break-up towards the future ocean and a change in the fault geometry during final rifting. This 3D evolution of rifting in deep margins is described for the first time and has important implications for the interpretation of seismic sections from OCT as well as for the interpretation of the deformation processes at distal margins. The concepts of continental breakup and the breakup unconformity, supposed to characterise the beginning of oceanic accretion, are not applicable to Iberia-type margins. At these margins, rifting is fundamentally polyphase and includes various modes of extension that evolve and superpose in time and space migrating and finally localizing in the area of final seafloor spreading.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Insights from the Jan Mayen system in the Norwegian-Greenland Sea-II. Architecture of a microcontinent

We study the formation and evolution of the Jan Mayen microcontinent (JMMC) in the framework of conjugate margin evolution in the Norwegian-Greenland Sea. The JMMC structural map and crustal architecture have been constrained by seismic mapping and potential field modelling, supplemented by published seismic refraction transects. The sedimentary and basement geometries have been further studied together with their conjugate to refine our knowledge on the less explored microcontinent. Structurally, the JMMC main ridge is characterized by a platform and/or terrace architecture flanked by sag type basins, similar to those described on the mid-Norwegian conjugate margin, while its southern part is marked by windows exposing crustal and/or mantle material that was exhumed during higher degrees of extension. The eastern side of the JMMC broke up in a magma-rich fashion, while the western side is magma poor. The limited amount of magma involved in the JMMC formation suggests that changes in far field forces were the driving mechanism to initiate the isolation process and that a mantle plume had a lesser influence, but might have helped the final mid-ocean ridge establishment between the western Jan Mayen and Greenland margin.</p

Insights from the Jan Mayen system in the Norwegian-Greenland sea-I. Mapping of a microcontinent

In this contribution, we present a model of microcontinent architecture within a system that involves a complex rifted margin setting and different phases of deformation and continental breakup. Our case study is the Jan Mayen Microcontinent (JMMC) located in the central part of the Norwegian-Greenland Sea. We have revised its basement and sedimentary geometries using modern and vintage seismic reflection profiles, and updated potential field data. The northern part of the JMMC consists of a ∼10-15 km thick continental crust body flanked by two major sedimentary basins. We propose that the microcontinent is divided into six distinct segments, characterized by different basement and sedimentary architectures. The shallow stratigraphy is well imaged and has been detailed. Three distinct sedimentary units have been defined together with pronounced reflectors (JA, Red, JO and F), related to erosional, magmatic, thermal or uplift events. The continent-ocean boundary has been revised together with the mapping of the distinct volcanic events that characterize the evolution of the microcontinent. A companion paper aims to further detail the interpretation of the JMMC structure presented here by constraining the conjugated mid-Norwegian and mid-East Greenland structures.</p

Rifting continents

Continental rifts can form when and where continents are stretched. If the driving forces can overcome lithospheric strength, a rift valley forms. Rifts are characterized by faults, sedimentary basins, earthquakes, and/or volcanism. With the right set of weakening feedbacks, a rift can evolve to break a continent into conjugate rifted margins such as those found along the Atlantic and Indian Oceans. When, however, strengthening processes overtake weakening, rifting can stall and leave a failed rift, such as the North Sea or the West African Rift. A clear definition of continental breakup is still lacking because the transition from continent to ocean can be complex, with tilted continental blocks and regions of exhumed lithospheric mantle. Rifts and rifted margins not only shape the face of our planet, they also have a clear societal impact, through hazards caused by earthquakes, volcanism, landslides, and CO2 release, and through their resources, such as fertile land, hydrocarbons, minerals, and geothermal potential. This societal relevance makes an understanding of the many unknown aspects of rift processes as critical as ever.</p