Ne atlantic continental rifting and volcanic margin formation. The generation of volcanic continental margins and flood basalts robert white and dan mckenzie bullard laboratories, department of earth sciences, cambridge, enyland when continents rift to form new ocean basins, the riftingis sometimes accompanied by mas sive igneous activity. Mar 27, 2008 highvelocity lower crust is now known to be ubiquitous on volcanic continental margins, including all those in the northern north atlantic 3,4,5,6,7,8,9,10,11. The crustal structure across the transform continental. Thus, depending on the source rocks and the geological setting, the compositions of the sulfide deposits can vary considerably. Midocean ridge deposits associated with nmorb are typi. Atlantic rifts and continental margins request pdf. Pdf 3 models for the evolution of passive margins researchgate. Atlantic was the locus of intersection of the central and south atlantic rifts, and therefore had to accommodate the stresses arising from the differential opening of these two ocean basins. South atlantic rifting and some general principles for. Plateau eastern north atlantic margins were underlain by tilted and rotated. These margins are active tectonically and have less width and sediment input than passive margins.
Rift basins have been increasingly the focus of research in tectonics, structural geology, and basin analysis. Mapping palaeostructure and palaeobathymetry along the. From this time onward, the subsidence of the continental margin is. South atlantic margin rift basin asymmetry and implications. Atlantic rifts and continental margins geophysical monograph. Geophysics copyright 2020 lateral propagationinduced. Subsidence and tectonics of atlantic type continental margins. The conjugate margins of eastern south america and western africa are marked by two tectonic styles. Atlantic rift allows to link changes in relative plate velocities and direction. Rift deposition pink persisted in rifts and on ocean floor, under air, till sea water spilled in to form evaporites at 112 ma late aptian after evaporites were deposited, carbonate deposition blue followed ending at 2040.
One end of the spectrum commonly termed volcanic margins is found in the northern north atlantic off greenland, norway and northwest britain, where huge volumes of igneous rock were. Request pdf atlantic rifts and continental margins in compiling this volume, we have aimed to develop and enhance our current understanding of the structural evolution and sedimentation. The passive continental margins bordering the ocean basin are underlain by stretched continental crust. Eventually the continental rift forms a midocean ridge and the locus of extension moves away from the continentocean. Along its two coasts, 25 passive continental margin basins have been explored, 80% basins are in deepwater setting. In compiling this volume, we have aimed to develop and enhance our current understanding of the structural evolution and sedimentation processes along divergent continental margins. A comparison of two atlantictype continental margins usgs.
Atlantic and gulf of mexico continental margins are thickly sedimented passive margins that formed when pangea split apart during middle jurassic time to create the atlantic ocean and gulf of mexico. A the equatorial atlantic margin basins that essentially result from the breakup slippage along an extensive eastwest system of linear fractures extending from oceanic crust towards the margin. Today, the theory of continental drift has been replaced by the science of plate tectonics. Atlantic rifts and continental margins geophysical. A passive margin forms by sedimentation above an ancient rift, now marked by transitional lithosphere. Ultimate edition will be current and up to date with the. Atlantic rifts and continental margins fills a major information gap in the seismic documentation of the passive margins of the atlantic basin. Rifting between large continental plates results in either continental breakup and the for mation of conjugate passive margins, or rift abandonment and a set of aborted rift basins. Keys to understanding the process of continental breakup and its relation to preexisting. The red sea and gulf of aden sedimentary basins are developed along the african and arabian conjugate margins and are characterized by late tertiary rifts filled with siliciclastic, carbonate, and thick evaporite successions north of the babelmandeb strait in the red sea. The west africa continental margin acts as an active hinge zone between the uplifting continent and the subsiding ocean. Triassic, forming a number of rift basins that are located onshore and. Since no tectonic activity happens along such continental margins after.
Af continental margins and the slow birth of an ocean 6 june 2014 a newborn ocean. Only few tenths of kilometres separate the massive rift shoulders of the sinai. A passive margin is the transition between oceanic and continental lithosphere that is not an active plate margin. The north atlantic margins exhibit a full range of magmatic behaviour. Geodiversity of hydrothermal processes along the midatlantic. Jan 01, 2000 atlantic rifts and continental margins fills a major information gap in the seismic documentation of the passive margins of the atlantic basin. In the early 20th century, wegener published a paper explaining. Plate movements and the basic difference in the density of oceanic and continental crustal units initiate the structural pattern of continental margins and result in a tectonic classification of coastlines as active pacific, leading edge or passive atlantic, trailing edge margins, each of which have. Kinematics of the south atlantic and its continental margins are strongly dependent upon the understanding of the relationships between rifting and the tristan da cunha hot spot. New techniques have stimulated recent improvements in conceptual models that integrate geological and geophysical methods for interpreting deep water regions. Eleven classes of rifts with diverse histories can be distinguished among the rifts presently facing atlantic type continental margins and aulacogen histories are even more diverse.
Atlantic and gulf of mexico continental margins chapter pdf available in memoir of the geological society of america memoir 172chapter 17. L accumulation des sediments postrift sur une marge continentale represente une charge. As the archetype atlanticstyle passive margin, the postrift morphology of the usam prior to the neogene appears to have been characterized by. Continental rifts which are likely to evolve into passive margins with time contain another 30% of the worlds giant oil fields. South atlantic rifting and some general principles for rift. Highvelocity lower crust is now known to be ubiquitous on volcanic continental margins, including all those in the northern north atlantic 3,4,5,6,7,8,9,10,11. Such diversity is caused by a fundamental underlying structural asymmetry, derived from each basins distinct rift, continental margin breakup, and drift phases in its history. Crustal structure and magmatism of north atlantic continental. The connection of continental drift with the construction of major mountain ranges will be revealed, and finally we will discuss the closely connected polar wander and the measurement of continual continental movements. Passive margins include the conjugatemargin pairs of morocco and nova scotia upper triassic to lower jurassic salt, western iberia and newfoundland sameage salt, and the southwestern barents sea and northeast greenland pennsylvanian to lower permian salt. Rifting, seafloor spreading, and extensional tectonics. These stresses were dissipated into intracontinental rifts in west africa and northeast brazil fairhead and binks, 1991. The continental margins and continental shelf mark lower density, but greater thickness felsic continental rock that often much older than that of the seafloor. Architecture of rifted continental margins and breakup evolution.
Alphabetical list of all rifts spells, and their page numbers in the rifts book of magic. Indications of widespread glaciation from 380 to 250 million years ago are evident in antarctica, southern south america, southern africa, india, and australia. Pdf atlantic and gulf of mexico continental margins. Basins associated with collision zones and subduction zones are where most of the remaining giant oil fields are found. South atlantic continental margins of africa arxiv. The theory of continental drift is most associated with the scientist alfred wegener. Rifts formed in old, cold, strong shields tend to be narrow, while rifts formed in young, warm, soft orogens tend to be wide. The crustal structure across the transform continental margin. To counteract the unfortunate situation of a lack of modern seismic and potential fields data on circum atlantic passive margins in the literature, we have linked new data from oil companies with that of research. Regional investigations and hydrocarbon exploration history. The preexisting faults can be transform faults or step. Eleven mapped horizons from seabed to the base cretaceous have been sequentially backstripped to produce a suite of palaeobathymetry and palaeostructure maps for all horizons at all time stages. Lowercrustal intrusion on the north atlantic continental margin.
Evolution of continental rift systems in the light of plate. Early evolution of the south atlantic ocean deep sea drilling. The importance of rift history for volcanic margin formation. There can be as much as 15 km of mesozoic and later sediments at some continental margins bordering the n.
South atlantic rifting and some general principles for rift exploration on continental margins ian davison1 and eoin o. In many ways the best known of rift systems are those formed at the opening of the atlantic ocean because they have been subjected to intense petroleum exploration. It has been said that the idea of rigid areas rifting. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Jun 17, 2010 continental breakup is accompanied by highly variable amounts of magmatism. Mar 12, 2020 aside from the congruency of continental shelf margins across the atlantic, modern proponents of continental drift have amassed impressive geologic evidence to support their views. Rowan, in permotriassic salt provinces of europe, north africa and the atlantic margins, 2017. Ne atlantic continental rifting and volcanic margin formation article in geological society london special publications 1671. A comparison of two atlantictype continental margins.
Lowercrustal intrusion on the north atlantic continental. One aspect of continental margins that has always been puzzling is the existence of very thick but relatively shallowwater sedimentary sequences. East coast margin and conjugate south atlantic margins, atlantic rifts and continental margins, 211233, 20. The mesozoic south atlantic ocean and evolution of its. Rift asymmetry and continental uplift wiley online library. Continental margins can be characterized as of atlantic or pacific type, essentially depending on whether they have experienced a relatively long period of stability, in which case they are called atlantic type, or whether they have suffered active tectonism during latter geological times, in which case they are assigned to the pacific type. The nonlinear interaction between key parameters such as plate boundary con. At some margins massive outpouring of igneous material occurs, whilst at others there is almost none. Atlantic rifts and continental margins structural geology. Manik talwani and vitor abreu, inferences regarding initiation of oceanic crust formation from the u.
Abstract the postjurassic bathymetric and subsidence history of the midnorwegian atlantic margin more and voring basins has been investigated using the technique of 3dflexural backstripping. This possibility has been suggested for the south atlantic margins. Africa is more uplifted in the central southern part, east of the cretaceous atlantic ocean, whereas the northern part of the continent, with a lower topography, is located eastward of the oldest jurassic part of the atlantic. Enormous variations exist along rifted margins of the north atlantic in the magmatic activity that accompanied continental breakup. Basin evolution, configuration styles, and hydrocarbon.
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