Regional investigations and hydrocarbon exploration history. South atlantic rifting and some general principles for rift exploration on continental margins ian davison1 and eoin o. These margins are active tectonically and have less width and sediment input than passive margins. As the archetype atlanticstyle passive margin, the postrift morphology of the usam prior to the neogene appears to have been characterized by. The continental margins and continental shelf mark lower density, but greater thickness felsic continental rock that often much older than that of the seafloor. From this time onward, the subsidence of the continental margin is. Atlantic rifts and continental margins geophysical. Plateau eastern north atlantic margins were underlain by tilted and rotated. Manik talwani and vitor abreu, inferences regarding initiation of oceanic crust formation from the u.
The importance of rift history for volcanic margin formation. The north atlantic margins exhibit a full range of magmatic behaviour. Thus, depending on the source rocks and the geological setting, the compositions of the sulfide deposits can vary considerably. There can be as much as 15 km of mesozoic and later sediments at some continental margins bordering the n. 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. 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. Basin evolution, configuration styles, and hydrocarbon. Indications of widespread glaciation from 380 to 250 million years ago are evident in antarctica, southern south america, southern africa, india, and australia. A continental margins, midocean ridges, and deepocean basins b midocean ridges, continental shelves, and divergent boundaries c submarine trenches, midocean ridges, and turbidity currents d deepocean basins, active margins, and passive margins. 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. Lowercrustal intrusion on the north atlantic continental.
Lowercrustal intrusion on the north atlantic continental margin. Alphabetical list of all rifts spells, and their page numbers in the rifts book of magic. 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. 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. Pdf atlantic and gulf of mexico continental margins.
This possibility has been suggested for the south atlantic margins. Atlantic and gulf of mexico continental margins chapter pdf available in memoir of the geological society of america memoir 172chapter 17. Crustal structure and magmatism of north atlantic continental. A passive margin is the transition between oceanic and continental lithosphere that is not an active plate margin. Architecture of rifted continental margins and breakup evolution.
The oldest oceanic crust in the atlantic is up to 145 million years and situated off the west coast of africa and east coast of north america, or on either side of the south atlantic. 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. Atlantic rifts and continental margins geophysical monograph. One aspect of continental margins that has always been puzzling is the existence of very thick but relatively shallowwater sedimentary sequences. New techniques have stimulated recent improvements in conceptual models that integrate geological and geophysical methods for interpreting deep water regions.
It has been said that the idea of rigid areas rifting. Af continental margins and the slow birth of an ocean 6 june 2014 a newborn ocean. The conjugate margins of eastern south america and western africa are marked by two tectonic styles. Atlantic rifts and continental margins fills a major information gap in the seismic documentation of the passive margins of the atlantic basin.
The mesozoic south atlantic ocean and evolution of its. 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. A passive margin forms by sedimentation above an ancient rift, now marked by transitional lithosphere. Today, the theory of continental drift has been replaced by the science of plate tectonics. The preexisting faults can be transform faults or step. Early evolution of the south atlantic ocean deep sea drilling. 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. A comparison of two atlantictype continental margins. Active continental margins, where plates are converging, coincide with plate boundaries, where the continental and oceanic crust are separated by a subduction zone. 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. Since no tectonic activity happens along such continental margins after. 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. The west africa continental margin acts as an active hinge zone between the uplifting continent and the subsiding ocean.
Learn vocabulary, terms, and more with flashcards, games, and other study tools. At some margins massive outpouring of igneous material occurs, whilst at others there is almost none. 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. A comparison of two atlantictype continental margins usgs. In the early 20th century, wegener published a paper explaining. The crustal structure across the transform continental. Only few tenths of kilometres separate the massive rift shoulders of the sinai. Mapping palaeostructure and palaeobathymetry along the. 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. 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. 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. Rowan, in permotriassic salt provinces of europe, north africa and the atlantic margins, 2017. South atlantic margin rift basin asymmetry and implications. 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.
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. Ne atlantic continental rifting and volcanic margin formation. Pdf 3 models for the evolution of passive margins researchgate. South atlantic rifting and some general principles for. Rifting, seafloor spreading, and extensional tectonics. L accumulation des sediments postrift sur une marge continentale represente une charge. 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. 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.
Rifts formed in old, cold, strong shields tend to be narrow, while rifts formed in young, warm, soft orogens tend to be wide. Rift asymmetry and continental uplift wiley online library. 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. Continental rifts which are likely to evolve into passive margins with time contain another 30% of the worlds giant oil fields. The passive continental margins bordering the ocean basin are underlain by stretched continental crust.
East coast margin and conjugate south atlantic margins, atlantic rifts and continental margins, 211233, 20. The theory of continental drift is most associated with the scientist alfred wegener. Midocean ridge deposits associated with nmorb are typi. Evolution of continental rift systems in the light of plate. Atlantic rifts and continental margins structural geology. 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.
Enormous variations exist along rifted margins of the north atlantic in the magmatic activity that accompanied continental breakup. South atlantic continental margins of africa arxiv. Along its two coasts, 25 passive continental margin basins have been explored, 80% basins are in deepwater setting. Atlantic rifts and continental margins request pdf. Subsidence and tectonics of atlantic type continental margins. 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. 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. South atlantic rifting and some general principles for rift. Continental drift describes one of the earliest ways geologist s thought continent s moved over time. Ultimate edition will be current and up to date with the. 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 nonlinear interaction between key parameters such as plate boundary con. 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. These stresses were dissipated into intracontinental rifts in west africa and northeast brazil fairhead and binks, 1991.
Basins associated with collision zones and subduction zones are where most of the remaining giant oil fields are found. Keys to understanding the process of continental breakup and its relation to preexisting. The crustal structure across the transform continental margin. 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. Eventually the continental rift forms a midocean ridge and the locus of extension moves away from the continentocean. 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. Ne atlantic continental rifting and volcanic margin formation article in geological society london special publications 1671. Geodiversity of hydrothermal processes along the midatlantic. Some of the worlds most spectacular salt structures are located on saltbearing, passive continental margins, such as offshore northern egypt gaullier et al. Atlantic rift allows to link changes in relative plate velocities and direction. Rift basins have been increasingly the focus of research in tectonics, structural geology, and basin analysis. Jun 17, 2010 continental breakup is accompanied by highly variable amounts of magmatism.
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