The Norwegian Margin formed in response to early Cenozoic continental breakup and subsequent opening of the Norwegian-Greenland Sea. There is a welldefined margin segmentation and the various segments are characterized by distinct crustal properties, structural and magmatic styles, and post-opening history of vertical motions. The sedimentary basins at the conjugate continental margins off Norway and Greenland and in the western Barents Sea developed as a result of a series of post-Caledonian rift episodes until early Cenozoic time, when complete continental separation took place.

[1] Seismic reflection and refraction profiles, and potential field data, complemented by crustal-scale gravity modeling and plate reconstructions are used to study the evolution of the central and south segments of the South Atlantic conjugate margins. The central segment is characterized by a hyperextended continent-ocean transitional domain that shows evidence of rotated fault blocks and a detachment surface active during rifting. A polyphase rifting evolution mode, associated with a complex time-dependent thermal structure of the lithosphere, is substantiated for the central segment that is not a "magma-poor" end-member. Increase of volcanic activity during the late stages of rifting may have "interrupted" the extensional system implying a failed exhumation phase that was replaced instead by continental breakup and emplacement of fully igneous crust. The continent-ocean transitional domain along the "magma-dominated" south segment is characterized by a large volume of flood basalts and high-velocity/high-density lower crust. The northern province of the south segment is characterized by symmetrical seaward-dipping reflections and symmetrical continent-ocean transitional domain. The influence of the Tristan da Cunha plume on this province is very likely. The central province of the south segment is characterized by along-strike tectonomagmatic asymmetry, which can be caused by the initial continental stretching and accompanying magmatism rather than by the subsequent seafloor spreading. The Tristan da Cunha plume on the central province may have influenced the volume of magmatism but did not necessarily alter the process of rifted margin formation, implying that the central province of the south segment may have much in common with "magma-poor" margins.

Voluminous volcanism characterized Early Tertiary continental break-up on the mid-Norwegian continental margin. The distribution of the associated extrusive rocks derived from seismic volcanostratigraphy and potential field data interpretation allows us to divide the Møre, Vøring and Lofoten-Vesterålen margins into five segments. The central Møre Margin and the northern Vøring Margin show combinations of volcanic seismic facies units that are characteristic for typical rifted volcanic margins. The LofotenVesterålen Margin, the southern Vøring Margin and the area near the Jan Mayen Fracture Zone show volcanic seismic facies units that are related to small-volume, submarine volcanism. The distribution of subaerial and submarine deposits indicates variations of subsidence along the margin. Vertical movements on the mid-Norwegian margin were primarily controlled by the amount of magmatic crustal thickening, because both the amount of dynamic uplift by the Icelandic mantle plume and the amount of subsidence due to crustal stretching were fairly constant along the margin. Thus, subaerial deposits indicate a large amount of magmatic crustal thickening and an associated reduction in isostatic subsidence, whereas submarine deposits indicate little magmatic thickening and earlier subsidence. From the distribution of volcanic seismic facies units we infer two main reasons for the different amounts of crustal thickening: (1) a general northward decrease of magmatism due to increasing distance from the hot spot and (2) subdued volcanism near the Jan Mayen Fracture Zone as a result of lateral lithospheric heat transport and cooling of the magmatic source region. Furthermore, we interpret small lateral variations in the distribution of volcanic seismic facies units, such as two sets of Inner Seaward Dipping Reflectors on the central Vøring Margin, as indications of crustal fragmentation.

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S U M M A R YIntegration of regional seismic reflection and refraction profiles and potential field data across the Argentine margin and its conjugate off South Africa, complemented by crustal-scale gravity modelling, is used to reveal and illustrate the whole-crust architecture, onshore-offshore crustal structure correlations, the character of the continent-ocean boundary/transition and the relationship of crustal structure to regional variation of potential field anomalies. The study reveals, within these two provinces, distinct along-margin structural and magmatic changes that are spatially related to a number of conjugate transfer systems governing the margin segmentation and evolution, clearly implying structural inheritance. In particular, the Colorado transfer system on the Argentina margin, marks a distinct along-margin boundary in the distribution and volume of breakup-related magmatism. Similarly, the Hope transfer system on the conjugate South Africa margin also marks a distinct along-margin transition from a zone of relative magnetic quiescence to a zone of prominent magnetic anomalies. Furthermore, the study indicates that the 'G-magnetic anomaly' along the South Africa margin probably defines the eastern limit of the continent-ocean transition (COT) rather than a discrete continentocean boundary (COB). Potential field plate reconstructions of the South Atlantic suggest conjugate margin asymmetry, characterized by a rather broad Argentine margin conjugate to a narrow South Africa margin. In detail, the Argentine margin is characterized by a sharp and relatively constant COT, whereas the COT along the conjugate South Africa margin is considerably wider. An along-strike tectonomagmatic asymmetry variation is also observed and is expressed by the northward increase in width of the COT on the South African margin. The study clearly shows that integration of regional seismic reflection and refraction profiles, potential field data and gravity modelling provide a powerful resource for testing and validating alternative seismic profile structural interpretations and plate tectonic reconstructions, as well as geodynamic models for lithospheric breakup and early drift.

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