Search

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 the Palacozoic to the Cretaceous, crustal thinning in the Mid Norway area was associated with the denudation of gneiss-cored culminations and metamorphic core complexes in the footwalls of major extensional faults. The development of the culminations led to warping and deactivation of early detachments, to the nucleation of new faults in more distal positions and to the exhumation of highgrade metamorphic rocks to more shallow levels in the crust. Some of the culminations and core complexes became part of the erosional template in Mid-Late Palaeozoic time, some were probably exhumed in the Mesozoic, whereas some may never have reached the surface. We present an overview of five types of gneiss-cored culminations and core complexes that have been identified in the field, through the interpretation of offshore, long-offset seismic reflection data. We furthermore address their mechanism(s) of formation, and their role in the progressive evolution of the Mid-Norwegian margin.

Combining information from onshore and offshore Mid-Norway, we propose a structural model for the Scandinavian North Atlantic passive margin from Permo- Carboniferous through Present. We re-examine the role of post-Permo-Carboniferous normal faults and define an innermost boundary fault system forming the continentward limit of the rifted margin. Crustal-scale cross-sections of the Greenland- Norway passive margins show the asymmetric nature of crustal extension between the two conjugate margins. On both margins the upper plate/lower plate geometry and the dip of major extensional normal faults change across the broad width of the Jan Mayen Fracture Zone. South of this zone on the Møre Margin (Norway), the dip of the major faults is towards the west, defining a lower plate – tilted block margin. North of the transform on the Vøring-Trøndelag Margin (Norway), the major faults dip to the east, defining an upper plate or flexural margin. In the Norwegian passive margin, the transition occurs as a progressive change of vergence of normal faults between the northern Vøring-Trøndelag Platform area and the Møre Basin. The model shows continuous separation between the two conjugate margins of Greenland and Norway, starting with a very tight fit in Late Permian time. The rifting events between Late Permian and Late Cretaceous are associated with a broadly WSW-ENE- to W-E- oriented extension while Late Cretaceous to Early Tertiary extension directions are oriented NNW-SSE. These plate separation directions and the subsequent plate motion can be related to the important basin development within, and probably, to the structural evolution and geometry of, the conjugate passive margins.

From the Palacozoic to the Cretaceous, crustal thinning in the Mid Norway area was associated with the denudation of gneiss-cored culminations and metamorphic core complexes in the footwalls of major extensional faults. The development of the culminations led to warping and deactivation of early detachments, to the nucleation of new faults in more distal positions and to the exhumation of highgrade metamorphic rocks to more shallow levels in the crust. Some of the culminations and core complexes became part of the erosional template in Mid-Late Palaeozoic time, some were probably exhumed in the Mesozoic, whereas some may never have reached the surface. We present an overview of five types of gneiss-cored culminations and core complexes that have been identified in the field, through the interpretation of offshore, long-offset seismic reflection data. We furthermore address their mechanism(s) of formation, and their role in the progressive evolution of the Mid-Norwegian margin.

Combining information from onshore and offshore Mid-Norway, we propose a structural model for the Scandinavian North Atlantic passive margin from Permo- Carboniferous through Present. We re-examine the role of post-Permo-Carboniferous normal faults and define an innermost boundary fault system forming the continentward limit of the rifted margin. Crustal-scale cross-sections of the Greenland- Norway passive margins show the asymmetric nature of crustal extension between the two conjugate margins. On both margins the upper plate/lower plate geometry and the dip of major extensional normal faults change across the broad width of the Jan Mayen Fracture Zone. South of this zone on the Møre Margin (Norway), the dip of the major faults is towards the west, defining a lower plate – tilted block margin. North of the transform on the Vøring-Trøndelag Margin (Norway), the major faults dip to the east, defining an upper plate or flexural margin. In the Norwegian passive margin, the transition occurs as a progressive change of vergence of normal faults between the northern Vøring-Trøndelag Platform area and the Møre Basin. The model shows continuous separation between the two conjugate margins of Greenland and Norway, starting with a very tight fit in Late Permian time. The rifting events between Late Permian and Late Cretaceous are associated with a broadly WSW-ENE- to W-E- oriented extension while Late Cretaceous to Early Tertiary extension directions are oriented NNW-SSE. These plate separation directions and the subsequent plate motion can be related to the important basin development within, and probably, to the structural evolution and geometry of, the conjugate passive margins.