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Interaction of Crustal Structures and Geodynamics on Passive Margin Evolution: Insights From Manet Ridge, Norway

Abstract

Our understanding of rift basins has advanced significantly over the past decade and this has led to a much improved understanding of spatial and temporal fault geometry and the sedimentary evolution of the associated basin fill. Yet, much of this understanding still assumes a homogenous crust with uniform stretching and often does not account for either crustal heterogeneity or differential crustal stretching. One of the best documented examples of the reactivation and subsequent crustal stretching of a continental thrust belt is the mid-Norwegian Margin. It has, during its long tectonic history, undergone both orogenic compressions as well as rift-related extension associated with the Caledonian orogeny, the failed North Sea rift and the eventual Atlantic rift system. The accumulated effect of these events has been a complex evolution of the continental crust and the development of enigmatic structural geometry. Of particular note is the presence of triangular fault-bound rift sequences juxtaposed against significant post-rift sedimentary packages. Through a series of regional transects, and structural restorations, we consider the evolution of the Møre Basin, with particular focus on the Manet Ridge. We consider how much influence the Caledonian orogeny has on the margin and whether subsequent hyperextension has played a role in the area's structural development. The study suggests that the large scale rifting events of the region are related to the crustal inheritance of a NNE to NE-trending Caledonide fabric. The Møre Basin has developed with an established NE trend, but shows evidence of oblique fault overprinting in response to the Atlantic rift. This overprinting is key in the evolution of the Manet Ridge, previously believed to have been structurally initiated in the Jurassic. This study hypothesis an earlier, Triassic origin and an evolution that is more affected by the regional tectonics than previously thought. This study, therefore, provides an excellent example of a multi-phase basin development and highlights the need to understand structural and geodynamic process on passive margins.