Abstract
Lithospheric extension can generate passive margins that bound oceans worldwide. Detailed geological and geophysical studies in present and fossil passive margins have highlighted the complexity of their architecture and their multi-stage deformation history. Previous modeling studies have shown the significant impact of coarse mechanical layering of the lithosphere (2 to 4 layer crust and mantle) on passive margin formation. We built upon these studies and design high-resolution (~100–300 m) thermo-mechanical numerical models that incorporate finer mechanical layering (kilometer scale) mimicking tectonically inherited heterogeneities. During lithospheric extension a variety of extensional structures arises naturally due to (1) structural softening caused by necking of mechanically strong layers and (2) the establishment of a network of weak layers across the deforming multi-layered lithosphere. We argue that structural softening in a multi-layered lithosphere is the main cause for the observed multi-stage evolution and architecture of magma-poor passive margins.
Highlights
Lithospheric extension can generate passive margins that bound oceans worldwide
We argue that structural softening in a multi-layered lithosphere is the main cause for the observed multi-stage evolution and architecture of magma-poor passive margins
Passive continental margins are the focus of intense research activity since decades[1,2,3], enhanced by the intensification of both industrial and academic geophysical surveys associated with ocean drilling programs (ODP)
Summary
(4) development of anastomosing shear zones in weak layers acting as décollement levels and accommodating the lateral extraction of strong layers, (5) low-angle detachment faults exhuming the subcontinental mantle and accompanying the formation of crustal allochthons. Most of these structures have been identified on land[38,39] and offshore[35,40,41], their significance and interplay are debated. Future models will allow resolving even finer structures and associated softening, in the aim of further refining our knowledge about passive margin forming processes
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