Extensional crustal tectonics and crust-mantle coupling, a view from the geological record

摘要: We present here a number of geological observations in extensional contexts, either continental rifts or back-arcs, that show different situations potential coupling between asthenospheric flow and crustal deformation. Several these examples deformation distributed over hectometre to kilometre thick shear zones, accommodated by shallow dipping zones with constant asymmetry large distances. This is the case Mediterranean back-arc basins, such as Aegean Sea, northern Tyrrhenian Alboran domain Gulf Lion passive margin. Similar types observation can be made on some South Atlantic volcanic margins Afar region, which were formed above mantle plume. In all lithosphere hot lithospheric thin possibly absent. discuss contexts main controlling parameters for this asymmetrical implies simple component at scale lithosphere. These include an original heterogeneity crust (tectonic heritage), lateral density gradients contribution underlying through basal drag push. relations observed direction sense underneath. The chosen suggest two mechanisms explain asymmetry: (1) shearing parallel Moho necking zone during rifting (2) viscous basins plumes. Slipping along pre-existing heterogeneities seems second-order phenomenon scale.