The east greenland caledonides - Teleseismic signature, gravity and isostasy

Abstract

The large-scale geological evolution of the North Atlantic Realm during the past 450 Myr is largely understood, but crucial elements remain uncertain. These involve the Caledonian orogeny, the formation of the North Atlantic and accompanying igneous activity, and the present-day high topography surrounding the North Atlantic. Teleseismic receiver function interpretation in the Central Fjord Region of East Greenland recently suggested the presence of a fossil Caledonian subduction complex, including a slab of eclogitised mafic crust and an overlying wedge of serpentinised mantle peridotite. Here we further investigate this topic using inverse receiver functions modelling. The obtained velocity models are tested with regard to their consistency with the regional gravity field and topography. We find that the obtained receiver function model is generally consistent with gravity and isostasy. The western part of the section, with topography of >1000 m, is clearly supported by the 40-km-thick crust. The eastern part requires additional buoyancy as provided by the hydrated mantle wedge. The geometry, velocities and densities are consistent with interpretation of the lithospheric structure as a fossil subduction zone complex. The spatial relations with Caledonian structures suggest a Caledonian origin. The results indicate that topography is isostatically compensated by density variations within the lithosphere, and that significant dynamic topography is not required at the present-day.