Cenozoic postrift domal uplift of North Atlantic margins: An asthenospheric diapirism model

Postrift domal uplifts are a distinct feature of the northern North Atlantic rifted margins. Uplifted regions (southern Norway, Finnmark, Svalbard, northern United Kingdom) occur with a typical spacing of ∼ 900 km. The amount of domal uplift is substantial (1 2 km); thermochronological, geomorphological, and seismic stratigraphic data suggest a coincident Neogene onset of uplift, postdating North Atlantic breakup and predating onset of glaciation. The Norwegian domes are characterized by strongly negative gravity anomalies and reduced mantle P-wave and S-wave velocities. Previous models for uplift around the North Atlantic (e.g., glacial erosion, intraplate stresses, secondary convection) fail to explain the above characteristics. We present an asthenospheric diapir model based on a Rayleigh-Taylor instability, wherein a hot “Icelandic” asthenosphere layer meets cold cratonic lithosphere. The generated asthenospheric diapirs and associated partial melting offer a viable explanation for updoming. Application of this model to the south Norwegian dome succesfully explains most of the currently available data.