The early to middle Miocene tectonic phase in the NE Atlantic

Category Tectonic & Seismotectonic
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Lundin, Erik۱; Doré, Anthony۲; Henriksen, Sverre۱
Holding Date 11 October 2008

The Early to Middle Miocene marked a time of significant tectonic change in the NE Atlantic and the bordering continental margins. In terms of plate tectonics this represents the time when the Arctic gateway via the Fram Strait opened, permitting cold water to enter the Norwegian-Greenland Sea from the Arctic. At the same time the Greenland - Faroes Ridge was breached at the Faroes Conduit as well as at the Denmark Strait. Opening of these gateways initiated oceanic circulation between the Arctic and the rest of the Atlantic, and is thus relevant to climatic studies. The event affected the Atlantic current pattern and triggered the development of contourite currents that eroded pre-existing shelf edges, as well as deposited significant drift deposits. In the more landward areas of the eastern Norwegian Sea, a major unconformity and prograding shelf sequences suggest uplift and erosion of the northern Scandinavian mainland during the Miocene.
On a more local scale, a large number of compressional features either formed or became reactivated within the NE Atlantic continental margins. These features are almost ubiquitously located within the deep Cretaceous-Cenozoic depocentres, and they lie along an arc centered on Iceland. The focus of the deformation in the thick Cretaceous-Cenozoic basins reflects the low strength of the crust due to relatively recent crustal thinning. The arc shape of deformation around Iceland we associate with a proposed major growth phase of the Iceland Insular Margin, which set up a radially oriented body force directed toward the surrounding margins. Breaching of the Greenland - Faroes Ridge at the Faroes Conduit was probably related to compressional buckling.
The area inboard of the now abandoned Aegir Ridge, the Møre Basin, notably lacks compressional structures. We associate this absence of deformation with shielding by the Aegir Ridge, which experienced waning seafloor spreading as the neighboring Kolbeinsey Ridge succeeded. We envision that the Aegir Ridge absorbed the body force from Iceland by slowing down to ultraslow spreading.
Also the southern mountainous part of the Norwegian mainland appears to have started rising in Middle Miocene time, as recorded by sediments that were shed westward into the North Sea and southward toward Denmark. While poorly dated, major shelf progradation on the NE Greenland margin probably also reflects uplift and erosion. These semi-regional uplifts are strong candidates for nucleation sites for ice caps during the Late Pliocene northern hemisphere climatic deterioration. Glacial erosion further eroded already uplifted areas, thereby enhancing the uplifts and generating the modern landscape.