The "passive" margins of the North Atlantic - revisiting the geological evidence of uplift and subsidence

Category Tectonic & Seismotectonic
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Anell, Ingrid; Thybo, Hans; Irina, Artemieva
Holding Date 11 October 2008

Evidence has been accumulating during recent years that the passive margins around the North Atlantic are not quite as "passive" as might be expected. There is substantial evidence indicating periods of onshore uplift and abrupt increases in subsidence of offshore basins. The evidence is, however, controversial. All methods have problems distinguishing tectonically induced uplift from increased erosion caused by climatic changes, eustatic sea-level changes and isostatic compensation. Further, localised uplift generated by inversion and compression tectonics impedes identification of regional uplift events.
Uplift and subsidence around the North Atlantic margins is an area of extensive debate. The aim of this study is to provide an overview of past studies.
Most authors agree that substantial uplift occurred along the margins bordering the break-up between Norway and Greenland in the Palaeocene-early Eocene. This uplift propagated northward with the opening of the spreading axis. Uplift was probably related to emplacement of the North Atlantic Igneous Province (NAIP), the Iceland thermal anomaly and rift-related flank uplift. An earlier episode of ca. middle Palaeocene uplift and over-deepening of basins occurred in the North Sea and around the British Isles. This possibly occurred in response to both the Laramide phase of the Alpine Orogeny and early NAIP magmatism. In the Eocene a seemingly radial shaped phase of rapid subsidence centred around Iceland occurred. The radial shape indicates a possible relation to a decrease in intensity of the Iceland thermal anomaly. The late Eocene - Oligocene sees phases of uplift on both eastern and western margins of Greenland. This may be related to cessation of sea-floor spreading in the Labrador Sea on the western margin, and intrusive volcanism and/or the ridge-jump from the Aegir to Kolbeinsey ridge affecting the eastern margin.
In the Oligocene uplift occurred in southern Fennoscandia, around the North Sea and the British Isles. These areas are located within the region affected by inversion and compressional doming, suggesting a possible causal relation. The exact timing is unclear and uplift may have occurred in two phases; in the late Eocene-early Oligocene, and late Oligocene. A similar scenario occurs around the mid(?) Miocene. Late Miocene and Plio-Pleistocene uplift is proposed for most marginal land-areas and it appears that glaciation had a strong impact. However, to what extent factors other affected uplift is inconclusive. Simultaneous offshore subsidence is also proposed at this time.