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Conference Papers Year : 2008

Horizontal compression and stress concentration at passive margins: causes, consequences, and episodicity

P.R. Cobbold
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Late uplift and exhumation at regional scale are common to many a passive margin. By consensus, amongst the likely mechanisms are thermal relaxation after rifting, deep-seated mantle flow, offshore sedimentation, onshore exhumation, and tectonic stress. Probably no one mechanism can account for all of the uplift and exhumation of a margin. Here I will make the case for horizontal compression, as an important mechanism in some instances. The World Stress Map project provides useful insights into current stress distributions. Horizontal compression dominates in many plates, including some (but not all) continental margins. Continental collision, ridge push, and slab pull can account for horizontal compression. However, radial patterns of trajectories provide evidence for stress concentrations. A well-known example is Central Asia, where the cause is indentation by a colliding India. In the northern hemisphere, there is good evidence that the Iceland plume, whatever its origin, is another source of stress concentration. The pattern is best seen on azimuthal projections, which centre on Iceland itself. It would appear to be responsible for thrust mechanisms of recent earthquakes in Scandinavia. In the geological record, there is also evidence for anomalies in seafloor spreading and basin inversion around Iceland, at least since the Neogene. Excess seafloor spreading appears to have transmitted, via reactivated fracture zones, to the continental margin of Norway. Thus the Iceland plume and the North Atlantic ridge, acting together, may have provided enough compression to account for basin inversion on North Atlantic margins. They may even account, at least in part, for Neogene to recent mountain building in adjacent onshore areas of Scandinavia, Scotland, Svalbard, Greenland, Baffin Island, Ellesmere Island and Labrador. More generally, for such a mechanism to be viable, a ridge-centred plume should close to a continental margin. I discuss the likelihood of such a mechanism having operated in the South Atlantic during the Late Cretaceous and Palaeogene, and having contributed to inversion in SE Brazil. Even more generally, uplift and exhumation on passive margins would seem to be episodic in nature. Some of the known episodes correlate with phases of mountain building and rapid plate convergence worldwide. This in itself is an argument for horizontal compression being a significant mechanism in the uplift and exhumation of some passive margins


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insu-00376344 , version 1 (17-04-2009)


  • HAL Id : insu-00376344 , version 1


P.R. Cobbold. Horizontal compression and stress concentration at passive margins: causes, consequences, and episodicity. International Geological Congress 33, Sep 2008, Oslo, Norway. ⟨insu-00376344⟩
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