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| Titel |
Cenozoic Transient Convective Uplift of the North Atlantic European Margin |
| VerfasserIn |
Ross Hartley, Gareth Roberts, Nicky White |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250074772
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| Zusammenfassung |
| Given that the Rayleigh number of the convecting mantle is 106 to 108, instabilities should
occur over a range of length and time scales (100–1000 km, 0.1–100 Myr). Tomographic
measurements of seismic wave velocities in the mantle, long wavelength gravity
observations, surface elevation and the geochemical signature of volcanism can be used to
reveal the existence of convective upwellings. Beneath the North Atlantic Ocean, there is
evidence to suggest that the region has been affected, for the last 60 Myr, by the presence of
an upwelling plume, which is currently centred beneath Iceland. Short-lived (i.e. < 1 Myr)
variations in temperature of 10–100 °C are inferred from the pattern of bathymetry and short
wavelength gravity south of Iceland, where a series of V-shaped ridges occur. These
temperature variations should give rise to an associated variation in dynamic support of the
overlying plate and result in vertical motion of the surface over timescales of < 1
Myr.
Interpretation of 3D seismic reflection data from the Faroe Shetland Basin, a Cenozoic
sedimentary basin located 200 km north of the British Isles, has revealed a spectacular
terrestrial unconformity dated at ~55 Ma, today buried under up to 2 km of sediment in water
depths of up to 1km. The existence of this unconformity indicates that the basin underwent up
to 1 km of uplift in 1 Myr followed by subsidence of 1 km in 1 Myr. There is also
evidence for magmatic and volcanic activity in the basin at these times. These vertical
motions can be attributed to the passage of a thermal plume transient beneath the
basin. Inversion of longitudinal river profiles which drained this sub-aerial landscape
allows a detailed history of uplift to be calculated. This uplift history reveals that
the basin was uplifted in three stages with maximum uplift rates of 3 km Myr-1.
Therefore, the plume transient must have had a complicated thermal and/or chemical
structure. Evidence for heterogeneity in the mantle over these short scales has not
been observed in the sedimentary record before, however, it is supported by the
composite nature of the V-shaped ridges. The presence of ~58 Ma, ~55 Ma and
~50 Ma unconformities within the Faroe Shetland Basin suggests that this basin
was affected by the passage of multiple plume transients during Paleogene times. |
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