Physics
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufm.t21c..01a&link_type=abstract
American Geophysical Union, Fall Meeting 2007, abstract #T21C-01
Physics
1025 Composition Of The Mantle, 1236 Rheology Of The Lithosphere And Mantle (7218, 8160), 7218 Lithosphere (1236), 8103 Continental Cratons
Scientific paper
While most of the East European Craton (EEC) lacks surface relief, the amplitude of topography at the top of the basement exceeds 20 km, variations in the thickness of the crystalline crust reach 50 km, and variations in the lithosphere thickness exceed 200 km. This study (Global Planet. Change, 2007, 58, 411-434) examines the relative contributions of the crust, the subcrustal lithosphere, and the dynamic support of the sublithospheric mantle to maintain surface topography, using regional seismic data on the structure of the crust and the sedimentary cover, and thermal and large-scale P- and S-wave seismic tomography data on the structure of the lithospheric mantle. The isostatic contribution of the crust to the surface topography of the EEC is found to be almost independent of age (ca. 4.5 km) due to an interplay of age- dependent crustal and sedimentary thicknesses and lithospheric temperatures. On the contrary, the contribution of the subcrustal lithosphere to the surface topography strongly depends on the age, being slightly positive (+0.3+0.7 km) for the regions older than 1.6 Ga and negative (-0.5-1 km) for younger structures. This leads to age- dependent variations in the residual topography, i.e. the topography which cannot be explained by the assumed thermal and density structure of the lithosphere, and which can (at least partly) originate from the dynamic component caused by the mantle flow. Positive dynamic topography at the cratonic margins, which exceeds +2 km in the Norwegian Caledonides and in the Urals, clearly links their on-going uplift with deep mantle processes. Negative residual topography beneath the Archean- Paleoproterozoic cratons (-1-2 km) indicates either a smaller density deficit (ca 0.9 per cent) in their subcrustal lithosphere than predicted by mantle-derived xenoliths or the presence of a strong convective downwelling in the mantle. Such mantle downflows can effectively divert heat from the lithospheric base, leading to a long-term survival of the Archean Paleoproterozoic lithosphere.
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