Separation of rifting and lithospheric folding signatures in the NW-Alpine foreland

Research areas:
Year:
2007
Authors:
  • Olivier Bourgeois
  • M. Ford
  • M. Diraison
  • C. Le Carlier de Veslud
  • M. Gerbault
  • R. Pik
  • N. Ruby
  • S. Bonnet
Journal:
INTERNATIONAL JOURNAL OF EARTH SCIENCES
Volume:
96
Number:
6
Pages:
1003-1031
Month:
November
ISSN:
1437-3254
BibTex:
Abstract:
The development of the Alpine mountain belt has been governed by the
convergence of the African and European plates since the Late
Cretaceous. During the Cenozoic, this orogeny was accompanied with two
major kinds of intraplate deformation in the NW-European foreland: (1)
the European Cenozoic Rift System (ECRIS), a left-lateral transtensional
wrench zone striking NNE-SSW between the western Mediterranean Sea and
the Bohemian Massif; (2) long-wavelength lithospheric folds striking NE
and located between the Alpine front and the North Sea. The present-day
geometry of the European crust comprises the signatures of these two
events superimposed on all preceding ones. In order to better define the
processes and causes of each event, we identify and separate their
respective geometrical signatures on depth maps of the pre-Mesozoic
basement and of the Moho. We derive the respective timing of rifting and
folding from sedimentary accumulation curves computed for selected
locations of the Upper Rhine Graben. From this geometrical and
chronological separation, we infer that the ECRIS developed mostly from
37 to 17 Ma, in response to north-directed impingement of Adria into the
European plate. Lithospheric folds developed between 17 and 0 Ma, after
the azimuth of relative displacement between Adria and Europe turned
counter-clockwise to NW-SE. The geometry of these folds (wavelength =
270 km; amplitude = 1,500 m) is consistent with the geometry, as
predicted by analogue and numerical models, of buckle folds produced by
horizontal shortening of the whole lithosphere. The development of the
folds resulted in ca. 1,000 m of rock uplift along the hinge lines of
the anticlines (Burgundy-Swabian Jura and Normandy-Vogelsberg) and ca.
500 m of rock subsidence along the hinge line of the intervening
syncline (Sologne-Franconian Basin). The grabens of the ECRIS were
tilted by the development of the folds, and their rift-related
sedimentary infill was reduced on anticlines, while sedimentary
accumulation was enhanced in synclines. We interpret the occurrence of
Miocene volcanic activity and of topographic highs, and the basement and
Moho configurations in the Vosges-Black Forest area and in the Rhenish
Massif as interference patterns between linear lithospheric anticlines
and linear grabens, rather than as signatures of asthenospheric plumes.