Petrological, structural and seismic signature of shallow crustal chiseling and crustal splitting: role of paleorift heredity
Abstract
Since the concept of crustal flakes was introduced in geology in early seventies the tectonic or lithospheric wedging was recognized in several seismic lines through Alps, Pyrenees, Rocky Mountains and Appalachians. The common factor of all these domains is an existence of rifted lithosphere of different thermal age and their complex seismic pattern is interpreted as a result of single or even double lithospheric wedging. We present 1D and 2D numerical simulations to evaluate the role of cooling time of rifted domain and lithological make-up on the localisation of major detachment zones controlling the depth and thickness of crustal or lithospheric chisels. We show three key configurations of pre-rift and post rift conditions represented by standard crust and hot geotherm (rifted) versus thin crust and mean geotherm (stable), standard crust and mean geotherm (rifted) versus thin crust and mean geotherm (stable), thin crust and hot geotherm (rifted) versus thin crust mean geotherm (stable). We present two geological sections and seismic lines of European Variscides where geochronological, petrological and reliable structural data are available to discuss the geometry of modelled crustal chisels. The role of tectonic heredity, time of cooling and differential strength of cooled rifted domain versus adjacent continent is discussed in terms of exhumation of deep seated rocks and development of ductile structures along strong chisel and adjacent weak zone. Continuous structural and metamorphic history in vertical and lateral directions is explained using the role of transient plastic instabilities during chiselling.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....8392S