Recent deep-crustal seismic reflection profiling across the central
Alps of eastern and southern Switzerland has provided a detailed
image of this continental collision zone. As part of the Swiss National
Science project NFP 20, a series of reflection profiles was recorded
during two phases along N-S transects crossing the Alpine edifice.
The eastern and southern profiles coincide with the Alpine segment
of the European Geotraverse (EGT) and in part with the earlier Swiss
Geotraverse. These data together with other geophysical and extensive
geologic information form a unique and comprehensive volume of crustal
information for this region of the Alps. On a larger scale, the new
reflection data also add to a growing set of profiles crossing the
Alpine fold belt which includes an additional traverse carried out
by NFP 20 across the western Swiss Alps and the ECORS-CROP profile
across the western Alps. The initial results of the reflection data
across the central Alps outline a crustal framework involving northward
indentation of the Adriatic hinterland into the subducting European
foreland. This occurs beneath the collapsed oceanic basins of the
Penninic allochthon which is defined by its highly reflective crystalline
nappes. The present crustal thickness within the Alpine collision
zone has doubled to about 60 km by both vertical and horizontal displacements
along an inferred complex detachment system controlled by the Adriatic
wedge. The south-plunging European foreland implies that portions
of the thickened crust have been subducted into the upper mantle.
This general framework of flake tectonics is laterally consistent
with the ECORS-CROP results, from the western Alps. However, the
western Alps show a higher degree of crustal imbrication which may
be related to the presence of the rigid Ivrea body and an overall
greater amount of crustal shortening compared to the central Alps.