Open Session - SWISS GEOSCIENCE MEETINGs

Schenk, V., Cacoń, S., Schenková, Z., Kontny, B., Bosy, J. & Kottnauer, P. 2002: The GPS geodynamic network East Sudeten. Five
annual campaigns (1997-2001), data processing and results. Acta Montana A, 20(124), 13-23.
Figure 1. Tectonic situation of northern Silesia (SMF – Sudetic Marginal Fault, 1 - Žulová granite pluton, 2 - Limestones of the Branná
group, 3 - Bělský fault, 4 - Klepáčovský fault, 5 – Ramzová overthrust, 6 – Nýznerov fault zone).
1.
Structural evolution of the Monte Rosa and Adula nappes and the
formation of the Lepontine dome
Pleuger Jan*, Nagel Thorsten**, Froitzheim Nikolaus**
*Geologisches Institut, ETH Zürich, Universitätsstraße 6, CH-8092 Zürich
**Steinmann-Institut, Bereich endogene Prozesse, Nußallee 8, D-53115 Bonn
The structural evolutions of the Monte Rosa and Adula nappes and their surrounding units are compared in order to develop
a possible kinematic scenario for the formation of the Lepontine dome structure in the Swiss Central Alps. Towards west and
east, nappe contacts and structures dip moderately away from the core of the Lepontine dome while they are bent into steeply
dipping to overturned positions in the Southern Steep Belt north of the Periadriatic fault. The comparison of the Monte
Rosa and Adula nappes allows to discuss the formation of the Lepontine dome structure since the Monte Rosa nappe extends
into the Southern Steep Belt from the western flank of the Lepontine dome while the Adula nappe is situated in the eastern
flank of that structure.
The Monte Rosa nappe was subject to five successive deformation phases postdating the eclogite-facies pressure peak at c. 42
Ma: (1) northwest-vergent shearing with only minor and small-scale folding (Mattmark phase, D 1 ); (2) southwest-vergent
shearing with formation of large-scale tight to isoclinal folds (Malfatta phase, D 2 ); (3) southeast-vergent shearing with formation
of large-scale open to tight southwest-vergent folds (Mischabel phase, D 3 ); (4) formation of the upright Vanzone fold and
continuing southeast-vergent shearing (Vanzone phase, D 4 ); mostly dextral but also some sinistral shearing confined to the
southern limb of the Vanzone antiform (Olino phase, D 5 ).
Similar as in the Monte Rosa nappe, the eclogite-facies pressure peak in the Adula nappe was reached c. 40 Ma ago. It was
postdated by northwest-vergent shearing (Zapport phase, D 1 ) which in turn was followed by eastnortheast-westsouthwestoriented
shearing of the Leis phase (D 2 ). Though the significance of D2 Malfatta- and Leis-phase movements for the exhuma-
Symposium 1: Structural Geology, Tectonics and Geodynamics
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