Structural styles - northern Subalpine chains

The northern Subalpine chains were over-ridden by a thrust sheet made up of rocks from the Internal Zones of the Alps.  This sheet is now preserved as a few so-called Prealpine klippen (klippe is the singular).  This sheet buried its footwall by several kilometres and provided a blanket beneath which the footwall warmed up to over 200 degrees C.  Thrust structures that formed beneath this blanket in the Mesozoic sediments formed a broad type of duplex.  However, the structural style here includes more than just simple thrust structures.  Different levels in the stratigraphy deformed in different ways.  Use the stratigraphic column to see how.  The field photographs come from the Arve Valley, north of the Bornes-Aravis area.

Thrust repetition of the Urgonian limestone unit, seen in the Arve valley near the town of Cluses.  In this view we are looking east, back down the thrusting direction. back to top of page

The Arpennaz Fold.  This classic structure is an asymmetric fold pair developed in Tithonian limestones seen on the north side of the Arve valley at Sallanches (west to the left).  The top of the hillside contains the prominent bank of Urgonian limestone, with the intervening lower Cretaceous rocks less well exposed.   You can use this view to establish vergence and facing of the fold pair.  The hillside is about 2000m high. back to top of page