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Slope of Mount Pilatus

The steep sides of Mount Pilatus, south of Lucerne, are seen on the left. The rocks are mostly Cretaceous sediments.

Folded Sediments of Mount Pilatus

View to the west (left) near the top of Mount Pilatus, south of Lucerne. Note the very contorted layers. The mountain was overthrust about 50 km from the south (left of picture).

nappe folding Overthrust tectonics

Monocline

A monocline is a fold with a subhorizontal flank passing into a high angle flank. It is usually related to the activity of a tectonic lineament, like a thrust.

Structural tectonics folding

SEDIMENTARY - CHEMICAL: Pennsylvanian Eagle Valley evaporites, Rt.82 south of Glenwood Springs --- Gypsum is assumed to have formed in a hot, arid climate by evaporation of sea water in a closed basin causing the precipitation of calcium sulfate. After burial, this soft rock easily flows forming the chevron fold seen in this picture.

evaporites folding

Recumbent anticline

Anticlinal folding in Pennsylvanian strata of the Belden Fm. (Sweetwater Creek, near Dotsero, CO). Monoclinal to recumbent folds (similar to this one) can be caused by displacement connected with the termination of a thrust fault buried at depth. Some have interpreted this particular fold in this way, linking it with thrust activity during the Laramide orogeny. Note that the lithology of the Belden Fm., which consists of bedded shales, limestone, and evaporites, favors ductile deformation. Layers that tend to resist plastic deformation under stress are termed "competent," and a contrast between competent (e.g., sandstone, chert) and less competent (e.g., shale, gypsum) beds can produce spectacular folding.

folding anticline deformation Pennsylvanian thrust