Folds, cleavage, and boudinage

Upright chevron folds in dm-bedded Late Cretaceous calciturbidites of the Slovenian Basin, west of Most na Soče, Slovenia.
Upright chevron folds in dm-bedded Late Cretaceous calciturbidites of the Slovenian Basin, west of Most na Soče, Slovenia.
Image: Kamil Ustaszewski
Anticline in Lower Carboniferous slates with well-developed axial plane cleavage. Saxothuringian domain, at Ziegenrück (Thuringia, central Germany). Three geologist's kids, sitting in the anticline's hinge, serve as a scale.
Anticline in Lower Carboniferous slates with well-developed axial plane cleavage. Saxothuringian domain, at Ziegenrück (Thuringia, central Germany). Three geologist's kids, sitting in the anticline's hinge, serve as a scale.
Image: Kamil Ustaszewski
Axial plane cleavage in folded pelagic limestones. Kirit river at Prekali, northern Albania.
Axial plane cleavage in folded pelagic limestones. Kirit river at Prekali, northern Albania.
Image: Kamil Ustaszewski
Folded pelagic limestones with incipient fracture cleavage and a ptygmatically folded chert layer (dark grey) in the antiform's core. See next picture in the gallery for a more detailed view of the fold core. Kirit river at Prekali, northern Albania.
Folded pelagic limestones with incipient fracture cleavage and a ptygmatically folded chert layer (dark grey) in the antiform's core. See next picture in the gallery for a more detailed view of the fold core. Kirit river at Prekali, northern Albania.
Image: Kamil Ustaszewski
Crenulation cleavage affecting a succession of metasandstones (light grey) and darker coloured metapelitic schists. Taroko gorge, eastern Taiwan.
Crenulation cleavage affecting a succession of metasandstones (light grey) and darker coloured metapelitic schists. Taroko gorge, eastern Taiwan.
Image: Kamil Ustaszewski
South-vergent folds in paragneiss of the Sesia Zone above Pieve Vergonte (Valle d’Ossola, Piemonte, Italy). The folds were formed synkinematically with mylonitisation along the Insubric Fault: Towards south, the axial-plane cleavage of such folds becomes increasingly intense and grades into proper Insubric mylonites. The Insubric mylonites straddle the boundary between Southern and Penninic Alps (see Pleuger et al., 2008).
South-vergent folds in paragneiss of the Sesia Zone above Pieve Vergonte (Valle d’Ossola, Piemonte, Italy). The folds were formed synkinematically with mylonitisation along the Insubric Fault: Towards south, the axial-plane cleavage of such folds becomes increasingly intense and grades into proper Insubric mylonites. The Insubric mylonites straddle the boundary between Southern and Penninic Alps (see Pleuger et al., 2008).
Image: Jan Pleuger
Non-tectonic, 'lasagne-style' folds formed at laboratory conditions in Italian pasta. The folds formed due to volume increase of a few percent during heating at 180°C for 45 min, while the bounding box, made of low-thermal expansion borosilicate glass, has remained undeformed. Vertical scale is approximately 5 cm.
Non-tectonic, 'lasagne-style' folds formed at laboratory conditions in Italian pasta. The folds formed due to volume increase of a few percent during heating at 180°C for 45 min, while the bounding box, made of low-thermal expansion borosilicate glass, has remained undeformed. Vertical scale is approximately 5 cm.
Image: Kamil Ustaszewski
Two fold generations affecting paragneiss of the Sesia zone (near Vogogna, Val d’Ossola, Piemonte, Italy). The axial plane foliation of the second fold generation is nearly vertical and corresponds to the mylonitic foliation along the Insubric fault which offset the Penninic Alps with respect to the Southern Alps by a few tens of kilometres.
Two fold generations affecting paragneiss of the Sesia zone (near Vogogna, Val d’Ossola, Piemonte, Italy). The axial plane foliation of the second fold generation is nearly vertical and corresponds to the mylonitic foliation along the Insubric fault which offset the Penninic Alps with respect to the Southern Alps by a few tens of kilometres.
Image: Jan Pleuger
Refolded fold in paragneiss of the Sesia zone (near Pieve Vergonte, Val d‘Ossola, Piemonte, Italy). The nearly vertical axial plane of the younger fold corresponds to the mylonitic foliation along the Insubric fault which offset the Penninic Alps with respect to the Southern Alps by a few tens of kilometres (see Pleuger et al., 2008).
Refolded fold in paragneiss of the Sesia zone (near Pieve Vergonte, Val d‘Ossola, Piemonte, Italy). The nearly vertical axial plane of the younger fold corresponds to the mylonitic foliation along the Insubric fault which offset the Penninic Alps with respect to the Southern Alps by a few tens of kilometres (see Pleuger et al., 2008).
Image: Jan Pleuger