Economic Consequences of Geologic Structures Tracing Coal Seams, Aquifers, etc. Folds Small Structures Anticline Syncline Monocline Homocline Large Structures Dome Basin Arch, Swell, Upwarp Foliation Foliation is a sheetlike structure that forms when rocks are deformed. As the figures show, it forms in a variety of ways, but in every case, the foliation is at right angles to the direction of greatest compression. Solutions often remove large amounts of material from rocks as they are being deformed. The solutions move in the direction of least resistance.
Elongate crystals grow in the direction of least resistance.
This is one possible way banding in gneiss forms. As the shear deformation becomes greater, the foliation becomes stronger and more closely aligned with the fault plane. Banding in Gneiss a. Often the banding in gneiss is a relic of original bedding, especially if the original rocks had alternating beds of dissimilar composition. As ferromagnesian minerals form, they accumulate iron and magnesium from their surroundings, which become depleted.