Processes
Folding
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The permanent bending of originally planar surfaces such as sedimentary strata into curved forms, from microscopic crinkles to mountain-sized folds, singly or in periodic fold trains. Folds form under varied conditions of stress, pore pressure and temperature, most commonly by shortening of existing layers, and a set of folds distributed on a regional scale constitutes a fold belt, a common feature of orogenic zones.
Facts
TimescaleThousands to millions of years, developing over the same timescales as the mountain-building episodes that typically drive it. 1 Driving ForceWhen a sequence of layered rock is shortened parallel to its own layering, that deformation can be accommodated by folding, among other mechanisms. 1 Resulting FeatureFolding produces anticlines, arch-shaped folds whose strata dip away from the axis and whose oldest layers sit at the center. 1 SignificanceFolded rock can trap hydrocarbons: a porous sandstone layer capped by low-permeability shale and folded into an anticline can form an oil or gas trap. 1 Cross-Tradition Connections
Associated With
Folds may form from displacement on a non-planar fault or at the tip of a propagating fault.
A fold belt is a common feature of orogenic zones.
The principle is important to the analysis of folded and tilted strata.
Folding is one of the primary deformation structures structural geology reconstructs the history of.
In Discipline
A subject of structural geology.
Sources
1. Fold, Geology (Wikipedia)
Wikimedia FoundationLead sectionQuote, Lead section
a fold is a stack of originally planar surfaces, such as sedimentary strata, that are bent or curved
1. Fold, Geology (Wikipedia)
Wikimedia FoundationCauses of foldingQuote, Causes of folding
When a sequence of layered rocks is shortened parallel to its layering, this deformation may be accommodated in a number of ways, homogeneous shortening, reverse faulting or folding.
1. Fold, Geology (Wikipedia)
Wikimedia FoundationTypes of fold (anticline)Quote, Types of fold (anticline)
Anticline: linear, strata normally dip away from the axial center, oldest strata in center irrespective of orientation.
1. Fold, Geology (Wikipedia)
Wikimedia FoundationOil industryQuote, Oil industry
Anticlinal traps are formed by folding of rock. For example, if a porous sandstone unit covered with low permeability shale is folded into an anticline, it may form a hydrocarbons trap.
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