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If the angle between the limbs is large (70–120 degrees), then the fold is an "open" fold, but if the angle between the limbs is small (30 degrees or less), then the fold is a "tight" fold. [4] If an anticline plunges (i.e., the anticline crest is inclined to the Earth's surface), it will form V s on a geologic map view that point in the ...
When the limbs of a fold converge upward, the fold is referred to as an antiform. Conversely, when the limbs of a fold converge downward, the fold is known as a synform. Not to be confused with these terms (antiform and synform), the terms anticline and syncline are used in the description of the stratigraphic significance of the fold.
See the main article on folds for a fuller treatment of fold types and nomenclature but in brief, an anticline is an arch-like fold whereas a syncline is its converse; a downfold. Antiforms , anticlinoria , synforms and synclinoria are variations on these.
For example, if a porous sandstone unit covered with low permeability shale is folded into an anticline, it may form a hydrocarbons trap, oil accumulating in the crest of the fold. Most anticlinal traps are produced as a result of sideways pressure, folding the layers of rock, but can also occur from sediments being compacted.
Diagram of the evolution of a fault-bend fold or 'ramp anticline' above a thrust ramp, the ramp links decollements at the top of the green and yellow layers Diagram of the evolution of a fault propagation fold Development of thrust duplex by progressive failure of ramp footwall Antiformal stack of thrust imbricates proved by drilling, Brooks Range Foothills, Alaska
An example cross section of an anticline with a dike cutting through, with the map of its surface expression showing strike and dip information. Cross sections are made by interpreting and extrapolating a broad range of information about a region's geological characteristics. This can include data from the surface, subsurface, and existing ...
In response to compressional stress, geological beds fold in order to minimize dissipation of energy. Given an unconstrained bed, folding does so by correspondingly minimizing bending and thus develops a sinusoidal geometry. In a stratigraphic sequence, beds are geometrically and physically constrained by their neighbours.
Within regions that have experienced tectonic deformation, systematic joints are typically associated with either layered or bedded strata that have been folded into anticlines and synclines. Such joints can be classified according to their orientation in respect to the axial planes of the folds as they often commonly form in a predictable ...