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In structural geology, an anticline is a type of fold that is an arch-like shape and has its oldest beds at its core, whereas a syncline is the inverse of an anticline. A typical anticline is convex up in which the hinge or crest is the location where the curvature is greatest, and the limbs are the sides of the fold that dip away from the hinge.
A river anticline is a geologic structure that is formed by the focused uplift of rock caused by high erosion rates from large rivers relative to the surrounding areas. [1] An anticline is a fold that is concave down, whose limbs are dipping away from its axis, and whose oldest units are in the middle of the fold. [ 2 ]
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.
The fold is around 35 kilometres (22 mi) long, running from north of Michelmersh near the River Test to East Meon in the valley of the River Meon. In the Winchester area the core of the anticline has been eroded to expose the older Cenomanian Zig Zag Chalk formation in Chilcomb and Bar End (the 'Lower chalk').
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. A monocline (or, rarely, a monoform) is a
The Weald–Artois Anticline, or Wealden Anticline, is a large anticline, a geological structure running between the regions of the Weald in southern England and Artois in northern France. The fold formed during the Alpine orogeny, from the late Oligocene to middle Miocene as an uplifted form of the Weald basin through inversion of the basin.
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.
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