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A synclinorium (plural synclinoriums or synclinoria) is a large syncline with superimposed smaller folds. [1] Synclines are typically a downward fold (synform), termed a synformal syncline (i.e. a trough), but synclines that point upwards can be found when strata have been overturned and folded (an antiformal syncline).
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.
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.
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.
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.
Fig. 8: An animation on the evolution of a fault-bend fold, Note that 2 anticlines and synclines are formed at the final stage of the progression. A detachment fold can evolve into a forced fold when shortening stress exceeds the maximum strength of rock , and as a result the decollement may propagate upwards towards the anticlinal core and ...
The formation of an asymmetric anticline-syncline fold pair accommodates the continuing displacement. As displacement continues, the thrust tip starts to propagate along the axis of the syncline. Such structures are also known as tip-line folds. Eventually, the propagating thrust tip may reach another effective decollement layer, and 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.