Terminology of anticlines and different folds Anticline

diagram showing constituent parts of anticline

an antiform can used describe fold convex up. relative ages of rock strata distinguish anticlines antiforms. hinge of anticline refers location curvature greatest, called crest. hinge highest point on stratum along top of fold. culmination refers highest point along geologic structure. limbs sides of fold display less curvature. inflection point area on limbs curvature changes direction.

the axial surface imaginary plane connecting hinge of each layer of rock stratum through cross section of anticline. if axial surface vertical , angles on each side of fold equivalent, anticline symmetrical. if axial plane tilted or offset, anticline asymmetrical. anticline cylindrical has well-defined axial surface, whereas non-cylindrical anticlines complex have single axial plane.

an overturned anticline asymmetrical anticline limb has been tilted beyond perpendicular, beds in limb have flipped on , may dip in same direction on both sides of axial plane. if angle between limbs large (70–120 degrees), fold open fold, if angle between limbs small (30 degrees or less), fold tight fold. if anticline plunges (i.e., anticline crest inclined earth s surface), form vs on geologic map view point in direction of plunge. plunging anticline has hinge not parallel earth s surface. anticlines , synclines have degree of plunge. periclinal folds type of anticlines have well-defined, curved hinge line , doubly plunging , elongate domes.

model of anticline. oldest beds in center , youngest on outside. axial plane intersects center angle of bend. hinge line follows line of greatest bend, axial plane intersects outside of fold.

folds in limbs dip toward hinge , display more u-like shape called synclines. flank sides of anticlines , display opposite characteristics. syncline s oldest rock strata in outer limbs; rocks become progressively younger toward hinge. monocline bend in strata resulting in local steepening in 1 direction of dip. monoclines have shape of carpet draped on stairstep.

an anticline has been more eroded in center called breached or scalped anticline. breached anticlines can become incised stream erosion, forming anticlinal valley.

a structure plunges in directions form circular or elongate structure dome. domes may created via diapirism underlying magmatic intrusions or upwardly mobile, mechanically ductile material such rock salt (salt dome) , shale (shale diapir) cause deformations , uplift in surface rock. richat structure of sahara considered dome has been laid bare erosion.

an anticline plunges @ both ends termed doubly plunging anticline, , may formed multiple deformations, or superposition of 2 sets of folds. may related geometry of underlying detachment fault , varying amount of displacement along surface of detachment fault.

an anticlinorium large anticline in series of minor anticlinal folds superimposed. examples include late jurassic cretaceous purcell anticlinorium in british columbia , blue ridge anticlinorium of northern virginia , maryland in appalachians, or nittany valley in central pennsylvania.