In structural geology, an anticline is a fold that is convex up and has its oldest beds at its core. Structural geology is the study of the three dimensional distribution of rock bodies and their planar or folded surfaces and their internal fabrics See also Folding The term fold is used in Geology when one or a stack of originally flat and planar surfaces such as Sedimentary In Euclidean space, an object is convex if for every pair of points within the object every point on the Straight line segment that joins them is also within the In Geology and related fields a stratum (plural strata) is a layer of rock or Soil with internally consistent characteristics that distinguishes The term is not to be confused with antiform, which is a purely descriptive term for any fold that is convex up. Therefore if age relationships (i. e. younging direction) between various strata are unknown, the term antiform must be used.
On a geologic map, anticlines are usually recognized by a sequence of rock layers that are progressively older toward the center of the fold because the uplifted core of the fold is preferentially eroded to a deeper stratigraphic level relative to the topographically lower flanks. In Geology, rock is a naturally occurring aggregate of Minerals and/or Mineraloids The Earth's outer solid layer the ‘ Lithosphere In Geology and related fields a stratum (plural strata) is a layer of rock or Soil with internally consistent characteristics that distinguishes The strata dip away from the center, or crest, of the fold. Strike and dip refer to the orientation or attitude of a Geologic feature
If an anticline plunges (i. e. , is inclined to the earth's surface), the surface strata will form Vs that point in the direction of plunge. Anticlines are typically flanked by synclines although faulting can complicate and obscure the relationship between the two. In Structural geology, a syncline is a downward-curving fold, with layers that dip toward the center of the structure In Geology a fault, or fault line, is a planar rock fracture which shows evidence of relative movement Folds typically form during crustal deformation as the result of compression that accompanies orogenic mountain building. Orogeny (Greek for "mountain generating" is the process of natural Mountain building and may be studied as a tectonic structural event as a geographical event and
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Anticline terminology
Any fold whose form is convex upward is an antiform. Antiforms containing progressively younger rocks from their core outwards are anticlines.
An anticline or antiform has a crest, which is the highest point on a given stratum along the top of the fold. A hinge in an anticline is the locus of maximum curvature or bending in a given stratum in the fold. An axis is an imaginary line connecting the hinges in the different strata in a two-dimensional cross-section through the anticline. Connecting the hinges or points of maximum curvature in the different layers in three dimensions produces an axial plane or axial surface. In a symmetrical anticline, a surface trace of the axial plane coincides with the crest. With an asymmetrical anticline, the surface trace of the axial plane or axis will be offset from the crest toward the steeper flank of the fold. An overturned anticline is an asymmetrical anticline with a flank or limb that has been tilted beyond perpendicular so that the beds in that limb are upside-down.
A structure that plunges in all directions to form a circular or elongate structure is a dome. In Geology, a dome is a deformational feature consisting of symmetrically-dipping Anticlines their general outline on a geologic Map is circular or oval Domes are generally formed from one main deformation event, or via diapirism from underlying magmatic intrusions or movement of upwardly mobile, mechanically ductile, material such as rock salt (salt dome) and shale (shale diapir). A diapir (ˈdaɪəpɪər) ( French, from Greek diapeirein, to pierce through is an Intrusion caused by Buoyancy and Pressure
An anticline which plunges at both ends is termed a doubly-plunging anticline, and may be formed from multiple deformations, or superposition of two sets of folds, or be related to the geometry of the underlying detachment fault and the varying amount of displacement along the surface of that detachment fault. The highest point on a doubly-plunging anticline (or any geologic structure for that matter) is called the "culmination. "
An elongate dome which developed as the sediments were being deposited is referred to as a pericline.
An anticlinorium is a series of parallel anticlinal folds on a regional-scale anticline. Example include the Late Jurassic to Early Cretaceous Purcell Anticlinorium in British Columbia[1] and the Blue Ridge anticlinorium of northern Virginia in the Appalachians [2]. The Jurassic is a geologic period and system that extends from about Ma (million years ago to Ma that is from the end of the Triassic to the beginning The Cretaceous (kriːˈteɪʃəs, usually abbreviated 'K' for its German translation "Kreide" is a geologic period and system, reaching from the end of British Columbia (ˌbrɪtɨʃ kəˈlʌmbiə ( BC) ( (la Colombie-Britannique C The Commonwealth of Virginia ( is an American state The Appalachian Mountains ( often called the Appalachians, are a vast system of mountains in eastern North America.
Economic significance
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Doubly-plunging or faulted anticlines, culminations, and structural domes are favored locations for oil and natural gas drilling; the low density of petroleum causes it to buoyantly migrate upward to the highest parts of the fold, until stopped by a low-permeability barrier such as an impermeable stratum or fault zone. An oil is a substance that is in a viscous Liquid state ( "oily") at ambient temperatures or slightly warmer and is Natural gas is a Gaseous Fossil fuel consisting primarily of Methane but including significant quantities of Ethane, Propane, Examples of low-permeability seals that contain the hydrocarbons, oil and gas, in the ground include shale, limestone, sandstone, and even salt domes. The actual type of stratum does not matter as long as it has low-permeability.
Periclines are important focal points for pooling of hot, metal-laden formational brines, which can form manto ore deposits, Irish-type lead-zinc deposits and uranium deposits, amongst others. Brine (lat saltus) is Water saturated or nearly saturated with Salt (NaCl Manto orebodies are stratabound irregular to rod shaped Ore occurrences usually horizontal or near horizontal in attitude
Culminations in folded strata which are cut by shears and faults are favoured loci for deposition of saddle-reef style lode gold deposits. Study of geological shear is related to the study of Structural geology, Rock microstructure or rock texture and fault mechanics.
See also
- Homocline
- Monocline
- Syncline
- Weald-Artois Anticline - linked Britain to continental Europe until 225,000 years ago
- Makhtesh
References
- Bates, Robert L. In Structural geology, a uniclinal structure, homoclinal structure, unicline or homocline (from old homo = same cline monocline is a step-like fold consisting of a zone of steeper dip within an otherwise horizontal or gently-dipping sequence In Structural geology, a syncline is a downward-curving fold, with layers that dip toward the center of the structure The Weald-Artois Anticline is a geological structure running between the regions of the Weald in southern England and Artois in north eastern France See also Kingdom of Great Britain Great Britain (Breatainn Mhòr Prydain Fawr Breten Veur Graet Breetain is the larger of the two main islands A makhtesh (מכתש plural מכתשים - "makhteshim" is a geological landform regarded to be unique to the Negev desert of Israel and the , and Julia A. Jackson, editors. Dictionary of Geological Terms: Prepared under the direction of the American Geological Institute, Anchor Press/Doubleday, Garden City, New York.
- Davis, George H. , Reynolds, Stephen J. , 1996. Structural Geology of Rocks and Regions: John Wiley & Sons, Inc. , New York. ISBN 0-471-52621-5
- Monroe, James S. , and Reed Wicander. The Changing Earth: Exploring Geology and Evolution. 2nd ed. Belmont: Wadsworth Publishing Company, 1997. ISBN 0-314-09577-2
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