Fold and thrust belt

A fold and thrust belt (FTB) is a series of mountainous foothills adjacent to an orogenic belt, which forms due to contractional tectonics. Fold and thrust belts commonly form in the forelands adjacent to major orogens as deformation propagates outwards. Fold and thrust belts usually comprise both folds and thrust faults, commonly interrelated. They are commonly also known as thrust-and-fold belts, or simply thrust-fold belts.

Modelling of a fold and thrust belt in a sand box

Geometry

Fold and thrust belts are formed of a series of sub-parallel thrust sheets, separated by major thrust faults. As the total shortening increases in a fold and thrust belt, the belt propagates into its foreland. New thrusts develop at the front of the belt, folding the older thrusts that have become inactive. This sequential propagation of thrusts into the foreland is the most common. Thrusts that form within the belt rather than at the thrust front are known as "out-of-sequence".

Map view

In map view, fold and thrust belts are generally sinuous rather than completely linear.[1] Where the thrust front bulges out in the direction of tectonic transport, a salient is formed. Between the bulges the areas are known as recesses, reentrants or sometimes embayments.

Thrust belts
Profile through the Pyrenees. In the south a fold and thrust belt exists as sediments are folded and stacked (thrust) on top of the other.
An example of thin-skinned thrusting in Montana. The white Madison Limestone is repeated, with one example in the foreground (that pinches out with distance) and another to the upper right corner and top of the picture.

Africa
Thrustbelt name Age Structural style
Atlas Mountains
Cape Fold Belt

Asia
Thrustbelt name Age Structural style
Aravalli Range Precambrian
Himalayas Upper Cretaceous
Zagros fold and thrust belt Young and active deforming belt

Australia
Thrustbelt name Age Structural style
Eastern Lachlan Orogen Middle Paleozoic North-south oriented structures

Europe
Thrustbelt name Age Structural style
Alps Cenozoic
Scandinavian Caledonides Ordovician - Devonian
Carpathians Mesozoic - Tertiary

North America
Thrustbelt name Age Structural style
Alaska Range Late Cretaceous - Cenozoic Thick-skin
Anadyr Highlands Late Paleocene - Eocene Unknown
Antler Thrustbelt Carboniferous Thin-skin
Appalachians Late Paleozoic Thin-skin
Arctic Cordillera Middle Devonian - Early Carboniferous Unknown
Brooks Range Jurassic - Early Cretaceous, Early Cenozoic Thin-skin
California Coast Ranges Late Miocene - Quaternary Transpressional
Chihuahua Belt Paleocene Unknown
Chugach Mountains Cenozoic Thin-skin
Eurekan Fold Belt Eocene - Oligocene Unknown
Innuitian Fold-Thrust Belt Late Cretaceous - Early Cenozoic Thin-skin
Kuskokwim Mountains Late Cretaceous - Eocene Unknown
Mackenzie Mountains Late Cretaceous - Middle Eocene Thin-skin
Maria Fold and Thrust Belt Cretaceous Thick-skin
North Greenland Fold Belt Middle Devonian - Early Carboniferous Unknown
Northern Ellesmere Fold Belt Middle Devonian - Early Carboniferous Thin-skin
Ogilvie Mountains Late Cretaceous - Eocene Thin-skin
Oregon Accretionary Prism Late Miocene - Quaternary Thin-skin
Ouachitas Late Carboniferous - Early Permian Thick- and thin-skin
Richardson Mountains Late Cretaceous - Middle Eocene Thin-skin
Rocky Mountains Paleocene to Middle Eocene Thick-skin
Selwyn Fold Belt, Yukon[2] Late Cretaceous Unknown
Sierra Madre Oriental Early Cenozoic Unknown
Sierra Madre Occidental Cretaceous - Eocene Unknown
South Canadian Rockies Late Jurassic - Eocene Thin-skin
Wyoming-Utah Thrustbelt (North Sevier) Late Jurassic - Eocene Thin-skin

Much of this table is adapted from Nemcok et al., 2005[3]

South America
Thrustbelt name Age Structural style
Magallanes (Fuegian) fold and thrust belt Late Cretaceous - Cenozoic Thin-skin
Malargüe fold and thrust belt
Marañón fold and thrust belt Cenozoic Thick-skin and thin-skin
Central Andean fold and thrust belt Mesozoic - Cenozoic Thin skin[4]

References
  1. Lickorish W.H.; Grasso M.; Butler R.W.H.; Argnani A.; Moniscalco R. (1999). "Structural styles and regional tectonic setting of the "Gela Nappe" and frontal part of the Maghrebian thrust belt in Sicily". Tectonics. 18 (4): 655–668. Bibcode:1999Tecto..18..655L. doi:10.1029/1999TC900013.
  2. Selwyn Basin Metallogeny Yukon Geological Survey Archived 2014-03-31 at the Wayback Machine
  3. Nemcok, M., Schamel, S. & Gayer, R. 2005. Thrustbelts - Structural Architecture, Thermal Regimes and Petroleum Systems. Cambridge University Press ISBN 978-0-521-82294-7
  4. THE EVOLUTION OF THE ALTIPLANO-PUNA PLATEAU OF THE CENTRAL ANDES. 1997.


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