Nappe
In geology, a nappe or thrust sheet is a large sheetlike body of rock that has been moved more than 2 km (1.2 mi)[1] or 5 km (3.1 mi)[2][3] above a thrust fault from its original position. Nappes form in compressional tectonic settings like continental collision zones or on the overriding plate in active subduction zones. Nappes form when a mass of rock is forced (or "thrust") over another rock mass, typically on a low angle fault plane. The resulting structure may include large-scale recumbent folds, shearing along the fault plane,[4] imbricate thrust stacks, fensters and klippes.
The term stems from the French word for tablecloth in allusion to a rumpled tablecloth being pushed across a table.[4]
History
Nappes or nappe belts are a major feature of the
Structure
Nappe can be qualified in a number of ways to indicate various features of a formation. The frontal part in the direction of movement, is called the leading edge of a nappe; numerous
Areas with a nappe structure often contain two types of geological features:
- A nappe outlier or klippe is a small area isolated from the main body of the nappe by erosion that lies on the autochthonous base; the summit of Veľký Rozsutec in the Western Carpathians is a typical example.
- A fault inlier, fenster, or window is an area of the autochthonous basement uncovered by erosion, but entirely surrounded by the body of the nappe; the Hohe Tauern window in the Alps is a typical example.
Classification
According to petrographical composition, two basic types of nappes are known:
- Penninic nappes.
- crust, forming so-called thin-skinned style. Therefore, nappes of this type form smaller units, such as the Hallstatt nappe in the Austroalpine nappesof the Alps.
Mechanisms of emplacement
Nappes are generally considered as compressional structures, however some exceptions could be found especially among the gravitational slides along low angle faults.[8][9] Gravitational forces could even be important in certain cases during emplacement of compressional thrusts. The movement of huge masses of rock may be influenced by several forces, forces that may act together or sequentially. These forces frequently result in high temperature and pressure metamorphism and strong deformation of nappe rocks.[10]
At shallower depths, low
Behavior of
References
- ^ Howell, J.V. (Editor) 1960: Glossary of geology and related sciences. American Geological Institute, Washington D.C., 325 p.
- ISBN 80-88896-36-3Vydavateľstvo Harlequin, Košice, p. 81 - 93 (in Slovak)
- ^ Dennis, J. G., 1967, International tectonic dictionary. AAPG, Tulsa, p. 112
- ^ ISBN 978-0716722526
- ^ Schmid, S. M., Fügenschuh, B., Kissling, E, and Schuster, R. 2004: Tectonic Map and Overall Architecture of the Alpine Orogen. Archived 2012-01-12 at the Wayback Machine Eclogae geologicae Helvetiae v. 97, Basel: Birkhäuser Verlag, pp. 93–117, ISSN 0012-9402
- ^ Gamkrelidze, I.P. 1991: Tectonic nappes and horizontal layering of the Earth’s crust in the Mediterranean belt (Carpathians, Balkanides and Caucasus). Tectonophysics, 196, p. 385-396
- ^ Franks, S., Trümpy, R., 2005: The Sixth International Geological Congress: Zürich, 1894. Episodes, vol. 28, 3, p. 187-192
- ISBN 978-0-632-00614-4
- ISBN 978-0-7487-5802-9.
- ^ Rodrigues, S. W. O., Martins-Ferreira, M. A. C., Faleiros, F. M., Neto, M. D. C. C., & Yogi, M. T. A. G. (2019). Deformation conditions and quartz c-axis fabric development along nappe boundaries: The Andrelândia Nappe System, Southern Brasília Orogen (Brazil). Tectonophysics.
- ^ Davis, D.M., Engelder, T., 1985: The role of salt in fold-and-thrust belts. Tectonophysics, 119, p. 67-88
- ^ Nemčok, M., Schamel, S., Gayer, R. A., 2005: Thrustbelts: structural architecture, thermal regimes and petroleum systems. Cambridge University Press, Cambridge, 554 p.
- ^ Price, N.J., McClay, K.R., 1981: Introduction. p. 1-5 in Price, N.J., McClay, K.R. (Eds.), Thrust and Nappe Tectonics. Geological Society, Special Publications vol. 9, London, 528 p.
