Monocline
A monocline (or, rarely, a monoform) is a step-like fold in rock strata consisting of a zone of steeper dip within an otherwise horizontal or gently-dipping sequence.
block diagram of a monocline
The Grandview-Phantom Monocline in the Grand Canyon, Arizona
Monocline at Colorado National Monument
Monocline formed at tip of small thrust fault, Brims Ness, Caithness, Scotland
Formation
Possible modes of formation of monoclines
Monoclines may be formed in several different ways (see diagram)
- By differential compaction over an underlying structure, particularly a large fault at the edge of a basin due to the greater compactibility of the basin fill, the amplitude of the fold will die out gradually upwards.[1]
- By mild reactivation of an earlier extensional fault during a phase of inversion causing folding in the overlying sequence.[2]
- As a form of fault propagation fold during upward propagation of an extensional fault in basement into an overlying cover sequence.[3]
- As a form of fault propagation fold during upward propagation of a reverse fault in basement into an overlying cover sequence.[4]
Examples
- Waterpocket Fold in Capitol Reef National Park, Utah[5]
- Grandview-Phantom Monocline in Grand Canyon, Arizona[6]
- Grand Hogback in Colorado[7]
- Lebombo Mountains in Southern Africa[8]
- Lapstone Monocline in the Blue Mountains (Australia)[9]
- Beaumaris Monocline in Victoria (Australia)[10]
- Purbeck Monocline on the Isle of Purbeck, Dorset, England[11]
- Fore-Sudetic Monocline, Poland[12]
- Sindh Monocline, Pakistan[13]
- Torres Flexure, southern Brazil[14]
References
- Skuce, A.G. (1996). "Forward modelling of compaction above normal faults: an example from the Sirte Basin, Libya" (PDF). In Buchanan, P.G.; Nieuwland, D.A. (eds.). Modern Developments in Structural Interpretation, Validation and Modelling. Special Publications. 99. London: Geological Society. pp. 135–146. ISBN 978-1-897799-43-7. Archived from the original (PDF) on 2012-03-16.
- Chadwick, R.A. (1993). "Aspects of basin inversion in southern Britain". Journal of the Geological Society. 150 (2): 311–322. Bibcode:1993JGSoc.150..311C. doi:10.1144/gsjgs.150.2.0311.
- Willsey, S.P.; Umhoefer, P.J.; Hilley, G.E. (2002). "Early evolution of an extensional monocline by a propagating normal fault: 3D analysis from combined field study and numerical modeling" (PDF). Journal of Structural Geology. 24 (4): 651–669. Bibcode:2002JSG....24..651W. doi:10.1016/S0191-8141(01)00120-1. Archived from the original (PDF) on 2011-07-20. Retrieved 2011-01-09.
- Finch, E.; Hardy, S.; Gawthorpe, R. (2003). "Discrete element modelling of contractional fault-propagation folding above rigid basement fault blocks". Journal of Structural Geology. 25 (4): 515–528. Bibcode:2003JSG....25..515F. doi:10.1016/S0191-8141(02)00053-6.
- "Geology". Capitol Reef National Park. National Park Service. 23 December 2017. Retrieved 1 March 2018.
- Abbott, Lon; Cook, Terri (2004). Hiking the Grand Canyon's Geology. Seattle: The Mountaineers Books. pp. 99–114. ISBN 978-0-89886-895-1.
- Murray, Frederick N. (1967). "Jointing in Sedimentary Rocks along the Grand Hogback Monocline, Colorado". The Journal of Geology. 75 (3): 340–350. doi:10.1086/627261. JSTOR 30071521.
- Klausen, M.B. (2009). "The Lebombo monocline and associated feeder dyke swarm: Diagnostic of a successful and highly volcanic rifted margin?". Tectonophysics. 468 (1–4): 42–62. Bibcode:2009Tectp.468...42K. doi:10.1016/j.tecto.2008.10.012.
- "L001 : Lapstone Monocline". Heritage places and items. Office of Environment and Heritage, Government of New South Wales. Retrieved 1 March 2018.
- "61. Beaumaris Cliffs 3 - Monocline". Sites of Geological and Geomorphological Significance. Agriculture Victoria. 8 June 2017. Retrieved 1 March 2018.
- Nowell, D.A.G. (1997). "Structures affecting the coast around Lulworth Cove, Dorset and syn-sedimentary Wealden faulting". Proceedings of the Geologists' Association. 108 (4): 257–268. doi:10.1016/S0016-7878(97)80011-9.
- Kluska, B.; Rospondek, M.J.; Marynowski, L.; Schaeffer, P. (2013). "The Werra cyclotheme (Upper Permian, Fore-Sudetic Monocline, Poland): Insights into fluctuations of the sedimentary environment from organic geochemical studies". Applied Geochemistry. 29: 73–91. Bibcode:2013ApGC...29...73K. doi:10.1016/j.apgeochem.2012.09.010.
- Memon, A.D.; Siddiqui, I.; Memon, A. (1999). "Tectonics of the Sindh monocline, Pakistan and their effects on hydrocarbons". Mehran University Research Journal of Engineering and Technology. 18 (2): 87–96.
- Seth, H. (2018). Tectonic Deformation of Flood Basalt Provinces. Springer. ISBN 978-3-319-67704-0.
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