Monocline Explained

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.

Formation

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]
• Comb Ridge in southern Utah^[6]
• Grandview-Phantom Monocline in Grand Canyon, Arizona^[7]
• Grand Hogback in Colorado^[8]
• Lebombo Mountains in Southern Africa^[9]
• Lapstone Monocline in the Blue Mountains (Australia)^[10]
• Beaumaris Monocline in Victoria (Australia)^[11]
• Purbeck Monocline on the Isle of Purbeck, Dorset, England^[12]
• Fore-Sudetic Monocline, Poland^[13]
• Sindh Monocline, Pakistan^[14]
• Torres Flexure, southern Brazil^[15]

See also

• Anticline
• Homocline
• Syncline

Notes and References

1. Book: Skuce, A.G.. 1996. Forward modelling of compaction above normal faults: an example from the Sirte Basin, Libya. Buchanan, P.G.. Nieuwland, D.A.. Modern Developments in Structural Interpretation, Validation and Modelling. Geological Society. London. Special Publications. 99. 135–146. 978-1-897799-43-7. http://s-s-consulting.com/pdf_articles/geol%20soc%201996.pdf. dead. https://web.archive.org/web/20120316235528/http://s-s-consulting.com/pdf_articles/geol%20soc%201996.pdf. 2012-03-16.
2. Chadwick. R.A.. 1993. Aspects of basin inversion in southern Britain. Journal of the Geological Society. 150. 2. 311–322. 10.1144/gsjgs.150.2.0311. 1993JGSoc.150..311C. 131396080.
3. 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. Journal of Structural Geology. 24. 4. 651–669. 10.1016/S0191-8141(01)00120-1. 2002JSG....24..651W. 2011-01-09. https://web.archive.org/web/20110720045336/http://earthsciences.stanford.edu/research/geomech/Software/publications/Willsey_JSG_2002.pdf. 2011-07-20. dead.
4. 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. 10.1016/S0191-8141(02)00053-6 . 2003JSG....25..515F .
5. Web site: Geology . . Capitol Reef National Park . 23 December 2017 . 1 March 2018.
6. Web site: 2019-11-24. Comb Ridge, Utah. 2021-10-22. earthobservatory.nasa.gov. en.
7. Book: Hiking the Grand Canyon's Geology . The Mountaineers Books . Abbott . Lon . Cook . Terri . 2004 . Seattle . 99–114 . 978-0-89886-895-1.
8. Jointing in Sedimentary Rocks along the Grand Hogback Monocline, Colorado . Murray, Frederick N. . The Journal of Geology . 1967 . 75 . 3 . 340–350. 30071521. 10.1086/627261 . 1967JG.....75..340M . 128672429 .
9. The Lebombo monocline and associated feeder dyke swarm: Diagnostic of a successful and highly volcanic rifted margin? . Klausen, M.B. . Tectonophysics . 2009 . 468 . 1–4 . 42–62 . 10.1016/j.tecto.2008.10.012. 2009Tectp.468...42K .
10. Web site: L001 : Lapstone Monocline . . Heritage places and items . 1 March 2018.
11. Web site: 61. Beaumaris Cliffs 3 - Monocline . Agriculture Victoria . Sites of Geological and Geomorphological Significance . 8 June 2017 . 1 March 2018.
12. Structures affecting the coast around Lulworth Cove, Dorset and syn-sedimentary Wealden faulting . Nowell, D.A.G. . Proceedings of the Geologists' Association . 1997 . 108 . 4 . 257–268 . 10.1016/S0016-7878(97)80011-9. 1997PrGA..108..257N .
13. The Werra cyclotheme (Upper Permian, Fore-Sudetic Monocline, Poland): Insights into fluctuations of the sedimentary environment from organic geochemical studies . B. . Kluska . M.J. . Rospondek . L. . Marynowski . P. . Schaeffer . Applied Geochemistry . 2013 . 29 . 73–91 . 10.1016/j.apgeochem.2012.09.010. 2013ApGC...29...73K .
14. Tectonics of the Sindh monocline, Pakistan and their effects on hydrocarbons . Memon . A.D. . Siddiqui . I. . Memon . A. . Mehran University Research Journal of Engineering and Technology . 1999 . 18 . 2 . 87–96.
15. Book: Tectonic Deformation of Flood Basalt Provinces . Springer . Seth, H. . 2018 . 978-3-319-67704-0.