Monocline
{{Short description|Geological structure}}
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File:Grandview-Phantom_Monocline.jpg, Arizona]]
File:Minor thrust monocline.JPG, Scotland]]
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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
File:MonoclineMonoclinalFr02.gif
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.{{Cite book|last=Skuce|first=A.G.|year=1996|chapter=Forward modelling of compaction above normal faults: an example from the Sirte Basin, Libya|editor=Buchanan, P.G.|editor2=Nieuwland, D.A.|title=Modern Developments in Structural Interpretation, Validation and Modelling|publisher=Geological Society|location=London|series=Special Publications|volume=99|pages=135–146|isbn=978-1-897799-43-7|chapter-url=http://s-s-consulting.com/pdf_articles/geol%20soc%201996.pdf|url-status=dead|archive-url=https://web.archive.org/web/20120316235528/http://s-s-consulting.com/pdf_articles/geol%20soc%201996.pdf|archive-date=2012-03-16}}
- By mild reactivation of an earlier extensional fault during a phase of inversion causing folding in the overlying sequence.{{Cite journal|last=Chadwick|first=R.A.|date=1993|title= Aspects of basin inversion in southern Britain|journal= Journal of the Geological Society|volume= 150|issue=2|pages= 311–322|doi=10.1144/gsjgs.150.2.0311|url=http://jgs.lyellcollection.org/cgi/content/abstract/150/2/311?ijkey=075ea7d0d92cd14125f610d8bc8feed0be8fb091&keytype2=tf_ipsecsha|bibcode=1993JGSoc.150..311C|s2cid=131396080}}
- As a form of fault propagation fold during upward propagation of an extensional fault in basement into an overlying cover sequence.{{Cite journal|last=Willsey|first=S.P.|author2=Umhoefer, P.J.|author3=Hilley, G.E.|date=2002|title=Early evolution of an extensional monocline by a propagating normal fault: 3D analysis from combined field study and numerical modeling|journal=Journal of Structural Geology|volume=24|issue=4|pages=651–669|url=http://earthsciences.stanford.edu/research/geomech/Software/publications/Willsey_JSG_2002.pdf|doi=10.1016/S0191-8141(01)00120-1|bibcode=2002JSG....24..651W|access-date=2011-01-09|archive-url=https://web.archive.org/web/20110720045336/http://earthsciences.stanford.edu/research/geomech/Software/publications/Willsey_JSG_2002.pdf|archive-date=2011-07-20|url-status=dead}}
- As a form of fault propagation fold during upward propagation of a reverse fault in basement into an overlying cover sequence.{{Cite journal|last=Finch|first=E. |author2=Hardy, S. |author3=Gawthorpe, R. |date=2003|title= Discrete element modelling of contractional fault-propagation folding above rigid basement fault blocks|journal= Journal of Structural Geology|volume= 25|issue=4 |pages= 515–528|doi=10.1016/S0191-8141(02)00053-6 |bibcode = 2003JSG....25..515F }}
Examples
- Waterpocket Fold in Capitol Reef National Park, Utah{{cite web | url=https://www.nps.gov/care/learn/nature/geology.htm | title=Geology | publisher=National Park Service | work=Capitol Reef National Park | date=23 December 2017 | access-date=1 March 2018}}
- Comb Ridge in southern Utah{{Cite web|date=2019-11-24|title=Comb Ridge, Utah|url=https://earthobservatory.nasa.gov/images/145913/comb-ridge-utah|access-date=2021-10-22|website=earthobservatory.nasa.gov|language=en}}
- Grandview-Phantom Monocline in Grand Canyon, Arizona{{cite book | title=Hiking the Grand Canyon's Geology | publisher=The Mountaineers Books | last1=Abbott |first1=Lon |last2=Cook |first2= Terri | year=2004 | location=Seattle | pages=99–114 | isbn=978-0-89886-895-1}}
- Grand Hogback in Colorado{{cite journal | title=Jointing in Sedimentary Rocks along the Grand Hogback Monocline, Colorado | author=Murray, Frederick N. | journal=The Journal of Geology | year=1967 | volume=75 | issue=3 | pages=340–350|jstor = 30071521| doi=10.1086/627261 | bibcode=1967JG.....75..340M | s2cid=128672429 }}
- Lebombo Mountains in Southern Africa{{cite journal | title=The Lebombo monocline and associated feeder dyke swarm: Diagnostic of a successful and highly volcanic rifted margin? | author=Klausen, M.B. | journal=Tectonophysics | year=2009 | volume=468 | issue=1–4 | pages=42–62 | doi=10.1016/j.tecto.2008.10.012| bibcode=2009Tectp.468...42K }}
- Lapstone Monocline in the Blue Mountains (Australia){{cite web | url=http://www.environment.nsw.gov.au/heritageapp/ViewHeritageItemDetails.aspx?ID=1170643 | title=L001 : Lapstone Monocline | publisher=Office of Environment and Heritage, Government of New South Wales | work=Heritage places and items | access-date=1 March 2018}}
- Beaumaris Monocline in Victoria (Australia){{cite web | url=http://vro.agriculture.vic.gov.au/dpi/vro/portregn.nsf/pages/port_lf_sig_sites_beaumaris3 | title=61. Beaumaris Cliffs 3 - Monocline | publisher=Agriculture Victoria | work=Sites of Geological and Geomorphological Significance | date=8 June 2017 | access-date=1 March 2018}}
- Purbeck Monocline on the Isle of Purbeck, Dorset, England{{cite journal | title=Structures affecting the coast around Lulworth Cove, Dorset and syn-sedimentary Wealden faulting | author=Nowell, D.A.G. | journal=Proceedings of the Geologists' Association | year=1997 | volume=108 | issue=4 | pages=257–268 | doi=10.1016/S0016-7878(97)80011-9| bibcode=1997PrGA..108..257N }}
- Fore-Sudetic Monocline, Poland{{cite journal | title=The Werra cyclotheme (Upper Permian, Fore-Sudetic Monocline, Poland): Insights into fluctuations of the sedimentary environment from organic geochemical studies | first1=B. | last1=Kluska | first2=M.J. | last2=Rospondek | first3=L. | last3=Marynowski | first4=P. | last4=Schaeffer | journal=Applied Geochemistry | year=2013 | volume=29 | pages=73–91 | doi=10.1016/j.apgeochem.2012.09.010| bibcode=2013ApGC...29...73K }}
- Sindh Monocline, Pakistan{{cite journal | url=https://inis.iaea.org/search/searchsinglerecord.aspx?recordsFor=SingleRecord&RN=30035671 | title=Tectonics of the Sindh monocline, Pakistan and their effects on hydrocarbons | last1=Memon | first1=A.D. | last2=Siddiqui | first2=I. | last3=Memon | first3=A. | journal=Mehran University Research Journal of Engineering and Technology | year=1999 | volume=18 | issue=2 | pages=87–96}}
- Torres Flexure, southern Brazil{{cite book | url=https://www.springerprofessional.de/en/tectonic-deformation-of-flood-basalt-provinces/15254768 | title=Tectonic Deformation of Flood Basalt Provinces | publisher=Springer | author=Seth, H. | year=2018 | isbn=978-3-319-67704-0}}