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block diagram of a monocline
The Grandview-Phantom Monocline in the Grand Canyon, Arizona
Monocline formed at tip of small thrust fault, Brims Ness, Caithness, Scotland

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.


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]


See also[edit]


  1. ^ Skuce, A.G. (1996). "Forward modelling of compaction above normal faults: an example from the Sirte Basin, Libya". In Buchanan,P.G.; Nieuwland,D.A. Modern Developments in Structural Interpretation, Validation and Modelling (PDF). Special Publications. 99. London: Geological Society. pp. 135–146. ISBN 978-1-897799-43-7. 
  2. ^ Chadwick, R.A. (1993). "Aspects of basin inversion in southern Britain". Journal of the Geological Society. 150: 311–322. doi:10.1144/gsjgs.150.2.0311. 
  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" (PDF). Journal of Structural Geology. 24: 651–669. Bibcode:2002JSG....24..651W. doi:10.1016/S0191-8141(01)00120-1. 
  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: 515–528. Bibcode:2003JSG....25..515F. doi:10.1016/S0191-8141(02)00053-6. 

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