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 monoclineThe Grandview-Phantom Monocline in the Grand Canyon, ArizonaMonocline at Colorado National MonumentMonocline formed at tip of small thrust fault, Brims Ness, Caithness, Scotland
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]
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. Bibcode:1997PrGA..108..257N. doi:10.1016/S0016-7878(97)80011-9.