block diagram of a monocline
The Grandview-Phantom Monocline in the Grand Canyon
Monocline formed at tip of small thrust fault, Brims Ness, Caithness
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.
- By mild reactivation of an earlier extensional fault during a phase of inversion causing folding in the overlying sequence.
- As a form of fault propagation fold during upward propagation of an extensional fault in basement into an overlying cover sequence.
- As a form of fault propagation fold during upward propagation of a reverse fault in basement into an overlying cover sequence.