Monocline

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 monocline

The Grandview-Phantom Monocline in the Grand Canyon, Arizona

Monocline at Colorado National Monument

Monocline formed at tip of small thrust fault, Brims Ness, Caithness, Scotland

Formation

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]

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