Monocline
Encyclopedia
A monocline is a step-like fold
in rock strata
consisting of a zone of steeper dip
within an otherwise horizontal or gently-dipping sequence.
Monoclines may be formed in several different ways (see diagram)
Fold (geology)
The term fold is used in geology when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of permanent deformation. Synsedimentary folds are those due to slumping of sedimentary material before it is lithified. Folds in rocks vary in...
in rock strata
Stratum
In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...
consisting of a zone of steeper dip
Strike and dip
Strike and dip refer to the orientation or attitude of a geologic feature. The strike line of a bed, fault, or other planar feature is a line representing the intersection of that feature with a horizontal plane. On a geologic map, this is represented with a short straight line segment oriented...
within an otherwise horizontal or gently-dipping sequence.
Formation
- By differential compactionCompaction (geology)Compaction refers to the process by which a sediment progressively loses its porosity due to the effects of loading. This forms part of the process of lithification. When a layer of sediment is originally deposited, it contains an open framework of particles with the pore space being usually...
over an underlying structure, particularly a large fault at the edge of a basinSedimentary basinThe term sedimentary basin is used to refer to any geographical feature exhibiting subsidence and consequent infilling by sedimentation. As the sediments are buried, they are subjected to increasing pressure and begin the process of lithification...
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 faultExtensional faultAn extensional fault is a fault that vertically thins and horizontally extends portions of the Earth's crust and/or lithosphere. In most cases such a fault is also a normal fault, but may be rotated to have a shallower geometry normally associated with a thrust fault...
during a phase of inversionInversion (geology)In structural geology inversion or basin inversion relates to the relative uplift of a sedimentary basin or similar structure as a result of crustal shortening. This normally excludes uplift developed in the footwalls of later extensional faults, or uplift caused by mantle plumes...
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.
Examples
- Waterpocket FoldWaterpocket FoldThe Waterpocket Fold is a geologic landform that defines Capitol Reef National Park in the western United States. This monoclinal fold extends for slightly over 100 miles in the desert of central Utah. It can be seen via three scenic routes in the park. One route leads to a famous landmark known as...
in Capitol Reef National ParkCapitol Reef National ParkCapitol Reef National Park is a United States National Park, in south-central Utah. It is 100 miles long but fairly narrow. The park, established in 1971, preserves 378 mi² and is open all year, although May through September are the most popular months.Called "Wayne Wonderland" in the 1920s...
, UtahUtahUtah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the... - Grandview-Phantom Monocline in the Grand CanyonGrand CanyonThe Grand Canyon is a steep-sided canyon carved by the Colorado River in the United States in the state of Arizona. It is largely contained within the Grand Canyon National Park, the 15th national park in the United States...
, ArizonaArizonaArizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix... - Lapstone monocline in the Blue Mountains (Australia)
- Purbeck MonoclinePurbeck MonoclineThe Purbeck Monocline is a geological fold. The term 'fold' is used in geology when one or more originally flat sedimentary strata surfaces are bent or curved as a result of plastic deformation. A monocline is a step-like fold, in which one limb is roughly horizontal...
on the Isle of PurbeckIsle of PurbeckThe Isle of Purbeck, not a true island but a peninsula, is in the county of Dorset, England. It is bordered by the English Channel to the south and east, where steep cliffs fall to the sea; and by the marshy lands of the River Frome and Poole Harbour to the north. Its western boundary is less well...
, DorsetDorsetDorset , is a county in South West England on the English Channel coast. The county town is Dorchester which is situated in the south. The Hampshire towns of Bournemouth and Christchurch joined the county with the reorganisation of local government in 1974...
, EnglandEnglandEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...