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.
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.
Monoclines may be formed in several different ways (see diagram)
A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks.
In structural geology, a fold is a stack of originally planar surfaces, such as sedimentary strata, that are bent or curved during permanent deformation. Folds in rocks vary in size from microscopic crinkles to mountain-sized folds. They occur as single isolated folds or in periodic sets. Synsedimentary folds are those formed during sedimentary deposition.
Mylonite is a fine-grained, compact metamorphic rock produced by dynamic recrystallization of the constituent minerals resulting in a reduction of the grain size of the rock. Mylonites can have many different mineralogical compositions; it is a classification based on the textural appearance of the rock.
A dome is a feature in structural geology consisting of symmetrical anticlines that intersect each other at their respective apices. Intact, domes are distinct, rounded, spherical-to-ellipsoidal-shaped protrusions on the Earth's surface. However, a transect parallel to Earth's surface of a dome features concentric rings of strata. Consequently, if the top of a dome has been eroded flat, the resulting structure in plan view appears as a bullseye, with the youngest rock layers at the outside, and each ring growing progressively older moving inwards. These strata would have been horizontal at the time of deposition, then later deformed by the uplift associated with dome formation.
The Moab Fault, near Moab, Utah, United States, is an extensional fault that runs approximately NW-SE, passing to the west of the Arches National Park. It is about 45 km (28 mi) long and has a maximum displacement of about 960 m (3,150 ft). The fault connects with the Tenmile graben in the north and extends through the Moab-Spanish Valley to the south. The fault outcrop has a well-defined fault zone bordered by a damage zone of minor faults and fractures.
Extensional tectonics is concerned with the structures formed by, and the tectonic processes associated with, the stretching of a planetary body's crust or lithosphere.
Strike-slip tectonics or wrench tectonics is a type of tectonics that is dominated by lateral (horizontal) movements within the Earth's crust. Where a zone of strike-slip tectonics forms the boundary between two tectonic plates, this is known as a transform or conservative plate boundary. Areas of strike-slip tectonics are characterised by particular deformation styles including: stepovers, Riedel shears, flower structures and strike-slip duplexes. Where the displacement along a zone of strike-slip deviates from parallelism with the zone itself, the style becomes either transpressional or transtensional depending on the sense of deviation. Strike-slip tectonics is characteristic of several geological environments, including oceanic and continental transform faults, zones of oblique collision and the deforming foreland of zones of continental collision.
Salt tectonics, or halokinesis, or halotectonics, is concerned with the geometries and processes associated with the presence of significant thicknesses of evaporites containing rock salt within a stratigraphic sequence of rocks. This is due both to the low density of salt, which does not increase with burial, and its low strength.
In structural geology and diagenesis, pressure solution or pressure dissolution is a deformation mechanism that involves the dissolution of minerals at grain-to-grain contacts into an aqueous pore fluid in areas of relatively high stress and either deposition in regions of relatively low stress within the same rock or their complete removal from the rock within the fluid. It is an example of diffusive mass transfer.
In structural geology section restoration or palinspastic restoration is a technique used to progressively undeform a geological section in an attempt to validate the interpretation used to build the section. It is also used to provide insights into the geometry of earlier stages of the geological development of an area. A section that can be successfully undeformed to a geologically reasonable geometry, without change in area, is known as a balanced section.
The Purbeck Monocline is a geological fold in southern England. 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. The Purbeck Monocline was formed during the late Oligocene and early Miocene epochs, about 30 million years ago. It is the northernmost 'ripple' of the Alpine Orogeny.
The Zagros fold and thrust belt is an approximately 1,800-kilometre (1,100 mi) long zone of deformed crustal rocks, formed in the foreland of the collision between the Arabian Plate and the Eurasian Plate. It is host to one of the world's largest petroleum provinces, containing about 49% of the established hydrocarbon reserves in fold and thrust belts (FTBs) and about 7% of all reserves globally.
The geology of the Isle of Wight is dominated by sedimentary rocks of Cretaceous and Paleogene age. This sequence was affected by the late stages of the Alpine Orogeny, forming the Isle of Wight monocline, the cause of the steeply-dipping outcrops of the Chalk Group and overlying Paleogene strata seen at The Needles, Alum Bay and Whitecliff Bay.
The Karakoram fault is an oblique-slip fault system in the Himalayan region across India and Asia. The slip along the fault accommodates radial expansion of the Himalayan arc, northward indentation of the Pamir Mountains, and eastward lateral extrusion of the Tibetan plateau. Current plate motions suggest that the convergence between the Indian Plate and the Eurasian Plate is around 44±5 mm per year in the western Himalaya-Pamir region and approximately 50±2 mm per year in the eastern Himalayan region.
Strain partitioning is commonly referred to as a deformation process in which the total strain experienced on a rock, area, or region, is heterogeneously distributed in terms of the strain intensity and strain type. This process is observed on a range of scales spanning from the grain – crystal scale to the plate – lithospheric scale, and occurs in both the brittle and plastic deformation regimes. The manner and intensity by which strain is distributed are controlled by a number of factors listed below.
The Wessex Basin is a petroleum-bearing geological area located along the southern coast of England and extending into the English Channel. The onshore part of the basin covers approximately 20,000 km2 and the area that encompasses the English Channel is of similar size. The basin is a rift basin that was created during the Permian to early Cretaceous in response to movement of the African plate relative to the Eurasian plate. In the late Cretaceous, and again in the Cenozoic, the basin was inverted as a distant effect of the Alpine orogeny. The basin is usually divided into 3 main sub-basins including the Winterborne-Kingston Trough, Channel Basin, and Vale of Pewsey Basin. The area is also rich in hydrocarbons with several offshore wells in the area. With the large interest in the hydrocarbon exploration of the area, data became more readily available, which improved the understanding of the type of inversion tectonics that characterize this basin.
This is a compilation of the properties of different analog materials used to simulate deformational processes in structural geology. Such experiments are often called analog or analogue models. The organization of this page follows the review of rock analog materials in structural geology and tectonics of Reber et al. 2020.
The Junggar Basin is one of the largest sedimentary basins in Northwest China. It is located in Xinjiang, and enclosed by the Tarbagatai Mountains of Kazakhstan in the northwest, the Altai Mountains of Mongolia in the northeast, and the Heavenly Mountains in the south. The geology of Junggar Basin mainly consists of sedimentary rocks underlain by igneous and metamorphic basement rocks. The basement of the basin was largely formed during the development of the Pangea supercontinent during complex tectonic events from Precambrian to late Paleozoic time. The basin developed as a series of foreland basins – in other words, basins developing immediately in front of growing mountain ranges – from Permian time to the Quaternary period. The basin's preserved sedimentary records show that the climate during the Mesozoic era was marked by a transition from humid to arid conditions as monsoonal climatic effects waned. The Junggar basin is rich in geological resources due to effects of volcanism and sedimentary deposition. According to Guinness World Records it is a land location remotest from open sea with great-circle distance of 2,648 km from the nearest open sea at 46°16′8″N86°40′2″E.
Patience Anne Cowie was a Professor of Earth System Dynamics at the University of Bergen. Her research has considered fault propagation and rift basins. She was awarded the 2016 Geological Society of London Coke medal.
A steep structure is a unique structural feature found in the O'okiep Copper District (OCD), Namaqualand, Northern Cape Province, South Africa. These structures occur as narrow, east-west trending, antiformal and/or monoclinal zones of high strain characterised by the rotation of regional foliation into subvertical attitude. These structures commonly host plug- and dyke-like mafic- to intermediate cupriferous bodies of the Koperberg Suite in their central portions. Steep structures are interpreted to have formed at the same time as the granulite-facies metamorphism during the waning stages of the Namaqua Orogeny. Steep structures are also intimately related to megabreccias, a term coined by geologists in the OCD for granite-gneiss and metasedimentary country rocks cemented by granitic material
