Foreland basin

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The Persian Gulf - the foreland basin produced by the Zagros orogenic belt PersianGulf vue satellite du golfe persique.jpg
The Persian Gulf – the foreland basin produced by the Zagros orogenic belt

A foreland basin is a structural basin that develops adjacent and parallel to a mountain belt. Foreland basins form because the immense mass created by crustal thickening associated with the evolution of a mountain belt causes the lithosphere to bend, by a process known as lithospheric flexure. The width and depth of the foreland basin is determined by the flexural rigidity of the underlying lithosphere, and the characteristics of the mountain belt. The foreland basin receives sediment that is eroded off the adjacent mountain belt, filling with thick sedimentary successions that thin away from the mountain belt. Foreland basins represent an endmember basin type, the other being rift basins. Space for sediments (accommodation space) is provided by loading and downflexure to form foreland basins, in contrast to rift basins, where accommodation space is generated by lithospheric extension.

Contents

Types of foreland basin

Foreland Basin Classes: Peripheral vs. Retroarc Peripheralvs.Retroarc.png
Foreland Basin Classes: Peripheral vs. Retroarc

Foreland basins can be divided into two categories:

Foreland basin system

The Foreland Basin System ForelandBasinSystem.png
The Foreland Basin System

DeCelles & Giles (1996) provide a thorough definition of the foreland basin system. Foreland basin systems comprise three characteristic properties:

  1. An elongate region of potential sediment accommodation that forms on continental crust between a contractional orogenic belt and the adjacent craton, mainly in response to geodynamic processes related to subduction and the resulting peripheral or retroarc fold-thrust belt;
  2. It consists of four discrete depozones, referred to as the wedge-top, foredeep, forebulge and back-bulge depozones (depositional zones) – which of these depozones a sediment particle occupies depends on its location at the time of deposition, rather than its ultimate geometric relationship with the thrust belt;
  3. The longitudinal dimension of the foreland basin system is roughly equal to the length of the fold-thrust belt, and does not include sediment that spills into remnant ocean basins or continental rifts (impactogens).

Foreland basin systems: depozones

The wedge-top sits on top of the moving thrust sheets and contains all the sediments charging from the active tectonic thrust wedge. This is where piggyback basins form.

The foredeep is the thickest sedimentary zone and thickens toward the orogen. Sediments are deposited via distal fluvial, lacustrine, deltaic, and marine depositional systems.

The forebulge and backbulge are the thinnest and most distal zones and are not always present. When present, they are defined by regional unconformities as well as aeolian and shallow-marine deposits.

Sedimentation is most rapid near the moving thrust sheet. Sediment transport within the foredeep is generally parallel to the strike of the thrust fault and basin axis.

Plate motion and seismicity

The motion of the adjacent plates of the foreland basin can be determined by studying the active deformation zone with which it is connected. Today GPS measurements provide the rate at which one plate is moving relative to another. It is also important to consider that present day kinematics are unlikely to be the same as when deformation began. Thus, it is crucial to consider non-GPS models to determine the long-term evolution of continental collisions and in how it helped develop the adjacent foreland basins.

Comparing both modern GPS (Sella et al. 2002) and non-GPS models allows deformation rates to be calculated. Comparing these numbers to the geologic regime helps constrain the number of probable models as well as which model is more geologically accurate within a specific region.

Seismicity determines where active zones of seismic activity occur as well as measure the total fault displacements and the timing of the onset of deformation. [1]

Formation of basins

Generalized Foreland Basin System Evolution ForelandBasinEvolution.png
Generalized Foreland Basin System Evolution

Foreland basins form because as the mountain belt grows, it exerts a significant mass on the Earth's crust, which causes it to bend, or flex, downwards. This occurs so that the weight of the mountain belt can be compensated by isostasy at the upflex of the forebulge.

The plate tectonic evolution of a peripheral foreland basin involves three general stages. First, the passive margin stage with orogenic loading of previously stretched continental margin during the early stages of convergence. Second, the "early convergence stage defined by deep water conditions", and lastly a "later convergent stage during which a subaerial wedge is flanked with terrestrial or shallow marine foreland basins". [2] [ page needed ]

The temperature underneath the orogen is much higher and weakens the lithosphere. Thus, the thrust belt is mobile and the foreland basin system becomes deformed over time. Syntectonic unconformities demonstrate simultaneous subsidence and tectonic activity.

Foreland basins are filled with sediments which erode from the adjacent mountain belt. In the early stages, the foreland basin is said to be underfilled. During this stage, deep water and commonly marine sediments, known as flysch, are deposited. Eventually, the basin becomes completely filled. At this point, the basin enters the overfilled stage and deposition of terrestrial clastic sediments occurs. These are known as molasse. Sediment fill within the foredeep acts as an additional load on the continental lithosphere.[ citation needed ]

Lithospheric behavior

Moving Load System - Lithospheric flexure over time Viscoelastic lithospheric flexure.png
Moving Load System – Lithospheric flexure over time

Although the degree to which the lithosphere relaxes over time is still controversial, most workers [2] [ page needed ] [3] accept an elastic or visco-elastic rheology to describe the lithospheric deformation of the foreland basin. Allen & Allen (2005) describe a moving load system, one in which the deflection moves as a wave through the foreland plate before the load system. The deflection shape is commonly described as an asymmetrical low close to the load along the foreland and a broader uplifted deflection along the forebulge. The transport rate or flux of erosion, as well as sedimentation, is a function of topographic relief.

For the loading model, the lithosphere is initially stiff, with the basin broad and shallow. Relaxation of the lithosphere allows subsidence near the thrust, narrowing of basin, forebulge toward thrust. During times of thrusting, the lithosphere is stiff and the forebulge broadens. The timing of the thrust deformation is opposite that of the relaxing of the lithosphere. The bending of the lithosphere under the orogenic load controls the drainage pattern of the foreland basin. The flexural tilting of the basin and the sediment supply from the orogen.

Lithospheric strength envelopes

Strength envelopes indicate that the rheological structure of the lithosphere underneath the foreland and the orogen are very different. The foreland basin typically shows a thermal and rheological structure similar to a rifted continental margin with three brittle layers above three ductile layers. The temperature underneath the orogen is much higher and thus greatly weakens the lithosphere. According to Zhou et al. (2003),[ page needed ] "under compressional stress the lithosphere beneath the mountain range becomes ductile almost entirely, except a thin (about 6 km in the center) brittle layer near the surface and perhaps a thin brittle layer in the uppermost mantle." This lithospheric weakening underneath the orogenic belt may in part cause the regional lithospheric flexure behavior.

Thermal history

Foreland basins are considered to be hypothermal basins (cooler than normal), with low geothermal gradient and heat flow. Heat flow values average between 1 and 2 HFU (40–90 mWm−2. [2] [ page needed ] Rapid subsidence may be responsible for these low values.

Over time sedimentary layers become buried and lose porosity. This can be due to sediment compaction or the physical or chemical changes, such as pressure or cementation. Thermal maturation of sediments is a factor of temperature and time and occurs at shallower depths due to past heat redistribution of migrating brines.

Vitrinite reflectance, which typically demonstrates an exponential evolution of organic matter as a function of time, is the best organic indicator for thermal maturation. Studies have shown that present day thermal measurements of heat flow and geothermal gradients closely correspond to a regime's tectonic origin and development as well as the lithospheric mechanics. [2] [ page needed ]

Fluid migration

Migrating fluids originate from the sediments of the foreland basin and migrate in response to deformation. As a result, brine can migrate over great distances. Evidence of long-range migration includes: 1) correlation of petroleum to distant source rocks, 2) ore bodies deposited from metal-bearing brines, 3) anomalous thermal histories for shallow sediments, 4) regional potassium metasomatism and 5) epigenetic dolomite cements in ore bodies and deep aquifers. [4]

Fluid source

Fluids carrying heat, minerals, and petroleum, have a vast impact on the tectonic regime within the foreland basin. Before deformation, sediment layers are porous and full of fluids, such as water and hydrated minerals. Once these sediments are buried and compacted, the pores become smaller and some of the fluids, about 1/3, leave the pores. This fluid has to go somewhere. Within the foreland basin, these fluids potentially can heat and mineralize materials, as well as mix with the local hydrostatic head.

Major driving force for fluid migration

Orogen topography is the major driving force of fluid migration. The heat from the lower crust moves via conduction and groundwater advection. Local hydrothermal areas occur when deep fluid flow moves very quickly. This can also explain very high temperatures at shallow depths.

Other minor constraints include tectonic compression, thrusting, and sediment compaction. These are considered minor because they are limited by the slow rates of tectonic deformation, lithology and depositional rates, on the order of 0–10 cm yr−1, but more likely closer to 1 or less than 1 cm yr−1. Overpressured zones might allow for faster migration, when 1 kilometer or more of shaley sediments accumulate per 1 million years. [4]

Bethke & Marshak (1990) state that "groundwater that recharges at high elevation migrates through the subsurface in response to its high potential energy toward areas where the water table is lower."

Hydrocarbon migration

Bethke & Marshak (1990) explain that petroleum migrates not only in response to the hydrodynamic forces that drive groundwater flow, but to the buoyancy and capillary effects of the petroleum moving through microscopic pores. Migration patterns flow away from the orogenic belt and into the cratonic interior. Frequently, natural gas is found closer to the orogen and oil is found further away. [5]

Modern (Cenozoic) foreland basin systems

Asia

Middle East

  • Persian Gulf
    • Foreland to the west of the Zagros mountains
    • Underfilled stage
    • Terrestrial part of the basin covers parts of Iraq and Kuwait

Europe

North America

South America

Ancient foreland basin systems

Asia

Europe

North America

South America

See also

Related Research Articles

<span class="mw-page-title-main">Orogeny</span> The formation of mountain ranges

Orogeny is a mountain-building process that takes place at a convergent plate margin when plate motion compresses the margin. An orogenic belt or orogen develops as the compressed plate crumples and is uplifted to form one or more mountain ranges. This involves a series of geological processes collectively called orogenesis. These include both structural deformation of existing continental crust and the creation of new continental crust through volcanism. Magma rising in the orogen carries less dense material upwards while leaving more dense material behind, resulting in compositional differentiation of Earth's lithosphere. A synorogenic process or event is one that occurs during an orogeny.

<span class="mw-page-title-main">Geology of the Alps</span> The formation and structure of the European Alps

The Alps form part of a Cenozoic orogenic belt of mountain chains, called the Alpide belt, that stretches through southern Europe and Asia from the Atlantic all the way to the Himalayas. This belt of mountain chains was formed during the Alpine orogeny. A gap in these mountain chains in central Europe separates the Alps from the Carpathians to the east. Orogeny took place continuously and tectonic subsidence has produced the gaps in between.

<span class="mw-page-title-main">Acadian orogeny</span> North American orogeny

The Acadian orogeny is a long-lasting mountain building event which began in the Middle Devonian, reaching a climax in the early Late Devonian. It was active for approximately 50 million years, beginning roughly around 375 million years ago, with deformational, plutonic, and metamorphic events extending into the Early Mississippian. The Acadian orogeny is the third of the four orogenies that formed the Appalachian orogen and subsequent basin. The preceding orogenies consisted of the Potomac and Taconic orogeny, which followed a rift/drift stage in the Late Neoproterozoic. The Acadian orogeny involved the collision of a series of Avalonian continental fragments with the Laurasian continent. Geographically, the Acadian orogeny extended from the Canadian Maritime provinces migrating in a southwesterly direction toward Alabama. However, the Northern Appalachian region, from New England northeastward into Gaspé region of Canada, was the most greatly affected region by the collision.

<span class="mw-page-title-main">Grenville orogeny</span> Mesoproterozoic mountain-building event

The Grenville orogeny was a long-lived Mesoproterozoic mountain-building event associated with the assembly of the supercontinent Rodinia. Its record is a prominent orogenic belt which spans a significant portion of the North American continent, from Labrador to Mexico, as well as to Scotland.

<span class="mw-page-title-main">Sevier orogeny</span> Mountain-building episode in North America

The Sevier orogeny was a mountain-building event that affected western North America from northern Canada to the north to Mexico to the south.

The Lewis Overthrust is a geologic thrust fault structure of the Rocky Mountains found within the bordering national parks of Glacier in Montana, United States and Waterton Lakes in Alberta, Canada. The structure was created due to the collision of tectonic plates about 59-75 million years ago that drove a several mile thick wedge of Precambrian rock 50 mi (80 km) eastwards, causing it to overlie softer Cretaceous age rock that is 1300 to 1400 million years younger.

<span class="mw-page-title-main">Molasse basin</span> Foreland basin north of the Alps

The Molasse basin is a foreland basin north of the Alps which formed during the Oligocene and Miocene epochs. The basin formed as a result of the flexure of the European plate under the weight of the orogenic wedge of the Alps that was forming to the south.

The Alice Springs Orogeny was a major intraplate tectonic episode in central Australia responsible for the formation of a series of large mountain ranges. The deformation associated with the Alice Spring Orogeny caused the vertically-tilted sandstone layers of the iconic Uluru/Ayers Rock.

<span class="mw-page-title-main">Forebulge</span>

In geology, a forebulge is a flexural bulge in front as a result of a load on the lithosphere, often caused by tectonic interactions and glaciations. An example of forebulge can be seen in the Himalayan foreland basin, a result of the Indian-Eurasian (continent-continent) plate collision, in which the Indian plate subducted and the Eurasian plate created a large load on the lithosphere, leading to the Himalayas and the Ganges foreland basin.

<span class="mw-page-title-main">Rhenohercynian Zone</span> Fold belt of west and central Europe, formed during the Hercynian orogeny

The Rhenohercynian Zone or Rheno-Hercynian zone in structural geology describes a fold belt of west and central Europe, formed during the Hercynian orogeny. The zone consists of folded and thrust Devonian and early Carboniferous sedimentary rocks that were deposited in a back-arc basin along the southern margin of the then existing paleocontinent Laurussia.

<span class="mw-page-title-main">Peter Ziegler</span> Swiss geologist

Peter Alfred Ziegler was a Swiss geologist, who made contributions to the understanding of the geological evolution of Europe and the North Atlantic borderlands, of intraplate tectonics and of plate tectonic controls on the evolution and hydrocarbon potential of sedimentary basins. Ziegler's career consists of 33 years as exploration geologist with the petroleum industry, 30 of which with Shell, and 20 years of university teaching and research.

<span class="mw-page-title-main">Geology of the Western Carpathians</span>

The Western Carpathians are an arc-shaped mountain range, the northern branch of the Alpine-Himalayan fold and thrust system called the Alpide belt, which evolved during the Alpine orogeny. In particular, their pre-Cenozoic evolution is very similar to that of the Eastern Alps, and they constitute a transition between the Eastern Alps and the Eastern Carpathians.

<span class="mw-page-title-main">Andean orogeny</span> Ongoing mountain-forming process in South America

The Andean orogeny is an ongoing process of orogeny that began in the Early Jurassic and is responsible for the rise of the Andes mountains. The orogeny is driven by a reactivation of a long-lived subduction system along the western margin of South America. On a continental scale the Cretaceous and Oligocene were periods of re-arrangements in the orogeny. The details of the orogeny vary depending on the segment and the geological period considered.

<span class="mw-page-title-main">Geology of Russia</span> Overview of the geology of Russia

Tectonic subsidence is the sinking of the Earth's crust on a large scale, relative to crustal-scale features or the geoid. The movement of crustal plates and accommodation spaces produced by faulting brought about subsidence on a large scale in a variety of environments, including passive margins, aulacogens, fore-arc basins, foreland basins, intercontinental basins and pull-apart basins. Three mechanisms are common in the tectonic environments in which subsidence occurs: extension, cooling and loading.

<span class="mw-page-title-main">Tectonics of the Tian Shan</span>

The Tian Shan is a mountain range in central Asia that extends through western China, Kazakhstan, and Kyrgyzstan. The Tian Shan is 2,800 kilometres (1,700 mi) long, and up to 7,400 metres (24,300 ft) high. Throughout the Tian Shan there are several intermontane basins separated by high ranges. Plate tectonic theory makes the assumption that deformation is concentrated along plate boundaries. However, active deformation is observed in the Tian Shan, far from plate boundaries. This apparent contradiction of plate tectonic theory makes the Tian Shan a key place to study the dynamics of intracontinental deformation.

<span class="mw-page-title-main">Carpathian Flysch Belt</span> Tectonic zone in the Carpathian Mountains

The Carpathian Flysch Belt is an arcuate tectonic zone included in the megastructural elevation of the Carpathians on the external periphery of the mountain chain. Geomorphologically it is a portion of the Outer Carpathians. Geologically it is a thin-skinned thrust belt or accretionary wedge, formed by rootless nappes consisting of so-called flysch – alternating marine deposits of claystones, shales and sandstones which were detached from their substratum and moved tens of kilometers to the north (generally). The Flysch Belt is together with Neogene volcanic complexes the only extant tectonic zone along the whole Carpathian arc.

<span class="mw-page-title-main">Himalayan foreland basin</span> Active collisional foreland basin in South Asia

The Himalayan foreland basin is an active collisional foreland basin system in South Asia. Uplift and loading of the Eurasian Plate on to the Indian Plate resulted in the flexure (bending) of the Indian Plate, and the creation of a depression adjacent to the Himalayan mountain belt. This depression was filled with sediment eroded from the Himalaya, that lithified and produced a sedimentary basin ~3 to >7 km deep. The foreland basin spans approximately 2,000 kilometres (1,200 mi) in length and 450 kilometres (280 mi) in width. From west to east the foreland basin stretches across five countries: Pakistan, India, Nepal, Bangladesh, and Bhutan.

The geology of Sicily records the collision of the Eurasian and the African plates during westward-dipping subduction of the African slab since late Oligocene. Major tectonic units are the Hyblean foreland, the Gela foredeep, the Apenninic-Maghrebian orogen, and the Calabrian Arc. The orogen represents a fold-thrust belt that folds Mesozoic carbonates, while a major volcanic unit is found in an eastern portion of the island. The collision of Africa and Eurasia is a retreating subduction system, such that the descending Africa is falling away from Eurasia, and Eurasia extends and fills the space as the African plate falls into the mantle, resulting in volcanic activity in Sicily and the formation of Tyrrhenian slab to the north.

<span class="mw-page-title-main">Junggar Basin</span> Sedimentary basin in Xinjiang, China

The Junggar Basin, also known as the Dzungarian Basin or Zungarian Basin, is one of the largest sedimentary basins in Northwest China. It is located in Dzungaria in northern 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.

References

Citations

  1. Allen et al. 2004
  2. 1 2 3 4 Allen & Allen 2005
  3. Flemings & Jordan 1989
  4. 1 2 Bethke & Marshak 1990
  5. Oliver 1986
  6. 1 2 Fantoni, R.; Franciosi, R. (December 2010). "Tectono-sedimentary setting of the Po Plain and Adriatic Foreland". Rendiconti Lincei Scienze Fisiche e Naturali. 21: 197–209. doi:10.1007/s12210-010-0102-4. S2CID   129249313.
  7. Turrini, C.; Toscani, G; Lacombe, O.; Roure, F. (November 2016). "Influence of structural inheritance on foreland-foredeep system evolution: An example from the Po valley region (northern Italy)". Marine and Petroleum Geology. 77: 376–398. doi:10.1016/j.marpetgeo.2016.06.022.
  8. Mancin, N.; Barbieri, C.; Ventura, M.; Catellani, D.; Di Giulio, A. (2005). "Paleobathymetric evolution of the Venetian-Friuli foreland basin (NE Italy): consequences on flexural modelling and relative rate of tectonic vs. sedimentary processes". Geophysical Research Abstracts. European Geosciences Union. 7 (6759).
  9. 1 2 Pola, M.; Ricciato, A.; Fantoni, R.; Fabbri, P.; Zampieri, D. (June 2014). "Architecture of the western margin of the North Adriatic foreland: The Schio-Vicenza fault system". Italian Journal of Geosciences. 133 (2): 223–234. doi:10.3301/IJG.2014.04.
  10. Adriatic Basin (New Update 2020), Basin reports,
  11. de Alteriis, G. (30 December 1995). "Different foreland basins in Italy: examples from the central and southern Adriatic Sea". Tectonophysics. 252 (1–4): 349–373. doi:10.1016/0040-1951(95)00155-7.
  12. Amadori, C.; Toscani, G.; Di Giulio, A.; Maesano, F.E.; D'Ambrogi, C.; Ghielmi, M.; Fantoni, R. (October 2019). "From cylindrical to non-cylindrical foreland basin: Pliocene–Pleistocene evolution of the Po Plain–Northern Adriatic basin (Italy)". Basin Research. 31 (5): 991–1015. doi: 10.1111/bre.12369 . S2CID   155642258.
  13. Oszczypko, N.; Krzywiec, P.; Popadyuk, I.; Peryt, T. (2006). "The Carpathians and Their Foreland: Geology and Hydrocarbon Resources". In Golonka, J.; Picha, F.J. (eds.). Carpathian Foredeep Basin (Poland and Ukraine): Its Sedimentary, Structural, and Geodynamic Evolution. American Association of Petroleum Geologists. doi:10.1306/985612M843072.
  14. de Leeuwu, A.; Vincent, S; Matoshko, Anton; Matoshko, Andrei; Stoica, Marius; Nicoara, I. (4–8 May 2020). Geodynamic evolution of the East Carpathian Foreland Basin since the Middle Miocene: Implications for sediment supply to the Black Sea and Dacian Basin. EGU General Assembly 2020. doi: 10.5194/egusphere-egu2020-20638 .
  15. Jipa, D. C.; Olariu, C. (2009). Dacian Basin Depositional Architecture and Sedimentary History of a Paratethys Sea (PDF). National Institute of Marine Geology and Geo-Ecology (GeoEcoMar). ISBN   978-973-0-07021-7.
  16. Garcia-Castellanos, D., M. Fernàndez & M. Torné, 2002. Modelling the evolution of the Guadalquivir foreland basin (South Spain). Tectonics 21(3), doi : 10.1029/2002JB002073.

General and cited references

Further reading