Graben
Ingeology,agraben(/ˈɡrɑːbən/) is adepressedblock of thecrustof a planet or moon, bordered by parallelnormal faults.
Etymology[edit]
Grabenis aloan wordfromGerman,meaning 'ditch' or 'trench'. The first known usage of the word in the geologic context was byEduard Suessin 1883.[1]The plural form is eithergraben[2]orgrabens.[3]
Formation[edit]
A graben is avalleywith a distinctescarpmenton each side caused by the displacement of a block of land downward. Graben often occur side by side withhorsts.Horst and graben structures indicate tensional forces and crustal stretching.
Graben are produced from parallel normal faults, where the displacement of thehanging wallis downward, while that of thefootwallis upward. The faults typically dip toward the center of the graben from both sides. Horsts are parallel blocks that remain between graben; the bounding faults of a horst typically dip away from the center line of the horst. Single or multiple graben can produce arift valley.
Half-graben[edit]
In manyrifts,the graben are asymmetric, with a major fault along only one of the boundaries, and these are known as half-graben. The polarity (throw direction) of the main bounding faults typically alternates along the length of the rift. The asymmetry of a half-graben strongly affects syntectonic deposition. Comparatively littlesedimententers the half-graben across the main bounding fault because of footwall uplift on the drainage systems. The exception is at any major offset in the bounding fault, where a relay ramp may provide an important sediment input point. Most of the sediment will enter the half-graben down the unfaulted hanging wall side (e.g.,Lake Baikal).[4]
Examples[edit]
Africa[edit]
- East African RiftValley
- Lucapa Graben,Lunda Norte Province,Angola
Antarctica[edit]
Asia[edit]
- Narmada RiverValley,central India
- lowerGodavari RiverValley,southern India
- Baikal Rift Zone,Siberia,Russia
- Moma Graben,Sakha Republic,Russia
- Büyük Menderes Graben,Turkey
- Fossa Magna,Honshu,Japan
- Ariake Seaas part of the Unzen graben,Kyushu,Japan
- Beppu–Shimabara graben,Kyushu, Japan
Europe[edit]
- Rhine valley,border area of westGermanyand northeastFrance
- Oslo grabenaroundOslo,Norway
- Central Lowlands,Scotland
- Worcester Basin,England
- Central Graben,North Sea
- Viking Graben, North Sea
- Vättern,Sweden
- Lowtherville Graben,Ventnor,Isle of Wight,England[5][6]
North America[edit]
Canada[edit]
- Ottawa-Bonnechere Graben,Ontarioand Quebec, Canada
- Saguenay Graben,Quebec,Canada
Guatemala[edit]
- Guatemala Cityvalley,Guatemala
United States[edit]
- Basin and Range Provinceof southwesternNorth Americais an example of multiple horst/graben structures, includingDeath Valley,withSalt Lake Valleybeing the easternmost andOwens Valleybeing the westernmost.
- Lake George Basin,New York, U.S.
- Lake Tahoe Basin,CaliforniaandNevada,U.S.
- Republic Graben,Republic,Washington,U.S.
- Rio Grande RiftValley inColorado/New Mexico/Texasof theUnited States
- Rough Creek Graben,Kentucky,U.S.
- Santa Clara Valley,California,U.S.
- WesternSnake River Plain,Idaho,U.S.
- SouthwestSan Bernardino Valley (Arizona),U.S.
Multi-national[edit]
- Eastern North America Rift Basins,Canada and the U.S.
- Midcontinent Rift System,Canada and the U.S.
- Salton Trough,Mexico and the U.S.
Oceania[edit]
- Firth of ThamesofHauraki GulfandHauraki PlainsofHauraki Rift(Hauraki half grabens),North Island,New Zealand[7]
- Tikitere Grabenwithin theTaupō Rift,North Island, New Zealand.[8]
- Gulf St Vincent,South Australia,Australia[9]
- Tamar Valley,Tasmania,Australia[10]
South America[edit]
See also[edit]
- European Cenozoic Rift System
- Fossa (geology)– Long, narrow, shallow depression
Notes[edit]
- ^"graben".Oxford English Dictionary(Online ed.).Oxford University Press.(Subscription orparticipating institution membershiprequired.)
- ^Schlumberger Oilfield Glossary
- ^horst and graben.Encyclopædia Britannica.Retrieved15 November2012.
- ^Hans Nelson, C.; Karabanov, Evgeny B.; Colman, Steven M.; Escutia, Carlota (1999). "Tectonic and sediment supply control of deep rift lake turbidite systems: Lake Baikal, Russia".Geology.27(2): 163–166.Bibcode:1999Geo....27..163N.doi:10.1130/0091-7613(1999)027<0163:TASSCO>2.3.CO;2.
- ^CAREY, JONATHAN (2011).The Progressive Development and Post-failure Behaviour of Deep-seated Landslide Complexes(Doctoral thesis). Durham University.
- ^Carey, Jonathan (November 2014)."Patterns of movement in the Ventnor landslide complex, Isle of Wight, southern England".Landslides.12(6): 1107.Bibcode:2015Lands..12.1107C.doi:10.1007/s10346-014-0538-1.
- ^Hochstein, M.P.; Nixon, I.M. (1979)."Geophysical study of the Hauraki Depression, North Island, New Zealand".New Zealand Journal of Geology and Geophysics.22(1): 1–19.Bibcode:1979NZJGG..22....1H.doi:10.1080/00288306.1979.10422550.
- ^Manville, V.; Hodgson, K. A.; Nairn, I. A. (2007)."A review of break-out floods from volcanogenic lakes in New Zealand".New Zealand Journal of Geology and Geophysics.50(2): 131–150.Bibcode:2007NZJGG..50..131M.doi:10.1080/00288300709509826.S2CID129792354.
- ^Sprigg, R.C. (1961)."The Oil and Gas Prospects of the St. Vincents Gulf Graben".The APPEA Journal.1(1): 71–88.doi:10.1071/AJ60011.
- ^Stacey, A. R., and Berry, R. F., (2004). "The Structural history of Tasmania: a review for petroleum explorers",PESA Eastern Australasian Basins Symposium II
References[edit]
- McKnight, Tom L; Hess, Darrel (2000)."The Internal Processes: Graben".Physical Geography: A Landscape Appreciation.Upper Saddle River, NJ: Prentice Hall. pp.417.ISBN0-13-020263-0.
