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[[File:Distribution of detritus.png|thumb|Distribution of detritus in a depositional system]] |
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'''Abyssal Fans''', also known as '''deep-sea fans''', '''underwater deltas''', and '''submarine fans''', are underwater structures that look like [[river delta|deltas]] formed at the end of many large rivers, such as the [[Nile]] or [[Mississippi River]]s. Abyssal fans are also thought of as an underwater version of [[alluvial fan|alluvial fans]]. |
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{{short description|Underwater geological structures associated with large-scale sediment deposition}} |
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'''Abyssal fans''', also known as '''deep-sea fans''', '''underwater deltas''', and '''submarine fans''', are underwater geological structures associated with large-scale [[sediment deposition]] and formed by [[turbidity current]]s. They can be thought of as an underwater version of [[alluvial fans]] and can vary dramatically in size, with widths from several kilometres to several thousands of kilometres.<ref>Gluyas, J. & Swarbrick, R. (2004) Petroleum Geoscience. Publ. Blackwell Publishing</ref> The largest is the [[Bengal Fan]], followed by the [[Indus River#Geology|Indus Fan]], but major fans are also found at the outlet of the [[Amazon River|Amazon]], [[Congo Deep-Sea Fan|Congo]], [[Mississippi River|Mississippi]] and elsewhere.<ref>{{cite journal | author=Clift | author2=Gaedicke | author3=Edwards | author4=Lee | author5=Hildebrand | author6=Amjad | author7=White | author8=Schlüter | name-list-style=amp | title=The stratigraphic evolution of the Indus Fan and the history of sedimentation in the Arabian Sea | year=2002 | journal=Marine Geophysical Researches | volume=23 | issue=3 | pages=223–245 | doi=10.1023/A:1023627123093 | bibcode=2002MarGR..23..223C | s2cid=129735252 }}</ref><ref>{{cite journal | author=Covault, J.A. | title=Submarine Fans and Canyon-Channel Systems: A Review of Processes, Products, and Models | url=https://www.nature.com/scitable/knowledge/library/submarine-fans-and-canyon-channel-systems-a-24178428 | year=2011 | journal= Nature Education Knowledge | volume=3 | issue=10 | page=4 }}</ref><ref>{{cite journal | author=Shanmugam, G. | title=Submarine fans: A critical retrospective (1950–2015) | year=2016 | journal= Journal of Palaeogeography | volume=5 | issue=2 | pages=110–184 | doi=10.1016/j.jop.2015.08.011 | bibcode=2016JPalG...5..110S | doi-access=free }}</ref> |
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== Formation == |
== Formation == |
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{{unsourced|section|date=December 2022}} |
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Abyssal (or submarine) fans are formed due to [[turbidites]] . Tubidites are essentially gravity driven underwater avalanches. As sediment is deposited on the [[continental slope]] , the steepest part of the ocean, it is prone to sliding down onto the continental rise due to gravity. Once the weight of the sediment accumulating gets to be too much, the pile of sediment will slide down all at once falling down onto the continental rise. After thousands of years of turbidite deposition on the rise, a fan forms towards the top of the continental rise. This fan is similar to an [[alluvial fan]] found on land near mountains and rivers. The abyssal fan has characteristics of a standard turbidite. The Bouma Sequence is used to describe the nature and sediment patterns of a turbidite. |
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Abyssal (or submarine) fans are formed from turbidity currents. |
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These currents begin when a [[Geology|geologic activity]] pushes sediments over the edge of a [[continental shelf]] and down the [[continental slope]], creating an underwater landslide. A dense slurry of [[muds]] and [[sand]]s speeds towards the foot of the slope, until the current slows. The decreasing current, having a reduced ability to transport sediments, deposits the grains it carries, thus creating a submarine fan. The slurry continues to slow as it is moved towards the [[continental rise]] until it reaches the ocean bed. Thus results a series of graded sediments of sand, silt and mud, which are known as [[turbidites]], as described by the [[Bouma sequence]]. |
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== See also == |
== See also == |
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*[[List of landforms#Coastal and oceanic landforms|List of |
*[[List of landforms#Coastal and oceanic landforms|List of oceanic landforms]] |
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==References== |
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{{reflist}} |
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| ⚫ | * {{cite web|url=http://www.bakerhughesdirect.com/cgi/hello.cgi/BHI/public/bakerhughes/resources/indepth/72k/Turbodites.pdf |title=Turbidites Hold Great Potential for Deepwater Exploration |publisher=Baker Hughes, Inc. |year=2000 }}{{dead link|date=June 2017 |bot=InternetArchiveBot |fix-attempted=yes }} |
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| ⚫ | * {{cite web|url=http://vtchl.uiuc.edu/people/parkerg/_private/Preprints/TurbJumpJHR.pdf|title=The Response of Turbidity Currents to a Canyon-Fan Transition: Internal Hydraulic Jumps and Depositional Signatures|year=2004|author=Svetlana Kostic|author2=Gary Parker|access-date=2009-09-17|archive-url=https://web.archive.org/web/20080820112844/http://vtchl.uiuc.edu/people/parkerg/_private/Preprints/TurbJumpJHR.pdf|archive-date=2008-08-20|url-status=dead}} |
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* Allen, Philip & Allen, John, 2005. Basin Analysis: Principles and Applications. 2nd ed. Blackwell. |
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[[Category:Physical oceanography]] |
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[[Category:River deltas| Abyssal fan]] |
[[Category:River deltas| Abyssal fan]] |
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[[Category:Coastal and oceanic landforms]] |
[[Category:Coastal and oceanic landforms]] |
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[[es:Abanico abisal]] |
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Latest revision as of 05:35, 22 June 2023
Abyssal fans, also known as deep-sea fans, underwater deltas, and submarine fans, are underwater geological structures associated with large-scale sediment deposition and formed by turbidity currents. They can be thought of as an underwater version of alluvial fans and can vary dramatically in size, with widths from several kilometres to several thousands of kilometres.[1] The largest is the Bengal Fan, followed by the Indus Fan, but major fans are also found at the outlet of the Amazon, Congo, Mississippi and elsewhere.[2][3][4]
Formation
[edit] |
Abyssal (or submarine) fans are formed from turbidity currents.
These currents begin when a geologic activity pushes sediments over the edge of a continental shelf and down the continental slope, creating an underwater landslide. A dense slurry of muds and sands speeds towards the foot of the slope, until the current slows. The decreasing current, having a reduced ability to transport sediments, deposits the grains it carries, thus creating a submarine fan. The slurry continues to slow as it is moved towards the continental rise until it reaches the ocean bed. Thus results a series of graded sediments of sand, silt and mud, which are known as turbidites, as described by the Bouma sequence.
See also
[edit]References
[edit]- ^ Gluyas, J. & Swarbrick, R. (2004) Petroleum Geoscience. Publ. Blackwell Publishing
- ^ Clift; Gaedicke; Edwards; Lee; Hildebrand; Amjad; White & Schlüter (2002). "The stratigraphic evolution of the Indus Fan and the history of sedimentation in the Arabian Sea". Marine Geophysical Researches. 23 (3): 223–245. Bibcode:2002MarGR..23..223C. doi:10.1023/A:1023627123093. S2CID 129735252.
- ^ Covault, J.A. (2011). "Submarine Fans and Canyon-Channel Systems: A Review of Processes, Products, and Models". Nature Education Knowledge. 3 (10): 4.
- ^ Shanmugam, G. (2016). "Submarine fans: A critical retrospective (1950–2015)". Journal of Palaeogeography. 5 (2): 110–184. Bibcode:2016JPalG...5..110S. doi:10.1016/j.jop.2015.08.011.
Sources
[edit]- "Turbidites Hold Great Potential for Deepwater Exploration" (PDF). Baker Hughes, Inc. 2000.[permanent dead link]
- Svetlana Kostic; Gary Parker (2004). "The Response of Turbidity Currents to a Canyon-Fan Transition: Internal Hydraulic Jumps and Depositional Signatures" (PDF). Archived from the original (PDF) on 2008-08-20. Retrieved 2009-09-17.
- Allen, Philip & Allen, John, 2005. Basin Analysis: Principles and Applications. 2nd ed. Blackwell.
