Thrombolite: Difference between revisions
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[[Image:PurbeckFormationPortland.jpg|thumb|[[Jurassic]] thrombolite formed around a tree trunk; [[Purbeck Marble|Purbeck Formation]], [[Isle of Portland]], [[Dorset]], [[England]].|400x400px]] |
[[Image:PurbeckFormationPortland.jpg|thumb|[[Jurassic]] thrombolite formed around a tree trunk; [[Purbeck Marble|Purbeck Formation]], [[Isle of Portland]], [[Dorset]], [[England]].|400x400px]] |
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[[File:Fossil Thrombolites at Lake Walyungup, April 2020 02.jpg|thumb|Fossil Thrombolites at Lake Walyungup|400x400px]] |
[[File:Fossil Thrombolites at Lake Walyungup, April 2020 02.jpg|thumb|Fossil Thrombolites at Lake Walyungup|400x400px]] |
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'''Thrombolites''' (from [[Ancient Greek]] |
'''Thrombolites''' (from [[Ancient Greek]] θρόμβος ''thrómbos'' meaning "[[clot]]" and λῐ́θος ''líthos'' meaning "[[Rock (geology)|stone]]") are clotted accretionary [[Structure|structures]] formed in shallow water by the trapping, binding, and cementation of sedimentary grains by [[Biofilm|biofilms]] of [[Microorganism|microorganisms]], especially [[cyanobacteria]].<ref name=":0">{{Cite journal|last=Kennard|first=John M.|last2=James|first2=Noel P.|date=1986|title=Thrombolites and Stromatolites: Two Distinct Types of Microbial Structures|url=https://pubs.geoscienceworld.org/palaios/article/1/5/492-503/114245|journal=PALAIOS|volume=1|issue=5|pages=492|doi=10.2307/3514631}}</ref> |
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== |
== Structures == |
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Thrombolites have a clotted structure |
Thrombolites have a clotted structure without the laminae of stromatolites. Each clot within a thrombolite mound is a separate [[Cyanobacteria|cyanobacterial]] [[Colony (biology)|colony]]. The clots are on the scale of millimetres to centimetres and may be interspersed with [[sand]], [[mud]] or [[Carbonate rock|sparry carbonate]].<ref name=":0" /> Clots that make up thrombolites are called thromboids to avoid confusion with other clotted textures.<ref name=":1">{{Cite journal|last=SHAPIRO|first=R. S.|date=2000|title=A Comment on the Systematic Confusion of Thrombolites|url=|journal=PALAIOS|volume=15|issue=2|pages=166–169|doi=10.1669/0883-1351(2000)015;2|issn=0883-1351}}</ref> The larger clots make up more than 40% of a thrombolite's volume and each clot has a complex internal structure of [[Cell (biology)|cells]] and rimmed lobes resulting primarily from [[calcification]] of the cyanobacterial colony. Very little sediment is found within the clots because the main growth method is calcification rather than sediment trapping.<ref name=":0" /> There is active debate about the size of thromboids, with some seeing thromboids as a macrostructural feature (domical hemispheroid) and others viewing thromboids as a mesostructural feature (random polylobate and subspherical mesoclots).<ref name=":1" /> |
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== Types == |
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There are two main types of thrombolites:<ref name=":2">{{Citation|last=Riding|first=Robert|title=Microbialites, Stromatolites, and Thrombolites|date=2011|url=http://link.springer.com/10.1007/978-1-4020-9212-1_196|work=Encyclopedia of Geobiology|pages=635–654|editor-last=Reitner|editor-first=Joachim|place=Dordrecht|publisher=Springer Netherlands|doi=10.1007/978-1-4020-9212-1_196|isbn=978-1-4020-9211-4|access-date=2021-04-16|editor2-last=Thiel|editor2-first=Volker}}</ref> |
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{{reflist}} |
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=== Calcified microbe thrombolites === |
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This type of thrombolites contain clots that are dominantly composed of [[Calcification|calcified]] [[Micropaleontology|microfossil]] components. These clots do not have a fixed form or size and can expand vertically. Furthermore, [[burrows]] and [[Trilobite|trilobite fragments]] can exist in these thrombolites. They can be found in sedimentary rocks formed in the [[Shallow water marine environment|shallow water]] [[ocean]] during the [[Neoproterozoic]] and early [[Paleozoic|Palaeozoic]].<ref name=":2" /> |
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=== Coarse agglutinated thrombolites === |
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This type of thrombolites are composed of small openings that trapped [[fine-grained]] [[Sediment|sediments]]. Coarse-agglutinated thrombolites can be called "thrombolitic-stromatolites" due to their close relation with the same composition of stromatolites. Because of the ability to trap sediment, the formation of [[coarse]] agglutinated thrombolites directly links to the rise of [[Algae|algal]]-cyanobacterial mats.<ref name=":2" /> |
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== Differences from Stromatolites == |
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Thrombolites can be distinguished from [[Microbialite|microbialites]] or stromatolites by their massive size, which is characterized by macroscopic clotted fabric. [[Stromatolite|Stromatolites]] are similar but consist of layered [[Accretion (geology)|accretions]]. Thrombolites appear with random patterns that can be seen by the naked eye, while stromatolites has the texture of built up layers.<ref name=":1" /> |
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== Ancient Fossil Record == |
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Thrombolites is a type of microbialites, which represents for the formation of life in the early Earth's history by the abundance of cyanobacteria colony existed in each microbialite.<ref name=":3">{{Cite journal|last=Warden|first=John G.|last2=Coshell|first2=Lee|last3=Rosen|first3=Michael R.|last4=Breecker|first4=Daniel O.|last5=Ruthrof|first5=Katinka X.|last6=Omelon|first6=Christopher R.|date=2019|title=The importance of groundwater flow to the formation of modern thrombolitic microbialites|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/gbi.12344|journal=Geobiology|language=en|volume=17|issue=5|pages=536–550|doi=10.1111/gbi.12344|issn=1472-4677}}</ref> Therefore, thrombolites are thought to have contributed to the increase in [[Oxygen cycle|oxygen]] in the early [[Atmosphere of Earth|Earth's atmosphere]]. Nowadays, thrombolites are rare, but still exist in areas of groundwater discharge with high concentration of nutrients and organic ions, such as shallow seawater, freshwater, and saltwater lakes, and streams; nevertheless, there is no evidence of the relationship between groundwater discharge and thrombolites formation.<ref name=":3" /> |
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== Locations == |
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Thrombolites are now only found in a few places in the world, including:<ref name=":3" /> |
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* [[Lake Clifton, Western Australia]] |
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* Lakes Nuoertu and Huhejaran, [[China]] |
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* Basin Lakes and [[Blue Lake (South Australia)|Blue Lake]], [[Australia]] |
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* Ciocaia, [[Romania]] |
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* [[Lake Van]] and [[Lake Salda|Salda Lake]], [[Turkey]] |
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* [[Cuatro Ciénegas]] and Lake Alchichica, [[Mexico]] |
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* Green Lake, USA |
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* Manito Lake and [[Pavilion Lake]], [[Canada]] |
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* [[Laguna Negra]], Argentina |
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* [[Kiritimati|Kiritimati Atoll]], Kiribati |
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== References == |
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==External links== |
==External links== |
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Revision as of 23:33, 16 April 2021
Thrombolites (from Ancient Greek θρόμβος thrómbos meaning "clot" and λῐ́θος líthos meaning "stone") are clotted accretionary structures formed in shallow water by the trapping, binding, and cementation of sedimentary grains by biofilms of microorganisms, especially cyanobacteria.[1]
Structures
Thrombolites have a clotted structure without the laminae of stromatolites. Each clot within a thrombolite mound is a separate cyanobacterial colony. The clots are on the scale of millimetres to centimetres and may be interspersed with sand, mud or sparry carbonate.[1] Clots that make up thrombolites are called thromboids to avoid confusion with other clotted textures.[2] The larger clots make up more than 40% of a thrombolite's volume and each clot has a complex internal structure of cells and rimmed lobes resulting primarily from calcification of the cyanobacterial colony. Very little sediment is found within the clots because the main growth method is calcification rather than sediment trapping.[1] There is active debate about the size of thromboids, with some seeing thromboids as a macrostructural feature (domical hemispheroid) and others viewing thromboids as a mesostructural feature (random polylobate and subspherical mesoclots).[2]
Types
There are two main types of thrombolites:[3]
Calcified microbe thrombolites
This type of thrombolites contain clots that are dominantly composed of calcified microfossil components. These clots do not have a fixed form or size and can expand vertically. Furthermore, burrows and trilobite fragments can exist in these thrombolites. They can be found in sedimentary rocks formed in the shallow water ocean during the Neoproterozoic and early Palaeozoic.[3]
Coarse agglutinated thrombolites
This type of thrombolites are composed of small openings that trapped fine-grained sediments. Coarse-agglutinated thrombolites can be called "thrombolitic-stromatolites" due to their close relation with the same composition of stromatolites. Because of the ability to trap sediment, the formation of coarse agglutinated thrombolites directly links to the rise of algal-cyanobacterial mats.[3]
Differences from Stromatolites
Thrombolites can be distinguished from microbialites or stromatolites by their massive size, which is characterized by macroscopic clotted fabric. Stromatolites are similar but consist of layered accretions. Thrombolites appear with random patterns that can be seen by the naked eye, while stromatolites has the texture of built up layers.[2]
Ancient Fossil Record
Thrombolites is a type of microbialites, which represents for the formation of life in the early Earth's history by the abundance of cyanobacteria colony existed in each microbialite.[4] Therefore, thrombolites are thought to have contributed to the increase in oxygen in the early Earth's atmosphere. Nowadays, thrombolites are rare, but still exist in areas of groundwater discharge with high concentration of nutrients and organic ions, such as shallow seawater, freshwater, and saltwater lakes, and streams; nevertheless, there is no evidence of the relationship between groundwater discharge and thrombolites formation.[4]
Locations
Thrombolites are now only found in a few places in the world, including:[4]
- Lake Clifton, Western Australia
- Lakes Nuoertu and Huhejaran, China
- Basin Lakes and Blue Lake, Australia
- Ciocaia, Romania
- Lake Van and Salda Lake, Turkey
- Cuatro Ciénegas and Lake Alchichica, Mexico
- Green Lake, USA
- Manito Lake and Pavilion Lake, Canada
- Laguna Negra, Argentina
- Kiritimati Atoll, Kiribati
References
External links
- ^ a b c Kennard, John M.; James, Noel P. (1986). "Thrombolites and Stromatolites: Two Distinct Types of Microbial Structures". PALAIOS. 1 (5): 492. doi:10.2307/3514631.
- ^ a b c SHAPIRO, R. S. (2000). "A Comment on the Systematic Confusion of Thrombolites". PALAIOS. 15 (2): 166–169. doi:10.1669/0883-1351(2000)015;2. ISSN 0883-1351.
- ^ a b c Riding, Robert (2011), Reitner, Joachim; Thiel, Volker (eds.), "Microbialites, Stromatolites, and Thrombolites", Encyclopedia of Geobiology, Dordrecht: Springer Netherlands, pp. 635–654, doi:10.1007/978-1-4020-9212-1_196, ISBN 978-1-4020-9211-4, retrieved 2021-04-16
- ^ a b c Warden, John G.; Coshell, Lee; Rosen, Michael R.; Breecker, Daniel O.; Ruthrof, Katinka X.; Omelon, Christopher R. (2019). "The importance of groundwater flow to the formation of modern thrombolitic microbialites". Geobiology. 17 (5): 536–550. doi:10.1111/gbi.12344. ISSN 1472-4677.