It is also believed to be closely connected with the Paraná and Etendeka flood basalt provinces, which formed over the hotspot during the opening of the South Atlantic Ocean.[2]
The Tristan and Gough hotspots are widely spaced end-members of the volcanic system that generated the Walvis Ridge on the African plate and the Rio Grande Rise on the South American plate beginning at 129 to 133 Ma when the Paraná and Etendeka traps formed. Whether or not Tristan and Gough represent two distinct volcanic centers is still debated.[3]
Fairhead & Wilson 2005 argued that the Walvis Ridge is not the product of a deep mantle plume or the Tristan hotspot, but that changes in the internal stress in the spreading African and South American plates trigger changes in the magmatic processes in the Mid-Atlantic Ridge. The Walvis Ridge should then have developed as a result of these periodic stress releases along the Mid-Atlantic Ridge.[4]
O'Connor et al. 2012 found that the hotspot trails in the eastern South Atlantic (Tristan, Gough, Discovery, Shona, and possibly Bouvet) started forming synchronously 44 to 41 Ma. Older seamounts east of these hotspot trails formed at the edge of the African swell where the oceanic crust was spreading apart and are not the product of hotspot volcanism. The Tristan-Gough trail switched from forming a series of aseismic ridges to a broader line of guyots and smaller volcanic ridges at about the same time.[5]
The hotspots of the eastern South Atlantic formed along the plume generation zones of the African large low seismic velocity province (LLSVP). LLSVPs are dense and stable structures, and most of the plumes, kimberlites, and large igneous provinces (LIPs) on Earth can be rotated back to the plume generation zones. All major African LIPs (Karoo, Paraná-Etendeka, and Agulhas) formed at the plume generation zones of the African LLSVP but 132 to 100 Ma the Tristan-Gough hotspot was the only hotspot located at a spreading boundary and therefore the only African hotspot that started to form a volcanic trail.[5]
Palaeoclimatic and evolutionary roleedit
Based on molecular estimates, Arnason et al. 2000 found that the Homo–Pan divergence occurred 13 to 10.5 Ma (in contrast to earlier estimates that suggested around 5 Ma).[6] Arnason et al. also estimated the Platyrrhini–Catarrhini divergence to have occurred around 70 Ma and found that the latter evolved in South America before their dispersal into Africa. Arnason et al. hypothesised that the Rio Grande–Walvis Ridge system was exposed above sea level and formed a chain of islands across the South Atlantic during the Maastrichtian and Palaeocene70 to 65 Ma allowing the primates to disperse across the ocean.[7] Other researchers dismiss the hypothesis of Arnason et al. instead favouring a less spectacular rafting event.[8]
Other hints of transoceanic island hopping in the fossil record is Lavocatavis, a flightless terror bird found in Eocene layers in Algeria, the only one found outside South America.[9]
Arnason, U.; Gullberg, A.; Schweizer Burgete, A.; Janke, A. (2000). "Molecular estimates of primate divergence and new hypotheses for primate dispersal and the origin of modern humans". Hereditas. 133 (3): 217–228. doi:10.1111/j.1601-5223.2000.00217.x. PMID 11433966.
Fairhead, J. D.; Wilson, M. (2005). "Plate tectonic processes in the South Atlantic Ocean: Do we need deep mantle plumes?". In Foulger, G. R. (ed.). Plates, Plumes, and Paradigms, Issue 388. Geological Society of America. pp. 537–554. ISBN9780813723884. Retrieved 2015-05-01.
Mohriak, W. U.; Rosendahl, B. R.; Turner, J. P.; Valente, S. C. (2002). "Crustal architecture of South Atlantic volcanic margins". In Menzies, M. A.; Klemperer, S. L.; Ebinger, C. J.; et al. (eds.). Volcanic Rifted Margins. Vol. 362. Geological Society of America Special Paper. pp. 159–202. doi:10.1130/0-8137-2362-0.159. ISBN9780813723624.
Mourer-Chauviré, C.; Tabuce, R.; Mahboubi, M.; Adaci, M.; Bensalah, M. (2011). "A Phororhacoid bird from the Eocene of Africa". Naturwissenschaften. 98 (10): 815–823. Bibcode:2011NW.....98..815M. doi:10.1007/s00114-011-0829-5. PMID 21874523. S2CID 19805809.
O'Connor, J. M.; Jokat, W.; le Roex, A. P.; Class, C.; Wijbrans, J. R.; Keßling, S.; Kuiper, K. F.; Nebel, O. N. (2012). "Hotspot trails in the South Atlantic controlled by plume and plate tectonic processes". Nature Geoscience. 5 (10): 735–738. Bibcode:2012NatGe...5..735O. doi:10.1038/ngeo1583. Retrieved 2015-05-01.
O'Neill, C.; Müller, R. D.; Steinberger, B. (2005). "On the uncertainties in hot spot reconstructions and the significance of moving hot spot reference frames". Geochemistry, Geophysics, Geosystems. 6 (4): Q04003. Bibcode:2005GGG.....6.4003O. doi:10.1029/2004GC000784.
Poux, C.; Chevret, P.; Huchon, D.; De Jong, W. W.; Douzery, E. J. (2006). "Arrival and diversification of caviomorph rodents and platyrrhine primates in South America". Systematic Biology. 55 (2): 228–244. doi:10.1080/10635150500481390. PMID 16551580. Retrieved 2015-05-01.
tristan, hotspot, volcanic, hotspot, which, responsible, volcanic, activity, which, forms, volcanoes, southern, atlantic, ocean, thought, have, formed, island, tristan, cunha, walvis, ridge, african, plate, marked, this, hotspots, contents, geology, palaeoclim. The Tristan hotspot is a volcanic hotspot which is responsible for the volcanic activity which forms the volcanoes in the southern Atlantic Ocean It is thought to have formed the island of Tristan da Cunha and the Walvis Ridge on the African Plate 1 The Tristan hotspot is marked 42 on this map of hotspots Contents 1 Geology 2 Palaeoclimatic and evolutionary role 3 References 3 1 Notes 3 2 SourcesGeology editIt is also believed to be closely connected with the Parana and Etendeka flood basalt provinces which formed over the hotspot during the opening of the South Atlantic Ocean 2 The Tristan and Gough hotspots are widely spaced end members of the volcanic system that generated the Walvis Ridge on the African plate and the Rio Grande Rise on the South American plate beginning at 129 to 133 Ma when the Parana and Etendeka traps formed Whether or not Tristan and Gough represent two distinct volcanic centers is still debated 3 Fairhead amp Wilson 2005 argued that the Walvis Ridge is not the product of a deep mantle plume or the Tristan hotspot but that changes in the internal stress in the spreading African and South American plates trigger changes in the magmatic processes in the Mid Atlantic Ridge The Walvis Ridge should then have developed as a result of these periodic stress releases along the Mid Atlantic Ridge 4 O Connor et al 2012 found that the hotspot trails in the eastern South Atlantic Tristan Gough Discovery Shona and possibly Bouvet started forming synchronously 44 to 41 Ma Older seamounts east of these hotspot trails formed at the edge of the African swell where the oceanic crust was spreading apart and are not the product of hotspot volcanism The Tristan Gough trail switched from forming a series of aseismic ridges to a broader line of guyots and smaller volcanic ridges at about the same time 5 The hotspots of the eastern South Atlantic formed along the plume generation zones of the African large low seismic velocity province LLSVP LLSVPs are dense and stable structures and most of the plumes kimberlites and large igneous provinces LIPs on Earth can be rotated back to the plume generation zones All major African LIPs Karoo Parana Etendeka and Agulhas formed at the plume generation zones of the African LLSVP but 132 to 100 Ma the Tristan Gough hotspot was the only hotspot located at a spreading boundary and therefore the only African hotspot that started to form a volcanic trail 5 Palaeoclimatic and evolutionary role editBased on molecular estimates Arnason et al 2000 found that the Homo Pan divergence occurred 13 to 10 5 Ma in contrast to earlier estimates that suggested around 5 Ma 6 Arnason et al also estimated the Platyrrhini Catarrhini divergence to have occurred around 70 Ma and found that the latter evolved in South America before their dispersal into Africa Arnason et al hypothesised that the Rio Grande Walvis Ridge system was exposed above sea level and formed a chain of islands across the South Atlantic during the Maastrichtian and Palaeocene 70 to 65 Ma allowing the primates to disperse across the ocean 7 Other researchers dismiss the hypothesis of Arnason et al instead favouring a less spectacular rafting event 8 Other hints of transoceanic island hopping in the fossil record is Lavocatavis a flightless terror bird found in Eocene layers in Algeria the only one found outside South America 9 References editNotes edit Fairhead amp Wilson 2005 p 539 Mohriak et al 2002 O Neill Muller amp Steinberger 2005 3 1 Tristan de Cunha pp 11 12 Fairhead amp Wilson 2005 Abstract p 537 a b O Connor et al 2012 pp 1 2 Arnason et al 2000 Abstract Arnason et al 2000 p 223 Fig 2 Poux et al 2006 Possible Migration Histories p 240 Mourer Chauvire et al 2011 Abstract Sources edit Arnason U Gullberg A Schweizer Burgete A Janke A 2000 Molecular estimates of primate divergence and new hypotheses for primate dispersal and the origin of modern humans Hereditas 133 3 217 228 doi 10 1111 j 1601 5223 2000 00217 x PMID 11433966 Fairhead J D Wilson M 2005 Plate tectonic processes in the South Atlantic Ocean Do we need deep mantle plumes In Foulger G R ed Plates Plumes and Paradigms Issue 388 Geological Society of America pp 537 554 ISBN 9780813723884 Retrieved 2015 05 01 Mohriak W U Rosendahl B R Turner J P Valente S C 2002 Crustal architecture of South Atlantic volcanic margins In Menzies M A Klemperer S L Ebinger C J et al eds Volcanic Rifted Margins Vol 362 Geological Society of America Special Paper pp 159 202 doi 10 1130 0 8137 2362 0 159 ISBN 9780813723624 Mourer Chauvire C Tabuce R Mahboubi M Adaci M Bensalah M 2011 A Phororhacoid bird from the Eocene of Africa Naturwissenschaften 98 10 815 823 Bibcode 2011NW 98 815M doi 10 1007 s00114 011 0829 5 PMID 21874523 S2CID 19805809 O Connor J M Jokat W le Roex A P Class C Wijbrans J R Kessling S Kuiper K F Nebel O N 2012 Hotspot trails in the South Atlantic controlled by plume and plate tectonic processes Nature Geoscience 5 10 735 738 Bibcode 2012NatGe 5 735O doi 10 1038 ngeo1583 Retrieved 2015 05 01 O Neill C Muller R D Steinberger B 2005 On the uncertainties in hot spot reconstructions and the significance of moving hot spot reference frames Geochemistry Geophysics Geosystems 6 4 Q04003 Bibcode 2005GGG 6 4003O doi 10 1029 2004GC000784 Poux C Chevret P Huchon D De Jong W W Douzery E J 2006 Arrival and diversification of caviomorph rodents and platyrrhine primates in South America Systematic Biology 55 2 228 244 doi 10 1080 10635150500481390 PMID 16551580 Retrieved 2015 05 01 37 S 12 W 37 S 12 W 37 12 Retrieved from https en wikipedia org w index php title Tristan hotspot amp oldid 1187822496, wikipedia, wiki, book, books, library,
