Content deleted Content added
recat |
Citation bot (talk | contribs) Removed URL that duplicated identifier. | Use this bot. Report bugs. | #UCB_CommandLine |
||
| (676 intermediate revisions by more than 100 users not shown) | |||
Line 1:
{{Short description|Large igneous province in India}}
{{Use Indian English|date=January 2016}}
{{Use dmy dates|date=October 2020}}
[[File:India Geology Zones.jpg|thumb|Geologic map of India, showing the Deccan Traps in blue-purple]]
[[File:Western-Ghats-Matheran.jpg|thumb|right|The [[Western Ghats]] at [[Matheran]] in Maharashtra]]
[[File:Deccan Traps Maharashtra India 22Mar2018 SkySat.jpg|thumb|Oblique satellite view of the Deccan Traps]]
[[File:Deccan traps.png|thumb|upright=1.25|Map of the Deccan Traps<ref name=":2">{{cite journal |last1=Götze |first1=Jens |last2=Hofmann |first2=Beda |last3=Machałowski |first3=Tomasz |last4=Tsurkan |first4=Mikhail V. |last5=Jesionowski |first5=Teofil |last6=Ehrlich |first6=Hermann |last7=Kleeberg |first7=Reinhard |last8=Ottens |first8=Berthold |title=Biosignatures in Subsurface Filamentous Fabrics (SFF) from the Deccan Volcanic Province, India |journal=Minerals |date=16 June 2020 |volume=10 |issue=6 |pages=540 |doi=10.3390/min10060540|bibcode=2020Mine...10..540G |doi-access=free }}</ref>]]
The '''Deccan Traps''' are a [[large igneous province]] of west-central India (17–24°N, 73–74°E). They are one of the largest [[Volcano|volcanic]] features on Earth, taking the form of a large [[shield volcano]].<ref name=":0">{{Cite journal|last=Sen|first=Gautam|date=2001-12-01|title=Generation of Deccan Trap magmas|journal=Journal of Earth System Science|language=en|volume=110|issue=4|pages=409–431|doi=10.1007/BF02702904|bibcode=2001InEPS.110..409S|s2cid=52107268|issn=0973-774X|doi-access=free}}</ref> They consist of many layers of solidified [[flood basalt]] that together are more than about {{convert|2|km||sigfig=2}} thick, cover an area of about {{Convert|500000|km2|sigfig=1}},<ref name="Singh_and_Gupta94">{{cite journal |title=Workshop yields new insight into volcanism at Deccan Traps, India |first1=R. N. |last1=Singh |first2=K. R. |last2=Gupta |journal=Eos |year=1994 |volume=75 |issue= 31 |pages=356 |doi=10.1029/94EO01005 |bibcode=1994EOSTr..75..356S}}</ref> and have a volume of about {{Convert|1000000|km3|sigfig=1}}.<ref name="Dessert2001">{{cite journal |title=Erosion of Deccan Traps determined by river geochemistry: impact on the global climate and the 87Sr/86Sr ratio of seawater |first1=Céline |last1=Dessert |first2=Bernard |last2=Dupréa |first3=Louis M. |last3=Françoisa |first4=Jacques |last4=Schotta |first5=Jérôme |last5=Gaillardet |first6=Govind |last6=Chakrapani |first7=Sujit |last7=Bajpai |journal=Earth and Planetary Science Letters |year=2001 |volume=188 |issue=3–4 |pages=459–474 |doi=10.1016/S0012-821X(01)00317-X |bibcode=2001E&PSL.188..459D}}</ref> Originally, the Deccan Traps may have covered about {{Convert|1500000|km2|sigfig=1}},<ref name="MIT-Chu2014">[https://news.mit.edu/2014/volcanic-eruption-dinosaur-extinction-1211 "What really killed the dinosaurs?"] Jennifer Chu, MIT News Office, 11 December 2014</ref> with a correspondingly larger original volume. This volume overlies the [[Archean]] age [[Indian Shield]], which is likely the [[lithology]] the province passed through during eruption. The province is commonly divided into four subprovinces: the main Deccan, the [[Malwa|Malwa Plateau]], the Mandla Lobe, and the Saurashtran Plateau.<ref name=":1">{{Cite book|last=Macdougall|first=J. D.|title=Continental Flood Basalts|date=1988|publisher=Springer Netherlands|isbn=978-94-015-7805-9|___location=Dordrecht|oclc=851375252}}</ref>
The eruptions occurred over a 600–800,000 year time period between around 66.3 to 65.6 million years ago, spanning the [[Cretaceous–Paleogene boundary]]. While some authors have suggested that the eruptions were the primary cause of the [[Cretaceous–Paleogene extinction event|Cretaceous–Paleogene mass extinction event]], which dates to around 66.05 million years ago,<ref>{{Cite journal |last1=Schoene |first1=Blair |last2=Eddy |first2=Michael P. |last3=Keller |first3=C. Brenhin |last4=Samperton |first4=Kyle M. |date=2021-04-16 |title=An evaluation of Deccan Traps eruption rates using geochronologic data |url=https://gchron.copernicus.org/articles/3/181/2021/ |journal=Geochronology |language=en |volume=3 |issue=1 |pages=181–198 |doi=10.5194/gchron-3-181-2021 |doi-access=free |bibcode=2021GeChr...3..181S |issn=2628-3719}}</ref> this has been strongly disputed, with many authors suggesting that the [[Chicxulub impact]] was the primary cause of the extinction.<ref name=":4">{{Cite journal |last1=Morgan |first1=Joanna V. |last2=Bralower |first2=Timothy J. |last3=Brugger |first3=Julia |last4=Wünnemann |first4=Kai |date=2022-04-12 |title=The Chicxulub impact and its environmental consequences |url=https://www.nature.com/articles/s43017-022-00283-y |journal=Nature Reviews Earth & Environment |language=en |volume=3 |issue=5 |pages=338–354 |doi=10.1038/s43017-022-00283-y |bibcode=2022NRvEE...3..338M |issn=2662-138X|url-access=subscription }}</ref><ref name=":6">{{Citation |last=Smit |first=J. |title=The KPg boundary Chicxulub impact-extinction hypothesis: The winding road towards a solid theory |date=2022-06-21 |work=From the Guajira Desert to the Apennines, and from Mediterranean Microplates to the Mexican Killer Asteroid: Honoring the Career of Walter Alvarez |pages=391–414 |editor-last=Koeberl |editor-first=Christian |url=https://research.vu.nl/ws/portalfiles/portal/222623549/The_KPg_boundary_Chicxulub_impact_extinction_hypothesis.pdf |access-date=2024-08-13 |publisher=Geological Society of America |language=en |doi=10.1130/2022.2557(19) |isbn=978-0-8137-2557-4 |editor2-last=Claeys |editor2-first=Philippe |editor3-last=Montanari |editor3-first=Alessandro}}</ref><ref name=":5">{{Cite journal |last1=Chiarenza |first1=Alfio Alessandro |last2=Farnsworth |first2=Alexander |last3=Mannion |first3=Philip D. |last4=Lunt |first4=Daniel J. |last5=Valdes |first5=Paul J. |last6=Morgan |first6=Joanna V. |last7=Allison |first7=Peter A. |date=2020-07-21 |title=Asteroid impact, not volcanism, caused the end-Cretaceous dinosaur extinction |journal=Proceedings of the National Academy of Sciences |language=en |volume=117 |issue=29 |pages=17084–17093 |doi=10.1073/pnas.2006087117 |doi-access=free |issn=0027-8424 |pmc=7382232 |pmid=32601204}}</ref><ref name=":7">{{Cite journal |last1=O’Connor |first1=Lauren K. |last2=Jerrett |first2=Rhodri M. |last3=Price |first3=Gregory D. |last4=Lyson |first4=Tyler R. |last5=Lengger |first5=Sabine K. |last6=Peterse |first6=Francien |last7=van Dongen |first7=Bart E. |date=2024-12-20 |title=Terrestrial evidence for volcanogenic sulfate-driven cooling event ~30 kyr before the Cretaceous–Paleogene mass extinction |journal=Science Advances |language=en |volume=10 |issue=51 |pages=eado5478 |doi=10.1126/sciadv.ado5478 |issn=2375-2548 |pmc=11654674 |pmid=39693422}}</ref> While some scholars suggest that the eruptions may have been a contributing factor in the extinctions, others suggest that the role of the Deccan Traps in the extinction were negligible or even partially negated the effects of the impact.<ref name=":6" /><ref name=":5" />
The Deccan Traps are thought to have been produced in major part by the still active [[Réunion hotspot]], responsible for the creation of the modern [[Mascarene Islands]] in the Indian Ocean.<ref>{{Cite journal |last1=Glišović |first1=Petar |last2=Forte |first2=Alessandro M. |date=2017-02-10 |title=On the deep-mantle origin of the Deccan Traps |url=https://www.science.org/doi/10.1126/science.aah4390 |journal=Science |language=en |volume=355 |issue=6325 |pages=613–616 |doi=10.1126/science.aah4390 |pmid=28183974 |bibcode=2017Sci...355..613G |issn=0036-8075|url-access=subscription }}</ref>
==Etymology==
The term ''[[Trap rock|trap]]'' has been used in [[geology]] since 1785–1795 for such [[rock formation]]s. It is derived from the Swedish word for stairs ({{lang|sv|trapp}}) and refers to the step-like hills forming the landscape of the region.<ref name=":3">[https://www.dictionary.com/browse/trap Trap] at dictionary.reference.com</ref> The name ''Deccan'' has Sanskrit origins meaning "southern".<ref name=":1" />
==History==
[[File:Ajanta caves 1.JPG|thumb|upright|Deccan Traps at [[Ajanta Caves]]]]
{{see also | Gondwana#Opening_of_western_Indian_Ocean | l1= Gondwana and opening of western Indian Ocean | Geology of India}}
The Deccan Traps began forming 66.25 [[Geologic time scale|million years ago]],<ref name="MIT-Chu2014"/> at the end of the [[Cretaceous]] period, although it is possible that some of the oldest material may underlie younger material.<ref name=":0" /><ref name=":1" /> The bulk of the volcanic eruption occurred at the [[Western Ghats]] between 66 and 65 million years ago when lava began to extrude in [[Fissure vent|fissure eruptions]].<ref>{{Cite book|last=Krishnan|first=M.S. |title=Geology of India and Burma|date=2006|publisher=CBS Publishers and Distributors|isbn=81-239-0012-0|edition=6th |___location=New Delhi|oclc=778055464}}</ref> Determining the exact age for Deccan rock is difficult due to a number of limitations, one being that the transition between eruption events may have lasted only a few thousand years and the resolution of dating methods is not sufficient to pinpoint these events. In this way, determining the rate of magma emplacement is also difficult to constrain.<ref name=":0" /> This series of eruptions may have lasted for less than 30,000 years.<ref>"[https://www.sciencedaily.com/releases/2005/08/050810130729.htm India's Smoking Gun: Dino-killing Eruptions]." ''ScienceDaily,'' 10 August 2005.</ref>
The original area covered by the [[lava flow]]s is estimated to have been as large as {{convert|1.5|e6km2||abbr=unit||}}, approximately half the size of modern [[India]]. The Deccan Traps region was reduced to its current size by [[erosion]] and plate tectonics; the present area of directly observable lava flows is around {{convert|500000|km2|sigfig=1|abbr=on}}.
The Deccan Traps are segmented into three stratigraphic units: the Upper, Middle, and Lower traps. While it was previously interpreted that these groups represented their own key points in the sequence of events in Deccan extrusion, it is now more widely accepted that these horizons relate more closely to paleotopography and distance from the eruption site.<ref name=":1" />
==Effect on mass extinctions and climate==
The release of [[volcanic gas]]es, particularly [[sulfur dioxide]], during the formation of the traps may have contributed to [[Climate variability and change|climate change]]. An average drop in temperature of about {{convert|2|C-change|F-change}} was recorded during this period.<ref>{{cite journal|author=Royer, D. L.|author2=Berner, R. A.|author3=Montañez, I. P.|author4=Tabor, N. J.|author5=Beerling, D. J. |author5-link=David Beerling |year=2004 |title=CO<sub>2</sub> as a primary driver of Phanerozoic climate|journal=GSA Today|volume=14|issue=3|pages=4–10|issn=1052-5173|doi=10.1130/1052-5173(2004)014<4:CAAPDO>2.0.CO;2|doi-access=free|bibcode=2004GSAT...14c...4R }}</ref>
Because of its magnitude, some scientists (notably [[Gerta Keller]]) have speculated that the gases released during the formation of the Deccan Traps played a major role in the [[Cretaceous–Paleogene extinction event|Cretaceous–Paleogene (K–Pg) extinction event]] (also known as the Cretaceous–Tertiary or K–T extinction).<ref>{{cite journal|title= A Volcanic Eruption|last= Courtillot|first= Vincent|date= 1990|journal= Scientific American|doi= 10.1038/scientificamerican1090-85|pmid= 11536474|issue= 4|volume= 263|pages= 85–92|bibcode= 1990SciAm.263d..85C}}</ref> It has been theorized that sudden cooling due to sulfurous volcanic gases released by the formation of the traps and toxic gas emissions may have contributed significantly to the K–Pg mass extinction.<ref>{{cite journal|title= Star-Struck?|last= Beardsley|first= Tim|date= 1988|journal= Scientific American|doi= 10.1038/scientificamerican0488-37b|volume= 258|issue= 4|pages= 37–40|bibcode= 1988SciAm.258d..37B}}</ref> However, the current consensus among the scientific community is that the extinction was primarily triggered by the [[Chicxulub crater|Chicxulub impact event]] in North America, which would have produced a sunlight-blocking dust cloud that killed much of the plant life and reduced global temperature (this cooling is called an [[impact winter]]).<ref name="science">{{cite journal|last=Schulte|first=Peter|date=5 March 2010|title=The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary|journal=Science|volume=327|issue=5970|pages=1214–1218|issn=1095-9203 |doi=10.1126/science.1177265|pmid=20203042|bibcode=2010Sci...327.1214S|s2cid=2659741|display-authors=etal|url=http://doc.rero.ch/record/210367/files/PAL_E4389.pdf |archive-url=https://web.archive.org/web/20170921215225/http://doc.rero.ch/record/210367/files/PAL_E4389.pdf |archive-date=2017-09-21 |url-status=live}}</ref>
A 2014 study suggested the extinction may have been caused by both the volcanism and the impact event.<ref>Keller, G., ''Deccan volcanism, the Chicxulub impact, and the end-Cretaceous mass extinction: Coincidence? Cause and effect?,'' in ''Volcanism, Impacts, and Mass Extinctions: Causes and Effects,'' GSA Special Paper 505, pp. 29–55, 2014 [http://specialpapers.gsapubs.org/content/early/2014/06/10/2014.2505_03.1.abstract abstract] {{Webarchive|url=https://web.archive.org/web/20170618024315/http://specialpapers.gsapubs.org/content/early/2014/06/10/2014.2505_03.1.abstract |date=18 June 2017}}</ref><ref>{{cite journal |last1=Schoene |first1=B. |last2=Samperton |first2=K. M. |last3=Eddy |first3=M. P. |last4=Keller |first4=G. |last5=Adatte |first5=T. |last6=Bowring |first6=S. A. |last7=Khadri |first7=S. F. R. |last8=Gertsch |first8=B. |title=U-Pb geochronology of the Deccan Traps and relation to the end-Cretaceous mass extinction |journal=Science |date=11 December 2014 |volume=347 |issue=6218 |pages=182–184 |doi=10.1126/science.aaa0118 |bibcode=2015Sci...347..182S |pmid=25502315|s2cid=206632431 }}</ref> This was followed by a similar study in 2015, both of which consider the hypothesis that the impact exacerbated or induced the Deccan volcanism, since the events occurred approximately at [[antipodes]].<ref>{{cite journal |title=State shift in Deccan volcanism at the Cretaceous-Paleogene boundary, possibly induced by impact |date=2 October 2015 |journal=Science |volume=350 |issue=6256 |pages=76–78 |doi=10.1126/science.aac7549 |pmid=26430116 |last1=Renne |first1=P. R. |last2=Sprain |first2=C. J. |last3=Richards |first3=M. A. |last4=Self |first4=S. |last5=Vanderkluysen |first5=L. |last6=Pande |first6=K. |bibcode=2015Sci...350...76R|doi-access=free }}</ref><ref>{{cite web |title=Asteroid that killed dinosaurs also intensified volcanic eruptions - study |url=https://www.theguardian.com/science/2015/oct/01/asteroid-that-killed-dinosaurs-also-intensified-volcanic-eruptions-study |date=2 October 2015 |work=The Guardian |access-date=2 October 2015}}</ref> A 2020 study questioned the idea that the Deccan Traps were a contributory factor at all, suggesting that the Deccan Traps eruptions may have even partially negated the climatic change induced by the impact.<ref name=":5" />
A major criticism of the Deccan Traps as the primary cause of the extinctions is that the extinction event appears to be globally geologically instantaneous and simultaneous in both marine and terrestrial environments, as would be expected from an impact cause, rather than staggered as would be expected from an LIP cause.<ref name=":5" />
A more recent discovery appears to demonstrate the scope of the destruction from the impact alone, however. In a March 2019 article in the [[Proceedings of the National Academy of Sciences]], an international team of twelve scientists revealed the contents of the [[Tanis (fossil site)|Tanis fossil site]] discovered near [[Bowman, North Dakota]], that appeared to show a devastating mass destruction of an ancient lake and its inhabitants at the time of the Chicxulub impact. In the paper, the group reports that the geology of the site is strewn with [[fossil]]ized trees and remains of fish and other animals. The lead researcher, Robert A. DePalma of the [[University of Kansas]], was quoted in the New York Times as stating that "You would be blind to miss the carcasses sticking out... It is impossible to miss when you see the outcrop". Evidence correlating this find to the Chicxulub impact included [[tektite]]s bearing "the unique chemical signature of other tektites associated with the Chicxulub event" found in the gills of fish fossils and embedded in [[amber]], an [[iridium]]-rich top layer that is considered another signature of the event, and an atypical lack of evidence for scavenging, perhaps suggesting that there were few survivors. The exact mechanism of the site's destruction has been debated as either an impact-caused [[tsunami]] or lake and river [[seiche]] activity triggered by post-impact earthquakes, though there has yet been no firm conclusion upon which researchers have settled.<ref>{{Cite web|url=https://news.ku.edu/2019/03/29/stunning-discovery-offers-glimpse-minutes-following-%E2%80%98dinosaur-killer%E2%80%99-chicxulub-impact|title=Stunning discovery offers glimpse of minutes following 'dinosaur-killer' Chicxulub impact|date=29 March 2019|access-date=10 April 2019|archive-date=10 April 2019|archive-url=https://web.archive.org/web/20190410034107/https://news.ku.edu/2019/03/29/stunning-discovery-offers-glimpse-minutes-following-%E2%80%98dinosaur-killer%E2%80%99-chicxulub-impact|url-status=dead}}</ref><ref>{{Cite news|url=https://www.nytimes.com/2019/03/29/science/dinosaurs-extinction-asteroid.html |archive-url=https://ghostarchive.org/archive/20220101/https://www.nytimes.com/2019/03/29/science/dinosaurs-extinction-asteroid.html |archive-date=2022-01-01 |url-access=limited|title=Fossil Site Reveals Day That Meteor Hit Earth and, Maybe, Wiped Out Dinosaurs|date=29 March 2019|newspaper=The New York Times|last1=Broad|first1=William J.|last2=Chang|first2=Kenneth}}{{cbignore}}</ref>
A 2024 study of [[glycerol dialkyl glycerol tetraether]] levels in fossilized peat found that the Deccan Traps caused long-term warming of around 3°C over the course of the final 100,000 years of the [[Maastrichtian]], as well as about 5°C drop in temperature for less than 10,000 years around 30,000 years prior to the K-Pg boundary (coinciding with the peak of the Poladpur eruptive phase), but by the time of the K-Pg boundary, global temperatures had returned to previous levels. This suggests that the Deccan Traps were not the primary cause of extinction.<ref name=":7" />
==Petrology==
[[File:World geologic provinces.jpg|thumb|upright=1.3|The Deccan Traps shown as a dark purple spot on the geologic map of India]]
[[File:Epistilbite-Calcite-170550.jpg|thumb|Crystals of [[epistilbite]] and [[calcite]] in a [[vug]] in Deccan Traps basalt lava from Jalgaon District, Maharashtra]]Within the Deccan Traps, at least 95% of the lavas are [[tholeiitic basalt]]s.<ref>{{cite journal|last1=Aramaki|first1=S.|last2=Fukuoka|first2=T.|last3=Deshmukh|first3=S. S.|last4=Fujii|first4=T.|last5=Sano|first5=T.|date=2001-12-01|title=Differentiation Processes of Deccan Trap Basalts: Contribution from Geochemistry and Experimental Petrology|journal=Journal of Petrology|language=en|volume=42|issue=12|pages=2175–2195|doi=10.1093/petrology/42.12.2175|issn=0022-3530|doi-access=}}</ref> Major mineral constituents are [[olivine]], [[pyroxene]]s, and [[plagioclase]], as well as certain [[Iron|Fe]]-[[Titanium|Ti]]-rich oxides. These magmas are <7% [[Magnesium oxide|MgO]]. However, many of these minerals are observed as highly altered forms.<ref name=":0" /> Other rock types present include [[alkali basalt]], [[nephelinite]], [[lamprophyre]], and [[carbonatite]].
Mantle [[xenolith]]s have been described from [[Kachchh]] (northwestern India) and elsewhere in the western Deccan and contain spinel [[lherzolite]] and [[pyroxenite]] constituents.<ref name=":0" /><ref>{{cite journal|last1=Dessai|first1=A.G.|last2=Vaselli|first2=O.|date=October 1999|title=Petrology and geochemistry of xenoliths in lamprophyres from the Deccan Traps: implications for the nature of the deep crust boundary in western India|url=https://rruff.info/doclib/MinMag/Volume_63/63-5-703.pdf |archive-url=https://web.archive.org/web/20161215200622/http://rruff.info/doclib/MinMag/Volume_63/63-5-703.pdf |archive-date=2016-12-15 |url-status=live|journal=Mineralogical Magazine|volume=63|issue=5|pages=703–722|doi=10.1180/minmag.1999.063.5.08|bibcode=1999MinM...63..703D}}</ref>
While the Deccan traps have been categorized in many different ways including the three different [[Stratigraphy|stratigraphic]] groups, geochemically the province can be split into as many as eleven different formations. Many of the petrologic differences in these units are a product of varying degrees of crustal contamination.<ref name=":0" />
==Fossils==
[[File:Rajasaurus en las traps del decán.jpg|thumb|left|upright=1.1|[[Paleoart]] of the Deccan trap during the Late Cretaceous]]
The Deccan Traps are famous for the beds of fossils that have been found between layers of lava. Particularly well-known species include the frog ''[[Oxyglossus]] pusillus'' (Owen) of the [[Eocene]] of [[India]] and the toothed frog ''[[Indobatrachus]]'', an early lineage of modern frogs, which is now placed in the Australian family [[Myobatrachidae]].<ref>{{cite journal |last1= Noble |first1= Gladwyn Kingsley |author-link= Gladwyn Kingsley Noble |year= 1930 |title= The Fossil Frogs of the Intertrappean Beds of Bombay, India |journal= American Museum of Natural History |volume= 401 |page= 1930 |hdl= 2246/3061}}</ref><ref>{{cite web |url=http://tolweb.org/Myobatrachinae/16946 |title=Myobatrachinae |access-date=19 June 2011 |archive-date=22 September 2017 |archive-url=https://web.archive.org/web/20170922052151/http://tolweb.org/Myobatrachinae/16946 |url-status=dead }}</ref> The [[Infratrappean Beds]] (Lameta Formation) and [[Intertrappean Beds]] also contain fossil freshwater [[molluscs]].<ref>Hartman, J.H., Mohabey, D.M., Bingle, M., Scholz, H., Bajpai, S., and Sharma, R., 2006, Initial survivorship of nonmarine molluscan faunas in end-Cretaceous Deccan intertrappean strata, India: Geological Society of America (annual meeting, Philadelphia) Abstracts with Programs, v. 38, no. 7, p. 143.</ref>
==Theories of formation==
It is postulated<!-- {{by whom|date=November 2022}} see ref 'Basu,Renne,DasGupta' end of next sentence--> that the Deccan Traps eruption was associated with a deep [[mantle plume]]. High [[Helium-3|<sup>3</sup>He]]/[[Helium-4|<sup>4</sup>He]] ratios of the main pulse of the eruption are often seen in magmas with [[mantle plume]] origin.<ref>{{Cite journal|last1=Basu|first1=Asish R.|last2=Renne|first2=Paul R.|last3=DasGupta|first3=Deb K.|last4=Teichmann|first4=Friedrich|last5=Poreda|first5=Robert J.|date=1993-08-13|title=Early and Late Alkali Igneous Pulses and a High-3He Plume Origin for the Deccan Flood Basalts|url=https://www.science.org/doi/10.1126/science.261.5123.902|journal=Science|volume=261|issue=5123|pages=902–906|doi=10.1126/science.261.5123.902|pmid=17783739|bibcode=1993Sci...261..902B|s2cid=23709446|url-access=subscription}}</ref> The area of long-term eruption (the [[hotspot (geology)|hotspot]]), known as the [[Réunion hotspot]], is suspected of both causing the Deccan Traps eruption and opening the [[rift]] that separated the [[Mascarene Plateau]] from India. Regional [[crustal thinning]] supports the theory of this rifting event and likely encouraged the rise of the plume in this area.<ref name=":1" /> [[Seafloor spreading]] at the boundary between the Indian and [[African Plate]]s subsequently pushed India north over the plume, which now lies under [[Réunion]] island in the [[Indian Ocean]], southwest of India. The mantle plume model has, however, been challenged.<ref name="mantleplumes">Sheth, Hetu C. "[http://www.mantleplumes.org/Deccan.html The Deccan Beyond the Plume Hypothesis]." ''MantlePlumes.org,'' 2006.</ref>
Data continues to emerge that supports the plume model. The motion of the Indian tectonic plate and the eruptive history of the Deccan traps show strong correlations. Based on data from marine magnetic profiles, a pulse of unusually rapid plate motion began at the same time as the first pulse of Deccan flood basalts, which is dated at 67 million years ago. The spreading rate rapidly increased and reached a maximum at the same time as the peak basaltic eruptions. The spreading rate then dropped off, with the decrease occurring around 63 million years ago, by which time the main phase of Deccan volcanism ended. This correlation is seen<!-- {{by whom|date=November 2022}} ...see ref name=Cande--> as driven by plume dynamics.<ref name=Cande>{{cite journal | last1 = Cande | first1 = S.C. | last2 = Stegman | first2 = D.R. | year = 2011| title = Indian and African plate motions driven by the push force of the Réunion plume head | journal = Nature | volume = 475 | issue = 7354| pages = 47–52 | doi = 10.1038/nature10174 | pmid = 21734702 | bibcode = 2011Natur.475...47C | s2cid = 205225348 }}</ref>
The motions of the Indian and [[African Plate|African plates]] have also been shown<!-- {{by whom|date=November 2022}} ibid Cande--> to be coupled, the common element being the position of these plates relative to the ___location of the Réunion plume head. The onset of accelerated motion of India coincides with a large slowing of the rate of counterclockwise rotation of Africa. The close correlations between the plate motions suggest that they were both driven by the force of the Réunion plume.<ref name="Cande" />
When comparing the Na<sub>8</sub>, Fe<sub>8</sub>, and Si<sub>8</sub> contents of the Deccan to other major igneous provinces, the Deccan appears to have undergone the greatest degree of melting suggesting a deep plume origin. [[Olivine]] appears to have fractionated at near-[[Mohorovičić discontinuity|Moho]] depths with additional fractionation of [[gabbro]] ~6 km below the surface.<ref name=":0" /> Features such as widespread [[faulting]], frequent [[dike (geology)|diking]] events, high heat flux, and positive [[Gravity anomaly|gravity anomalies]] suggest that the extrusive phase of the Deccan Traps is associated with the existence of a triple junction which may have existed during the Late Cretaceous, having been caused by a deep mantle plume. Not all of these diking events are attributed to large-scale contributions to the overall flow volume. It can be difficult, however, to locate the largest dikes as they are often located towards the west coast and are therefore believed to currently reside under water.<ref name=":1" />
==Suggested link to impact events==
[[File:Deccan Traps volcano.jpg|The illustration of the Deccan Trap eruption that may have caused the extinction of the dinosaurs|thumb]]
===Chicxulub crater===
Although the Deccan Traps began erupting well before [[Chicxulub crater|the impact]], in a 2015 study it was proposed based on [[argon–argon dating]] that the impact may have caused an increase in permeability that allowed magma to reach the surface and produced the most voluminous flows, accounting for around 70% of the volume.<ref name=Richards2015>{{cite journal |last1=Richards|first1=Mark A. |last2=Alvarez|first2=Walter |last3=Self|first3=Stephen |last4=Karlstrom|first4=Leif |last5=Renne|first5=Paul R. |last6=Manga|first6=Michael |last7=Sprain|first7=Courtney J. |last8=Smit|first8=Jan |last9=Vanderkluysen|first9=Loÿc |last10=Gibson|first10=Sally A. |author-link2=Walter Alvarez |author-link5=Paul Renne |author-link6=Michael Manga |title=Triggering of the largest Deccan eruptions by the Chicxulub impact|journal=Geological Society of America Bulletin |volume=127|issue=11–12|pages=1507–1520 |doi=10.1130/B31167.1 |year=2015|bibcode=2015GSAB..127.1507R |s2cid=3463018 |url= http://eprints.esc.cam.ac.uk/3289/1/Gibson%20bul%20gsa.pdf |archive-url=https://web.archive.org/web/20180219045415/http://eprints.esc.cam.ac.uk/3289/1/Gibson%20bul%20gsa.pdf |archive-date=2018-02-19 |url-status=live}}</ref> The combination of the asteroid impact and the resulting increase in eruptive volume may have been responsible for the mass extinctions that occurred at the time that separates the Cretaceous and [[Paleogene]] periods, known as the [[K–Pg boundary]].<ref>{{cite journal |title=State shift in Deccan volcanism at the Cretaceous-Paleogene boundary, possibly induced by impact |last1=Renne |first1=P. R. |display-authors=etal |date=2015 |journal=Science |doi=10.1126/science.aac7549 |pmid= 26430116|volume=350 |issue=6256 |pages=76–78|bibcode=2015Sci...350...76R|doi-access=free }}</ref><ref>{{cite journal |last1=Sprain |first1=Courtney J. |last2=Renne |first2=Paul R. |last3=Vanderkluysen |first3=Loÿc |last4=Pande |first4=Kanchan |last5=Self |first5=Stephen |last6=Mittal |first6=Tushar |title=The eruptive tempo of Deccan volcanism in relation to the Cretaceous-Paleogene boundary |journal=Science |date=21 February 2019 |volume=363 |issue=6429 |pages=866–870 |doi=10.1126/science.aav1446 |pmid=30792301 |bibcode=2019Sci...363..866S|s2cid=67876911 |doi-access=free }}</ref> However this proposal has been questioned by other authors, who describe the suggestion as being "convenient interpretations based on superficial and cursory observations."<ref>{{Cite journal |last1=Dole |first1=Gauri |last2=Patil Pillai |first2=Shilpa |last3=Upasani |first3=Devdutt |last4=Kale |first4=Vivek S. |date=January 2017 |title=Triggering of the largest Deccan eruptions by the Chicxulub impact: Comment |url=https://pubs.geoscienceworld.org/gsabulletin/article/129/1-2/253-255/185478 |journal=Geological Society of America Bulletin |language=en |volume=129 |issue=1–2 |pages=253–255 |doi=10.1130/B31520.1 |bibcode=2017GSAB..129..253D |issn=0016-7606}}</ref>
===Shiva crater===
A geological structure that exists in the sea floor off the west coast of India has been suggested as a possible impact crater, in this context called the [[Shiva crater]]. It was also dated approximately 66 million years ago, potentially matching the Deccan traps. The researchers claiming that this feature is an impact crater suggest that the impact may have been the triggering event for the Deccan Traps as well as contributing to the acceleration of the Indian plate in the early [[Paleogene]].<ref>[[Sankar Chatterjee|Chatterjee, Sankar]]. "[https://gsa.confex.com/gsa/2003AM/finalprogram/abstract_58126.htm The Shiva Crater: Implications for Deccan Volcanism, India-Seychelles Rifting, Dinosaur Extinction, and Petroleum Entrapment at the KT Boundary] {{Webarchive|url=https://web.archive.org/web/20161202220808/https://gsa.confex.com/gsa/2003AM/finalprogram/abstract_58126.htm |date=2 December 2016 }}." Paper No. 60-8, Seattle Annual Meeting, November 2003.</ref> However, the current consensus in the Earth science community is that this feature is unlikely to be an actual impact crater.<ref name="Leslie2008a">{{cite web|author=Mullen, Leslie|date=2 November 2004|url=http://www.spacedaily.com/news/deepimpact-04r.html|title=Shiva: Another K–Pg Impact?|work=Spacedaily.com|access-date=20 February 2008}} - original article at [https://web.archive.org/web/20110804221725/http://www.astrobio.net/exclusive/1281/shiva-another-k-t-impact source]</ref><ref>{{cite web |url=http://www.space.com/scienceastronomy/091018-dinosaur-crater.html |title=New Dino-destroying Theory Fuels Hot Debate |first=Clara |last=Moskowitz |publisher=space.com |date=18 October 2009}}</ref>
==See also==
{{Portal|Geology}}
*[[Columbia River Basalt Group]]
*[[Emeishan Traps]]
*[[Geology of India]]
*[[Krishna Godavari Basin]]
*[[Lameta Formation]]
*[[List of flood basalt provinces]]
*[[List of volcanoes in India]]
*[[Siberian Traps]]
*[[Verneshot]]
*[[Late Devonian extinction#Magmatism|Viluy Traps]]
==References==
{{Reflist}}
==External links==
{{Commons category}}
*{{cite web |url=http://www.geodynamics.no/indexOld.htm |title=Animated simulation by the Geodynamics group at the Geological Survey of Norway illustrating the Indian plate moving through the Indian Ocean |url-status=dead |archive-url=https://web.archive.org/web/20110723122146/http://www.geodynamics.no/indexOld.htm |archive-date=23 July 2011}}
*[https://www.nbcnews.com/id/wbna50119631 Scientist argues that volcanoes, not meteorite, killed dinosaurs]
*[https://hoopermuseum.carleton.ca/saleem/volcanism.htm The Deccan Traps/Volcanism Theory]
{{coord|18|51|N|73|43|E|region:IN_type:landmark_scale:2500000|display=title}}
{{Large igneous provinces}}
[[Category:Cretaceous paleontological sites of Asia]]
[[Category:Cretaceous–Paleogene boundary]]
[[Category:Cretaceous volcanism]]
[[Category:Events that forced the climate]]
[[Category:Geology of India]]
[[Category:Geology of Maharashtra]]
[[Category:Large igneous provinces]]
[[Category:Paleocene volcanism]]
[[Category:Plate tectonics]]
[[Category:Volcanism of India]]
| |||