Editing Chicxulub crater (section)

==Geology==

===Pre-impact geology===
[[File:Chicxulub Wharf Yucatan Mexico.jpg|thumb|alt=An image of a boardwalk over a body of water. A sign says "Chicxulub Puerto Mexico"| The center of the crater is near [[Chicxulub Puerto]].|right]]
[[File:Chicxulub Puerto.jpg|right|thumb|[[Stele|Stela]] in the main square of Chicxulub Puerto commemorating the impact]]
Before the impact, the geology of the [[Yucatán Platform|Yucatán area]], sometimes referred to as the "target rocks", consisted of a sequence of mainly Cretaceous limestones, overlying [[red bed]]s of uncertain age above an unconformity with the dominantly granitic [[basement (geology)|basement]]. The basement forms part of the [[Maya Block]] and information about its makeup and age in the Yucatán area has come only from drilling results around the Chicxulub crater and the analysis of basement material found as part of the ejecta at more distant K–Pg boundary sites. The Maya block is one of a group of crustal blocks found at the edge of the [[Gondwana]] continent. [[Zircon]] ages are consistent with the presence of an underlying [[Grenvillian orogeny|Grenville]] age crust, with large amounts of late [[Ediacaran]] [[Volcanic arc|arc]]-related [[igneous rock]]s, interpreted to have formed in the [[Pan-African orogeny]]. Late [[Paleozoic]] [[granitoid]]s (the distinctive "pink granite") were found in the peak ring borehole M0077A, with an estimated age of 326 ± 5 million years ago ([[Carboniferous]]). These have an [[adakite|adakitic]] composition and are interpreted to represent the effects of [[slab detachment]] during the [[Ouachita orogeny|Marathon-Ouachita orogeny]], part of the collision between [[Laurentia]] and Gondwana that created the [[Pangaea]] [[supercontinent]].<ref name="Zhao_etal_2020">{{Cite journal |last1=Zhao |first1=J. |last2=Xiao |first2=L. |last3=Gulick |first3=S.P.S. |last4=Morgan |first4=J.V.|author4-link= Joanna Morgan |last5=Kring |first5=D. |last6=Urrutia-Fucugauchi |first6=J. |last7=Schmeider |first7=M. |last8=de Graaf |first8=S.J. |last9=Wittmann |first9=A. |last10=Ross |first10=C.R. |last11=Claeys |first11=P. |last12=Pickersgill|first12=A.|last13=Kaskes|first13=P.|last14=Goderis|first14=S.|last15=Rasmussen|first15=C.|last16=Vajda|first16=V.|last17=Ferrière|first17=L.|last18=Fiegnon|first18=J.-G.|last19=Yamagucho|first19=K.|display-authors=3|year=2020 |title=Geochemistry, geochronology and petrogenesis of Maya Block granitoids and dykes from the Chicxulub Impact Crater, Gulf of México: Implications for the assembly of Pangea |journal=Gondwana Research |volume=82 |pages=128–150 |doi=10.1016/j.gr.2019.12.003|bibcode=2020GondR..82..128Z |s2cid= 214359672|url=https://biblio.vub.ac.be/vubirfiles/78237141/Zhao_etal_accepted.pdf }}</ref>

Red beds of variable thickness, up to {{convert|115|m|sp=us}}, overlay the granitic basement, particularly in the southern part of the area. These continental [[clastic rock]]s are thought to be of [[Triassic]]-to-Jurassic age, although they may extend into the [[Lower Cretaceous]]. The lower part of the Lower Cretaceous sequence consists of [[Dolomite (rock)|dolomite]] with interbedded anhydrite and gypsum, with the upper part being limestone, with dolomite and anhydrite in part. The thickness of the Lower Cretaceous varies from {{convert|750|m|sp=us}} up to {{convert|1675|m|sp=us}} in the boreholes. The [[Upper Cretaceous]] sequence is mainly platform limestone, with [[marl]] and interbedded anhydrite. It varies in thickness from {{convert|600|m|sp=us}} up to {{convert|1200|m|sp=us}}. There is evidence for a Cretaceous basin within the Yucatán area that has been named the Yucatán Trough, running approximately south–north, widening northwards, explaining the observed thickness variations.<ref name="Guzman_Hidalgo_etal_2021">{{Cite journal |last1=Guzmán-Hidalgo |first1=E. |last2=Grajales-Nishimura |first2=J.M. |last3=Eberli |first3=G.P. |last4=Aguayo-Camargo |first4=J.E. |last5=Urrutia-Fucugauchi |first5=J. |last6=Pérez-Cruze |first6=L. |display-authors=3|year=2021 |title=Seismic stratigraphic evidence of a pre-impact basin in the Yucatán Platform: morphology of the Chicxulub crater and K/Pg boundary deposits |journal=Marine Geology |volume=441 |page=106594 |doi=10.1016/j.margeo.2021.106594|bibcode=2021MGeol.44106594G |s2cid=238783773}}</ref>

===Impact rocks===
The most common observed [[impactite|impact rocks]] are [[suevite]]s, found in many of the boreholes drilled around the Chicxulub crater. Most of the suevites were resedimented soon after the impact by the resurgence of oceanic water into the crater. This gave rise to a layer of suevite extending from the inner part of the crater out as far as the outer rim.<ref name="Kaskes_etal_2022">{{Cite journal |last1=Kaskes |first1=P. |last2=de Graaf |first2=S.J. |last3=Feignon |first3=J.-G. |last4=Déhais |first4=T. |last5=Goderis |first5=S. |last6=Ferrière |first6=LO. |last7=Koeberl |first7=C. |last8=Smit |first8=J. |last9=Wittmann |first9=A. |last10=Gulick |first10=S.P.S. |last11=Debaille |first11=V. |last12=Mattielli|first12=N.|last13=Claeys|first13=P.|display-authors=3|year=2022 |title=Formation of the crater suevite sequence from the Chicxulub peak ring: A petrographic, geochemical, and sedimentological characterization |journal=GSA Bulletin |volume=134 |issue=3–4 |pages=895–927 |doi=10.1130/B36020.1|bibcode=2022GSAB..134..895K |s2cid=237762081|url=https://biblio.vub.ac.be/vubirfiles/72890608/b36020.pdf }}</ref>

Impact melt rocks are thought to fill the central part of the crater, with a maximum thickness of {{convert|3|km|sp=us}}. The samples of melt rock that have been studied have overall compositions similar to that of the basement rocks, with some indications of mixing with carbonate source, presumed to be derived from the Cretaceous carbonates. An analysis of melt rocks sampled by the M0077A borehole indicates two types of melt rock, an upper impact melt (UIM), which has a clear carbonate component as shown by its overall chemistry and the presence of rare limestone clasts and a lower impact melt-bearing unit (LIMB) that lacks any carbonate component. The difference between the two impact melts is interpreted to be a result of the upper part of the initial impact melt, represented by the LIMB in the borehole, becoming mixed with materials from the shallow part of the crust either falling back into the crater or being brought back by the resurgence forming the UIM.<ref name="de Graaf_etal_2022">{{Cite journal |last1=de Graaf |first1=S.J. |last2=Kaskes |first2=P. |last3=Déhais |first3=T. |last4=Goderis |first4=S. |last5=Debaille |first5=V. |last6=Ross |first6=C.H. |last7=Gulick |first7=S.P.S. |last8=Feignon |first8=J.-G. |last9=Ferrière |first9=L. |last10=Koeberi |first10=C. |last11=Smit |first11=J. |last12=Mattielli |first12=N. |last13=Claeys |first13=P. |display-authors=3 |year=2022 |title=New insights into the formation and emplacement of impact melt rocks within the Chicxulub impact structure, following the 2016 IODP-ICDP Expedition 364 |journal=GSA Bulletin |volume=134 |issue=1–2 |pages=293–315 |doi=10.1130/B35795.1 |bibcode=2022GSAB..134..293D |s2cid=236541913 |url=https://biblio.vub.ac.be/vubirfiles/79061460/deGraaff_ImpactMelt_GSA_B_Manuscript_v3_MasterFile_Clean.pdf |access-date=May 18, 2022 |archive-date=May 18, 2022 |archive-url=https://web.archive.org/web/20220518033352/https://biblio.vub.ac.be/vubirfiles/79061460/deGraaff_ImpactMelt_GSA_B_Manuscript_v3_MasterFile_Clean.pdf |url-status=live }}</ref>

The "pink granite", a granitoid rich in [[alkali feldspar]] found in the peak ring borehole shows many deformation features that record the extreme strains associated with the formation of the crater and the subsequent development of the peak ring.<ref name="Kring_2017" /><ref>{{cite news|last1=St. Fleur|first1=Nicholas|title=Drilling into the Chicxulub Crater, Ground Zero of the Dinosaur Extinction|url=https://www.nytimes.com/2016/11/18/science/chicxulub-crater-dinosaur-extinction.html|newspaper=The New York Times|date=November 17, 2016|access-date=March 1, 2017|archive-date=November 19, 2016|archive-url=https://web.archive.org/web/20161119200501/http://www.nytimes.com/2016/11/18/science/chicxulub-crater-dinosaur-extinction.html?_r=0|url-status=live}}</ref> The granitoid has an unusually low density and [[P-wave]] velocity compared to typical granitic basement rocks. Study of the core from M0077A shows the following deformation features in apparent order of development: pervasive fracturing along and through grain boundaries, a high density of [[shear fault]]s, bands of [[cataclasite]] and ultra-cataclasite and some [[shear zone|ductile shear structures]]. This deformation sequence is interpreted to result from initial crater formation involving [[acoustic fluidization]] followed by shear faulting with the development of cataclasites with [[fault zone]]s containing impact melts.<ref name="Riller_etal_2018">{{Cite journal |last1=Riller |first1=U. |last2=Poelchau |first2=M.H. |last3=Rae |first3=A.S.P. |last4=Schulte |first4=F.M. |last5=Collins |first5=G.S. |last6=Melish |first6=H.J. |last7=Grieve |first7=R.A.F. |last8=Morgan |first8=J.V.|author8-link= Joanna Morgan |last9=Gulick |first9=S.P. |last10=Lofi |first10=J. |last11=Diaw |first11=A. |last12=McCall|first12=N.|last13=Kring|first13=D.A.|last14=((IODP–ICDP Expedition 364 Science Party))|display-authors=3|year=2018 |title=Rock fluidization during peak-ring formation of large impact structures |journal=Nature |volume=562 |issue=7728 |pages=511–518 |doi=10.1038/s41586-018-0607-z|pmid=30356184 |bibcode=2018Natur.562..511R |s2cid=53026325|url=http://eprints.gla.ac.uk/173925/1/173925.pdf }}</ref>

The peak ring drilling below the sea floor also discovered evidence of a massive hydrothermal system, which modified approximately {{nowrap|1.4 × 10<sup>5</sup> km<sup>3</sup>}} of Earth's crust and lasted for hundreds of thousands of years. These hydrothermal systems may provide support for the impact origin of life hypothesis for the [[Hadean]] eon,<ref>{{cite journal<!--|authors=David A. Kring; Sonia M. Tikoo; Martin Schmieder1; Ulrich Riller; Mario Rebolledo-Vieyra; Sarah L. Simpson; Gordon R. Osinski; Jérôme Gattacceca; Axel Wittmann; Christina M. Verhagen; Charles S. Cockell; Marco J.L. Coolen; Fred J. Longstaffe; Sean P. S. Gulick; [[Joanna Morgan|Joanna V. Morgan]]; Timothy J. Bralower; Elise Chenot; Gail L. Christeson; Philippe Claeys; Ludovic Ferrière; Catalina Gebhardt; Kazuhisa Goto; Sophie L. Green; Heather Jones; Johanna Lofi; Christopher M. Lowery; Rubén Ocampo-Torres; Ligia Perez-Cruz; Annemarie E. Pickersgill; Michael H. Poelchau; Auriol S.P. Rae11; Cornelia Rasmussen; Honami Sato; Jan Smit; Naotaka Tomioka; Jaime Urrutia-Fucugauchi; Michael T. Whalen; Long Xiao and Kosei E. Yamaguchi-->|last1=Kring |first1=David |first2=Sonia M. |last2=Tikoo |first3=Martin |last3=Schmieder |display-authors=etal|title=Probing the hydrothermal system of the Chicxulub impact crater|journal=Science Advances |year=2020|volume=6|issue=22|doi=10.1126/sciadv.aaz3053|s2cid=219244669}}</ref> when the entire surface of Earth was affected by impactors much larger than the Chicxulub impactor.<ref>{{cite journal |first2= W.F. |last2=Bottke |first3=L.T. |last3=Elkins-Tanton |first4=M. |last4=Bierhaus|first5= K. |last5=Wuennemann|first6=A. |last6=Morbidelli |first7=D.A. |last7=Kring|last1=Marchi |first1=S. |display-authors=3|title=Widespread mixing and burial of Earth's Hadean crust by asteroid impacts|journal=Nature|year=2014|volume=511|issue=7511 |pages=578–582|doi=10.1038/nature13539|pmid=25079556 |bibcode=2014Natur.511..578M |s2cid=205239647}}</ref>

===Post-impact geology===
After the immediate effects of the impact had stopped, [[sedimentation]] in the Chicxulub area returned to the shallow water platform carbonate [[depositional environment]] that characterised it before the impact. The sequence, which dates back as far as the [[Paleocene]], consists of [[marl]] and limestone, reaching a thickness of about {{convert|1000|m|abbr=on}}.<ref name="Hildebrand et al_1991-09" />{{rp|3}} The K–Pg boundary inside the crater is significantly deeper than in the surrounding area.<ref name="Hildebrand et al_1991-09" />{{rp|4}}

On the Yucatán peninsula, the inner rim of the crater is marked by clusters of cenotes,<ref>{{cite magazine |url=https://www.youtube.com/watch?v=dNRTtLLuNM8 |type=video |title=Meteor impact site |series=Earth: The biography |magazine=National Geographic |date=July 11, 2008 |access-date=August 19, 2015 |archive-date=October 17, 2015 |archive-url=https://web.archive.org/web/20151017002003/https://www.youtube.com/watch?v=dNRTtLLuNM8 |url-status=live }}</ref> which are the surface expression of a zone of preferential groundwater flow, moving water from a recharge zone in the south to the coast through a [[karst]]ic [[aquifer]] system.<ref name="Hildebrand et al_1991-09" />{{rp|4}}<ref name="Pérez-Ceballos_etal_2021">{{Cite journal |last1=Pérez-Ceballos |first1=R. |last2=Canul-Macario |first2=C. |last3=Pacheco-Castro |first3=R. |last4=Pacheco-Ávila |first4=J. |last5=Euán-Ávila  |first5=J. |last6=Merino-Ibarra  |first6=M. |display-authors=3|year=2021 |title=Regional Hydrogeochemical Evolution of Groundwater in the Ring of Cenotes, Yucatán (Mexico): An Inverse Modelling Approach |journal=Water |volume=13 |issue=5 |page=614 |doi=10.3390/w13050614 |doi-access=free }}</ref> From the cenote locations, the karstic aquifer is clearly related to the underlying crater rim,<ref>{{cite web|author=Kring, David A.|work=lpl.arizona.edu|url=http://www.lpl.arizona.edu/SIC/impact_cratering/Chicxulub/Discovering_crater.html|title=Discovering the Crater|access-date=October 12, 2007|archive-url=https://web.archive.org/web/20071010021337/http://www.lpl.arizona.edu/SIC/impact_cratering/Chicxulub/Discovering_crater.html|archive-date=October 10, 2007}}</ref> possibly through higher levels of fracturing,
caused by [[Compaction (geology)#Differential compaction|differential compaction]].<ref name="Hildebrand_etal_1998">{{Cite book |last1=Hildebrand |first1=A.R.|last2=Pilkington|first2=M.|last3=Ortiz-Aleman|first3=C.|last4=Chavez|first4=R.E.|last5=Urrutia-Fucugauchi|first5=J.|last6=Connors|first6=M.|last7=Graniel-Castro|first7=E.|last8=Camara-Zi|first8=A.|last9=Halfpenny|first9=J.F.|last10=Niehaus|first10=D. |title=Meteorites: Flux with Time and Impact Effects |publisher=Geological Society |year=1998 |isbn=9781862390171 |display-authors=3|editor-last=Grady |editor-first=M.M. |series=Special Publications |volume=140 |publication-place=London |pages=160 |chapter=Mapping Chicxulub crater structure with gravity and seismic reflection data |doi=10.1144/GSL.SP.1998.140.01.12 |s2cid=130177601 |editor-last2=Hutchinson |editor-first2=R. |editor-last3=McCall |editor-first3=G.J.H. |editor-last4=Rothery |editor-first4=D.A.}}</ref>