Evolu&onofCaribbeansubduc&onfromP-wavetomographyandplatereconstruc&on

VoiLA

www.voila.ac.uk

RobAllen1,BenediktBraszus2,SaskiaGoes1,AndreasRietbrock2,JennyCollier1andVoiLAteam(NickHarmon3,

TimHenstock3,StephenHicks1,3,KateRychert3,BenMaunder1,JeroenvanHunen5,LidongBie2,JonBlundy4,GeorgeCooper4,5,RichardDavy1,MikeKendall4,Colin

Macpherson5,JamieWilkinson1,6,andMarjorieWilson7)

•  CaribbeansubducIongovernedtectonicevoluIon,associatedhazardsanddistribuIonnaturalresources.•  OneofonlytwozonesthatsubductsAtlanIcseafloor,formedbyslow-spreading,aglobalendmember

ofoldoceaniclithospheresubducIngatslowspeeds.•  PoorlyunderstoodsubducIonhistoryinvolvingchangesinlengthandshapeofthetrenchandseveral

generaIonsofarcs.

•  InourVolaIleRecyclingintheLesserAnIlles(VoiLA)project,weinstalledthefirstocean-boUomseismometer(OBS)networkintheregion(redtriangles,Fig.1).Usingthesedata,weimproveimagingoftheeasternCaribbeanuppermantleusingteleseismicPwaves,

•  WecompareimagedfragmentsofsubductedplatewithsubducIonlocaIonspredictedfromarecentlypublishedplatereconstrucIon.

Background

PlatereconstrucIon

Conclusions

ReconstrucIon:Mülleretal.(Tectonics,2019)updatedasfollows:(1)improvedgeometryofAtlanIcopeningboundaries(2)Proto-CaribbeanopeningwasreconstructedusinganimprovedgeometryoftheridgebetweenNorthandSouthAmericaandassumingsymmetricspreading

90Ma–earlystageofsubducIonalongGreatArcoftheCaribbean(GAC),whileProto-CaribbeanridgewasacIvelyspreading=>formingtwoslabs

70Ma–northernandsouthernpartsoftheGACmigrateoutwardstosubducttheoldestProto-Caribbeanlithosphere,accompaniedbyback-arcspreadingintheYucatán(YB)andVenezualan(VB)Basins.Proto-Caribbeanridgestopsspreading.Fz1,Fz2,Fz3arehypotheIcalfracturezones50Ma–northern(Cuban)segmentofGACinacIveaderdockingagainsttheBahamasBank,andback-arcspreadinginiIatedintheGrenadaBasin(GB),allowingtheacIvearctomoveeastwardstotheOuterAnIlleanArc(OAA).

30Ma–subducIonofthelarge-offsetfracturezoneattheeasternendoftheProto-Caribbean(markedasFz1on70MamaphasledtoarapidyoungingofthesubducIngslab,inducingaforwardjumpoftheacIvearctothecurrentLesserAnIlleanArc(LAA)

modelVoiLA-P19:Jointinversionofdatafromregionalseismicnetworks(VoiLAexperimentandaddiIonallandstaIonsonFig.1)togetherwiththehighestqualitydatafromtheglobalEHBcatalogue[Engdahletal.,BSSA1998],usingthemethodofWidiyantoriandvanderHilst(GJI1997)whereafineregionalgridisembeddedinacoarserglobalgrid.

Acknowledgments:FundedbyNERCconsorKumgrant(NE/K010824/1).ThankstoallwhosailedoncruisesRRSJamesCookJC133andJC149,ourpartnersattheUniversityofWestIndiesSeismicResearchCentre(SRC),theGermanInstrumentPoolforAmphibianSeismology(DEPAS),andUCSD(Scripps)forprovidingocean-bo\omseismometers.

Aims

Fig.1

Fig.2

Fig.5

•  IneasternCaribbeanuppermantle,materialsubductedatdifferenttrenchesfrom70MahasaccumulatedinsimilarlocaIonduetowestwardmovementoftheAmericas.

•  100-120MaslabintheshallowlowermantlebelownortheasternSouthAmericaconsistentwithstartofGACsubduc&onpriortothemostsignificantphaseofCLIPplumevolcanism

•  SlabgapsfoundatthelocaIonoftheProto-Caribbeanspreadingridge,detachmentofthenorthernGACslabaderCubadockedwithNorthAmerica,andalateraltearbelowGrenada,likelyalongaProto-Caribbeanfracturezone.

•  NAM-SAMplateboundaryisyettostartsubducIng,butsubduedanomalies(arrowsFig3b)maycorrespondtohydratedplate-domainboundarybetweenlithosphereformedinProto-CaribbeanandthatformedinEquatorialAtlanIc.

Fig.4

Fig.3

Uppermantle:Goodmatchbetweenobservedhighvelocityanomaliesandreconstructedtrencheswithslabsinkingrateof~1cm/yr,consistentwithconvergenceratesalongtheCaribbeansubducIonzones.•  Above~200kmdepth,high

velociIescorrespondtoposiIonofsubducIonalongLesserAnIllesArc(LAA),

•  between~250-450kmcorrespondtosubducIonalongtheOuterAnIllesArc(OAA),

•  inthetransiIonzonetothesouthern(sG)andnorthern(nG)partoftheGreatArcoftheCaribbean.–posiIonofexInctProto-Caribbeanspreadingcentre,aweaknesszone,whereweproposetheGACslabtoreintotwoslabsegments

•  sG2maybeasegmentofthesGslabshearedoffagainstSouthAmericanconInentalkeel

Inthelowermantle,ourpredictedslabposiIonsagreewellwithtwoanomaliesbelownorth-easternSouthAmerica,asimagedbyVanBenthemetal.(JGR,2013).SlabssubductedatthenorthernandsouthernGACwereseparatedbytheatthisImeacIveproto-Caribbeanridge()

P-wavetomography

1ImperialCollegeLondon,2KarlsruheInsItuteofTechnology,3UniversityofSouthampton,4UniversityofBristol,5DurhamUniversity,6NaturalHistoryMuseumLondon,7UniversityofLeeds

~250-350km

~200km

EGU2020-9018©Authors–allrightsreserved