简介：Evidenceforamantleand/orbasalticcomponentinKTboundarydistalejectaisapparentlyinconsistentwithejectionfromChicxulubCratersinceitislocatedon~35kmthickcontinentalcrust(DePaoloetal.,1983;Montanarietal.,1983;HildebrandandBoynton,1988,1990).Evidenceformafic/ultramafictargetrockswasreinforcedbydiscoveryofchromites,somewithshockplanardeformationfeatures(PDF),inimpactlayersamplesfromsitesinsouthernColoradoandeasternWyoming(Bohoretal.,1990).However,untilnowitwasunclearwhetherthechromitesoriginatedwithanimpactororwithterrestrialtargetrocks.Tothisend,high-precision54Cr/52CrisotoperatiosweremeasuredonKTboundarychromitesalongwithknownterrestrialchromites.Wefindaterrestrial54Cr/52CrratioinKTboundarychromitesfromimpactlayersamplescollectedattheabovesitesoverthelastseveralyears(Fig.1).Ejectedterrestrialchromitessuggesttheimpactsampledterrestrialmaficand/orultramafictargetrocksnotknowntoexistintheChicxulubtargetarea.

简介：Evidenceforamantleand/orbasalticcomponentinKTboundarydistalejectaisapparentlyinconsistentwithejectionfromChicxulubCratersinceitislocatedon~35kmthickcontinentalcrust(DePaoloetal.,1983;Montanarietal.,1983;HildebrandandBoynton,1988,1990).Thisevidence,alongwithejectedterrestrialchromites(Oldsetal.,2016)suggesttheimpactsampledterrestrialmaficand/orultramafictargetrockswhicharenotknowntoexistintheChicxulubtargetarea.Possibleresolutionstotheparadoxare:1)theexistenceofanunmapped/unknownsutureinYucatanPlatformbasement,2)anadditionalsmallunmapped/unknownimpactsiteonoceaniclithosphere,or3)anadditionallargeimpactonoceaniclithosphereorcontinentalmargintransitionaltooceaniclithosphere.Thethirdhypothesisiselaboratedheresince:1)OphiolitesnearesttoChicxulubcraterarefoundinCubaandapparentlywereobductedinlatestCretaceous/earliestDaniantimes(García-Casco,2008),inconsistentwiththedocumentedEocenecollisionofCubawiththeBahamasplatform;and2)Cubahoststheworld’sthickestknownKTboundarydeposits(Iturralde-Vinent,1992;Kiyokawaetal.,2002;Tadaetal.,2003).Theseandgeometricconsiderationssuggestoceaniccrustanduppermantlerock,exposedasophioliteintheGreaterAntillesislandchain,markstherimofaroughly700kmdiameterimpactbasindeformedanddismemberedfromanoriginallycircularformbyatleast50millionyearsofleft-lateralsheardisplacementalongtheNorthAmerican-Caribbeantransformplateboundary.

简介：摘要：通过对广东韶新高速公路某标段隧道初期支护特大围岩涌水的原因进行分析，确定采用 KT-CSS控制灌浆工法：低压、慢灌、快速固化、分序分次控制灌浆，利用水泥基类特种灌浆材料复合灌浆，解决了隧道初期支护特大涌水的问题。该涌水治理也对高速公路隧道安全掘进施工、地表水土流失治理和后期隧道二衬安全浇筑起到了十分积极的作用。