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地球学报 2012
泰国东北部猜也奔府NoenSa-nga地区Yasothon土壤剖面中的澳大拉西亚玻陨石Keywords: Australasiantektite,Yasothonsoilseries,Meteoriticimpact,NortheasternThailand Abstract: AsedimentaryprofileexposedinsoilquarriesafewkilometersnorthofNoenSa-ngadistrict,Chaiyaphumprovince,NEThailand,revealsaQuaternarygeologicalhistory.Thelowerpartofthesoilprofileisagraveldepositcharacterizedbysub-angulartowell-roundedpebblesrepresentinganabandonedriversedimentarydeposit.Thegravelbedinsomeplacesiscoatedbyironoxideasathinlayerofferricreteattheuppermostpart.Theupperpartofthesoilprofileisabrightreddishbrownstructurelesssanddepositwithfiningupwardsedimentarystructureatthebasalportion,theYasothonsoilseries.Apieceoftektitewasdiscoveredatthecontactboundarybetweenthetwosedimentaryunits.Itischaracterizedbyanirregularshapewithasmoothconcavedsurfaceregardingasanexternalmoldofapieceofwell-roundedpebble.Thispieceoftektiteindicatesthatasolidifiedtektitehadfallenfromhighskythenwasremeltedintoaplasticformpriortoreachandpartlycoverapieceofwell-roundedpebble.Theseevidencessuggestthattherewasameteoriticorcometaryimpactonourearthsurfacesomewhereintheregionthencatapultednumbersofmeltedsilicaejectawithvastvolumeofdustintothesky.Themeltedsilicaejectaweresolidifiedintosplash-formtektiteswithvariousshapeswhiletheywereinthehighsky.Afterthatthetektiteshadfallendownandremeltedintoaplasticformpriortoreachthegroundsurfaceandthensolidifiedasatektitedepositfollowedbylarger-sizedsedimentsandangularquartzfragmentsformingafiningupwardsedimentarystructure.Thefinersedimentsweregraduallysettleddownformingabrightreddishbrownstructurelesssanddeposit,theYasothonsoilseries.Thismeteoriticimpacteventoccurredatabout0.77Maagoastheevidenceoftheprevioustektiteradiometricdating.
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