托福听力背景知识：考古年代的测定

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托福听力背景知识:考古年代的测定
DatingMethodsinArchaeology
Ifthereisonefundamentalissueonwhichmostarchaeologistscangenerallyagree,itistheimportanceofchronologyinstudyingthepast.Althoughoneofthemostimportantcontributionsthatarchaeologycanmakeisthestudyofculturesoverlongtimespans,controlofthetimedimensioniscrucialinalmostallkindsofarchaeologicalrearch.Instudyingthearchaeologicalrecord,thearchaeologistneedstodifferentiatethomaterialsthatarecontemporaryandthothatreflectthepassageoftime.Giventheimportanceofestablishingthetemporalrelationshipsofarchaeologicalremains,itisnotsurprisingthatuntiltheintroductionofdatingtechniquesfromthephysicalsciences(e.g.,chemistryandnuclearphysics),issuesofchronologydominatedarchaeology.Archaeologistscannowaccessawidevarietyoftechniquestoestimatetheageofarchaeologicalremains,andcannowturntheirattentiontoissuesotherthanchronology.
Thedatingmethodsudbyarchaeologistsvaryconsiderablyinprecisionandthenatureofthematerialactuallydated.Agedeterminationsforarchaeologicalmaterialsmaybedirectorindirect.Directdatesarederivedfromtheactualartifact,featureorecofacttodeterminetheageofthematerial.Indirectdatesarebadonmaterialassociatedwiththearchaeologicalitemofinterest.Forexample,ashinanancienthearthcanbedatedbytheradiocarbondatingmethod(discusdbelow)andothermaterial,suchaspottery,stonetools,andfragmentsofanimalboneassociatedwiththehearth,canthenbeindirectlyassignedthesameage.Thisassignment,however,assumesthatthereissufficientevidenceindicatingthatboththehearthandtheartifactsreflectthesamecontemporaneouvent,thusallowingtheextensionofthedirectdatetotheotherrelatedmaterial.
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Datesmayberelativeorabsoluteintheirscaleofmeasurement.Relativedatingsimplyordersremainsintoarankedchronologicalquence,wheretheageofeachisrelative(i.e.,earlierthanlaterthan,orcontemporary)totheothers.Thepreliminarystepsinmostarchaeologicalrearchusuallyemployrelativedatingmethodstoorderartifacts,featuresandsitesintotemporalquences.Absolutedatingprovidesaspecificcalendarageestimate(e.g.,1000yearsago),thusallowingdeterminationoftheactualamountoftimedifferencebetweenabsolutedates.Althoughabsolutedatesprovideacalendarage,theyvaryintheirprecision,asmanyhaveanuncertaintyfactorattachedthatindicatesarangeoftimeratherthanaspecificdate.
Althoughdatingmethodsareudtodeterminetheageofobjectsandevents,thedatesareorderedtoestablishachronologythatprovidesatemporalframeworkinwhichthearchaeologicalmaterialcanbeplaced.Thischronologybuildingprocessisthefoundationforarchaeologicalstudies.Inthischapter,weexaminesomeofthemajortechniquesthathavebeendevelopedtodatethearchaeologicalpastandmaterialfromthearchaeologicalrecord