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老托福阅读100解析资料汇总.docx

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老托福阅读100解析资料汇总PerhapsoneofthemostdramaticandimportantchangesthattookplaceintheMesozoiceraoccurredlateinthatera,amongthesmallorganismsthatpopulatetheuppermost,sunlitportionoftheoceanstheplankton.Theterm"plankton"isabroadone,designatingallofthesmallplantsandanimalsthatfloataboutorweaklypropelthemselvesthroughthesea.InthelatestagesoftheMesozoicera,duringtheCretaceousperiod,therewasagreatexpansionofplanktonthatprecipitatedskeletonsorshellscomposedoftwotypesofmineral:silicaandcalciumcarbonate.Thisdevelopmentradicallychangedthetypesofsedimentsthataccumulatedontheseafloor,because,whiletheorganicpartsoftheplanktondecayedaftertheorganismsdied,theirmineralizedskeletonsoftensurvivedandsanktothebottom.ForthefirsttimeintheEarth'slonghistory,verylargequantitiesofsilicaskeletons,whichwouldeventuallyhardenintorock,begantopileupinpartsofthedeepsea.Thickdepositsofcalcareousoozemadeupofthetinyremainsofthecalciumcarbonate-secretingplanktonalsoaccumulatedasneverbefore.ThefamouswhitechalkcliffsofDover,inthesoutheastofEngland,arejustoneexampleofthehugequantitiesofsuchmaterialthatamassedduringtheCretaceousperiod;therearemanymore.JustwhythecalcareousplanktonweresoprolificduringthelatterpartoftheCretaceousperiodisnotfullyunderstood.Suchmassiveamountsofchalkysedimentshaveneversincebeendepositedoveracomparableperiodoftime.ThehighbiologicalproductivityoftheCretaceousoceansalsoledtoidealconditionsforoilaccumulation.Oilisformedwhenorganicmaterialtrappedinsedimentsisslowlyburiedandsubjectedtoincreasedtemperaturesandpressures,transformingitintopetroleum.SedimentsrichinorganicmaterialaccumulatedalongthemarginsoftheTethysSeaway,thetropicaleast-westoceanthatformedwhenEarth'ssinglelandmass(knownasPangaea)splitapartduringtheMesozoicera.Manyoftoday'simportantoilfieldsarefoundinthosesedimentsinRussia,theMiddleEast,theGulfofMexico,andinthestatesofTexasandLouisianaintheUnitedStates.托福阅读文章类型有哪几类学术性文章的篇章结构在学术性文章中一般需要具备三个组成部分：(1)Topic话题即文章的主角是什么，比如讲解某个科学理论、研究某种社会现象，探讨某个历史事件;在托福文章中这种导入性信息往往出现在篇首位置，考生可以根据篇首段信息对整