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1、第三章三角洲沉积体系DELTASYSTEMS第一节三角洲的环境特点及其沉积作用第二节三角洲的沉积特征及沉积模式第三节古代三角洲沉积鉴别标志及其与油气资源的关系第二节三角洲的沉积特征及沉积模式一、曲流河三角洲沉积体系二、辫状河三角洲沉积体系三、扇三角洲沉积体系一、曲流河三角洲沉积１．三角洲的亚环境和沉积特征２．三角洲的主要类型、沉积相组合、 沉积旋回及演化1.三角洲的亚环境和沉积特征两套术语（twosetsoftermsfordeltas）））Basedongradientofdeltaprofile（吉尔伯特，美
2、国，1885）:顶积层或三角洲台地topsetordeltaplatform前积层或三角洲斜坡foresetordeltaslope底积层或前三角洲bottomsetorprodelta推荐使用的术语Basedondelta-buildingprocesses:三角洲平原deltaplain上部高潮面以上下部低潮面以上三角洲前缘deltafront浪基面以上前三角洲prodelta浪基面以下水上三角洲水下三角洲所有三角洲都可以分为水上三角洲（三角洲平原：又分上部和下部）和水下三角洲（三角洲前缘和前三角洲）Phys
3、iographicandSedimentCharacteristicsofAlluvialDeltaicSystemsVariationsinsedimentinput,outflowvelocity,waveandcurrentenergy,andotherfactorsdiscussedcausethedepositionalfeaturesofdeltastoexhibitahighdegreeofvariabilityfromonedeltatoanother.Nevertheless,alldeltas
4、canbedividedintosubaerialandsubaqueouscomponents,eachofwhichcanbefurthersubdivided(Fig.10.15).Thesubaqueousdeltaplainliesseawardofthelowerdeltaicplainbelowlow-tidewaterlevelandischaracterizedbyrelativelyopenmarinefaunas.Theuppermostpartofthesubaqueousdelta,ly
5、ingatwaterdepthsdownto10morso,iscommonlycalledthedeltafront.（1）三角洲平原（DELTAPLAIN）Thesubaerialcomponentofdeltasisgenerallylargerthanthesubaqueouscomponentandisdividedintoanupperdeltaplain,whichlieslargelyabovehigh-tidelevel,andalowerdeltaplain,lyingbetweenlow-t
6、idemarkandtheupperlimitoftidalinfluence.Theupperdeltaplainiscommonlytheoldestpartofthedeltaandisdominatedbyfluvialprocesses.Thelowerdeltaplainisexposedduringlowtidebutiscoveredbywaterduringhightide.Thus,itissubjectedtobothfluvialandmarineprocesses.（1）三角洲平原（DE
7、LTAPLAIN）UpperDeltaPlainSedimentsTheupperdeltaplainliesmainlyabovetidalinfluenceandislittleaffectedbymarineprocesses,andthussimilartofluvialenvironmentsinmanyrespects,exceptthatareasofswamp,marshandlakeareusuallywidespreadandthatchannelsmaybifurcatedownstream
8、;Sedimentationontheupperdeltaisdominatedbydistributary-channelmigrationandassociatedfluvialsedimentationprocessessuchaschannelandpoint-bardeposition,overbankflooding,andcrevassingintolake
