【摘要】：西沙海槽盆地是南海北部陸坡西段的一個勘探程度較低的大型新生代深水沉積盆地�；谛虏杉母呔榷嗟赖卣鹳Y料并結(jié)合周邊地區(qū)地質(zhì)特征對盆地進行了層序地層分析,在研究區(qū)內(nèi)識別出8個地震反射界面,結(jié)合地震剖面振幅旋回性變化,將研究區(qū)新生代地層劃分了3個超層序和8個層序,并進一步論述了各層序的頂?shù)捉佑|關(guān)系、地震反射特征、地層厚度、層速度及砂巖含量等。在層序格架內(nèi)識別出5類典型的地震相:平行-亞平行相、楔狀發(fā)散相、前積相、雜亂相及水道充填相。在地震相劃分和沉積相分析的基礎上,通過對各層序沉積特征和沉積發(fā)育史的分析,認為始新世研究區(qū)呈現(xiàn)出陸相湖盆沉積體系特征;漸新世,盆地遭受海侵,研究區(qū)接受濱海相和淺海相沉積;早中新世,盆地中部沉積大規(guī)模半深海相沉積;中中新世末海平面出現(xiàn)下降,陸坡半深海環(huán)境的范圍有所減小,西沙海槽濁積水道的雛形形成;晚中新世之后,研究區(qū)進入穩(wěn)定的區(qū)域沉降階段,主要發(fā)育了一套半深海-深海相泥巖沉積。此外,由研究區(qū)南北緣隆起區(qū)提供物源在層序內(nèi)部還發(fā)育有近岸水下扇、三角洲、扇三角洲等沉積體,由地形高差控制作用在陡坡帶或斷層下降盤還形成了斜坡扇、濁積體。
[Abstract]:Xisha trough basin is a large Cenozoic deep-water sedimentary basin with low exploration degree in the western part of the northern continental slope of the South China Sea. Based on the newly acquired high-precision multi-channel seismic data and combined with the geological characteristics of the surrounding area, the sequence stratigraphy of the basin is analyzed. Eight seismic reflection interfaces are identified in the study area, and combined with the cyclic variation of the amplitude of the seismic section, the sequence stratigraphy of the basin is analyzed. The Cenozoic strata in the study area are divided into 3 supersequences and 8 sequences, and the top-bottom contact relationship, seismic reflection characteristics, stratigraphic thickness, bed velocity and sandstone content of each sequence are further discussed. Five types of typical seismic facies are identified in the sequence framework: parallel-sub-parallel facies, wedge-shaped divergence facies, pre-product facies, disordered facies and channel filling facies. On the basis of seismic facies division and sedimentary facies analysis, it is concluded that the Eocene study area has the characteristics of continental lacustrine basin sedimentary system through the analysis of the sedimentary characteristics and depositional development history of each sequence. In Oligocene, the basin suffered transgression, and the study area received coastal and shallow marine facies deposits, and early Miocene, large-scale semi-deep-sea facies deposits in the middle of the basin. The sea level decreased at the end of Miocene, the range of semi-deep sea environment on continental slope decreased, and the rudimentary form of turbidite channel in Xisha trough was formed. After the late Miocene, the study area entered a stable regional subsidence stage, mainly developed a set of semi-deep-sea-deep-sea facies mudstone deposits. In addition, the provenance from the upwelling area of the north and south margin of the study area also has inshore subaqueous fan, delta, fan delta and other sedimentary bodies within the sequence. The slope fan and turbidite body are also formed in the steep slope zone or fault descending plate controlled by the topographic height difference.
【作者單位】： 國土資源部海底礦產(chǎn)資源重點實驗室;中國地質(zhì)調(diào)查局廣州海洋地質(zhì)調(diào)查局;
【基金】：國家自然科學基金項目(91328205)
【分類號】：P618.13;P631.4;P736.2

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1 邱燕;吳進民;;南沙海域方安盆地地震相解釋及沉積相分析[J];南海地質(zhì)研究;1995年00期

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