【作者】 刘聪；

【导师】 樊太亮；

【作者基本信息】 中国地质大学（北京） ， 矿产普查与勘探， 2011， 博士

【摘要】 澳大利亚西北大陆架北卡那封盆地上渐新统至中中新统以碳酸盐岩沉积为主偶夹碎屑岩,其地层整体特点从东南陆架向西北斜坡前积叠置。因此,该前积斜坡地层成为本论文研究的重点。利用三维地震资料、测井、岩心、古生物及古海深等资料,识别6个三级层序界面,划分5个三级层序(SQ1-SQ5)。在建立层序格架的基础上,分析了层序的内部反射特征、外部几何形态及特殊地质现象的发育,研究各层序的沉积中心迁移规律,其沉积中心主要沿北西方向迁移。以不同学者对碳酸盐岩台地沉积相模式为指导,分析本工区钻测井地震等资料,总结了北卡那封盆地目的层沉积相模式:从南东陆地向北西盆地依次为碳酸盐台地缓坡相、斜坡相至浅海盆地相。其中碳酸盐台地缓坡相又被分为内缓坡亚相、中缓坡亚相及外缓坡亚相;斜坡相被分为前缘斜坡亚相和斜坡脚亚相。利用钻井资料建立了沉积相纵向演变序列,根据地震相各参数的变化分析了沉积相的横向展布规律,并进而恢复了不同层序沉积相平面展布。依据Vail等(1977)利用滨岸上超变化制作相对海平面变化曲线的方法,编制了相对海平面变化曲线。将该海平面相对变化曲线与Moss等(2004)利用古生物资料制作古海深曲线对比,表现出良好的一致性。从相对海平面变化曲线看出,层序SQ2和SQ3下部形成于海平面相对下降期,层序SQ3上部和SQ4形成于海平面相对上升期。在海平面相对下降期,层序SQ2内发育的小型沟谷可能是压实作用下流体溢出侵蚀形成的;层序界面SB3和上覆地层在外大陆架处发育丘形体,该丘形体代表生物建隆。SQ4虽然发育于海平面相对上升期,但其内部包括多个次级海平面升降旋回。层序界面SB4位于海平面相对下降期,发育台阶状不连续面,被认为是海平面或附近的波浪侵蚀作用形成的被埋藏并被保存的海岸悬崖。SQ5层序发育于中中新世-晚中新世时期,为气候干燥期,海平面相对较低、古海深度较浅,层序内部发育的下切侵蚀现象可能是沿前积方向的重力流和沿走向的等深环流共同作用形成的。更多还原

【Abstract】 The strata of late Oligocene to mid Miocene are dominated by carbonate sediment and interbeded clastic sediment in Northern Carnavon Basin, North West of Australia. The character of the strata is progradational clinoform sediment from southeast to northwest. The progradational clinoform sediment is considered as a very good model to investigate the relationship between sedimentary system and relative sea level change.Based on thred dimensional seismic data, well log data, well core data, paleontology and paleobathemetry, we recognized 6 third-order sequence boundaries (5 third order sequences: SQ1-SQ5) and 21 four-order sequence boundaries. We analyzed the the character of each sequence, including inner reflection, geometry and special geological phenomena. Then we generated TWT isopach maps of each sequence and depict the depocenter of each sequence. All sequences exhibit strike-oriented depocenters prograding northwest.We apply seismic attributes extraction techniques to trace the boundaries of different lithology and facies, and also use seismic data and well data to construct the sedimentary facies distribution maps. From southeast to northwest, sediment facies of objective area are divided into carbonate platform ramp face, carbonate platform margin face and shallow sea basin face. Carbonate platform ramp face is divided into inner ramp sub-face, middle ramp sub-face and outer ramp sub-face. Carbonate platform margin face is divided into front of clinoform sub-face and toe of clinoform sub-face.According to the method of making relative sea level change chart from Vail et al. (1977), we chose one seismic profile to build sea level relative chage curve. The chart shows relative sea level is low in SQ2 and the lower part of SQ3, but high in the higher part of SQ3 and SQ4. Then we compare this relative sea level change curve to the paleobathymetry of G7. The trend of these two curves mathced generally well except some parta. The relative sea level change chart can help us to understand the mechanism of developing of geological phenomena on sequence boundaries.During the falling period of relative sea level, small gullies developed during SQ2. We propose that water derived from compaction can cause such features. The mounds grew on SB3 and overlying strata may represent biogenic buildups. Although SQ4 developed during the rising period of relative sea level, this sequence had several short term relative rise and fall cycles. From the chart, we observed that SB4 located in relative sea level fall period. The step-like discontinuity on SB4 stands for a rare example of a buried and preserved sea cliff, generated by wave erosion at ambient sea level. SQ5 was in the period of relative sea level fall and shallow paleobethmetry. We suggest that incisions in SQ5 may indicate two geological effects caused this phenomenon: gravity flow along progradation direction and contour current along strike orientation.更多还原