Stratigraphic Evolution of Fine-Grained Submarine Fan Systems, Tanqua Depocenter, Karoo Basin, South Africa
Stratigraphic Evolution of Fine-Grained Submarine Fan Systems, Tanqua Depocenter, Karoo Basin, South Africa
复制标题
细粒度海底扇系统的地层演化，南非卡鲁盆地 Tanqua Depocenter
DOI：
10.2110/jsr.2006.03
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发表时间：
2006
影响因子：
2
通讯作者：
S. Luthi
中科院分区：
文献类型：
--
作者：
D. Hodgson;S. Flint;D. Hodgetts;N. Drinkwater;E. Johannessen;S. Luthi
相关露头和新获得的岩心和电缆测井、广泛的古水流数据以及精确绘制的表面相结合，使南非卡鲁盆地西南部坦夸沉积中心的四个二叠纪细粒海底扇系统（扇1-4）的地层演化形成了一个通用模型。此外，这些数据揭示了微妙的海底地形对扇系统边界、内部相结构和古水流方向的影响。此外，现在已知单个扇系统的内部地层比最初认为的要复杂。绘制高频扇内单元揭示了每个海底扇共同的沉积-加积-退积堆积模式，这使得可以预测岩相和建筑元素的地理和地层分布。盆地向内的主要馈线系统，扇轴占主导地位的建筑片浊积岩与离散区的高汞齐化在adhedational和加积阶段，而孤立的通道形式，削减薄层浊积岩更常见的退积阶段。这种变化被解释为是由于当地增加较低的坡度，通过沉积物淤积增加潜在的通道撕脱和发展的八字瓣在减少沉积物供应。在此基础上，将海侵、加积和退积阶段分别划分为一个五级层序的早、中、晚期低位体系域。每个相位都由更高频率（六阶）的序列构成，因此每个扇形都是一个复合序列。单个扇体整体上向盆地向陆地的步进意味着在任何盆底扇系统中向下倾斜，保存的最低砂岩逐渐变年轻，而最上面的砂岩逐渐变老。这种堆叠模式对储层和密封几何形状进行了重要的可预测控制。这项研究有助于开发细粒海底扇的形成、生长和废弃的预测模型，以及岩相和建筑元素在空间和时间上的分布。
Abstract The integration of correlated outcrop and newly acquired core and wireline logs, extensive paleocurrent data, and accurately mapped surfaces has enabled a common model of the stratigraphic evolution to be developed of four Permian fine-grained submarine fan systems (Fans 1–4) from the Tanqua depocenter, SW Karoo Basin, South Africa. Additionally, this data has revealed the influence of subtle seabed topography on the fan systems' boundaries, internal facies architecture, and paleocurrent directions. Furthermore, the internal stratigraphy of individual fan systems are now known to be more complex than first believed. Mapping high-frequency intrafan units reveals a progradational–aggradational–retrogradational stacking pattern common to each submarine fan, which allows the geographic and stratigraphic distribution of lithofacies and architectural elements to be predicted. Basinward of the main feeder system, fan axes are dominated architecturally by sheet turbidites with discrete zones of high amalgamation during progradational and aggradational phases, whereas isolated channel forms that cut thin-bedded turbidites are more common in the retrogradational phase. This change is interpreted to be due to local increase in the lower slope gradient through sediment aggradation increasing the potential for channel avulsion and the development of splay lobes during decreasing sediment supply. The progradational, aggradational, and retrogradational phases are assigned to the early, middle, and late lowstand systems tract of a fifth-order sequence respectively. Each phase is built of higher-frequency (sixth-order) sequences so that each fan is a composite sequence. The overall basinward-to-landward stepping of the individual fans means that moving down dip in any basin-floor fan system, the lowermost sandstone preserved is progressively younger, whilst the uppermost sandstone is progressively older. This stacking pattern imparts an important predictable control on reservoir and seal geometries. This study aids the development of predictive models for fine-grained submarine fan initiation, growth, and abandonment, and lithofacies and architectural element distributions in space and time.