半地堑裂谷盆地蜿蜒河流序列沉积构造的三维正向地层建模,Basin Research

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半地堑裂谷盆地蜿蜒河流序列沉积构造的三维正向地层建模
Basin Research ( IF 2.8 ) Pub Date : 2019-06-06 , DOI: 10.1111/bre.12367
Na Yan ₁ , Luca Colombera ₁ , Nigel P. Mountney ₁

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[摘要] 在裂谷盆地的沉积充填物中，曲流河沉积物的空间组织变化很大，这取决于断层传播和沉降的差异速率如何与自生过程相互作用以驱动河流通道带位置和迁移速率的变化，撕脱频率和曲折切断的机制。这组过程从根本上影响了累积序列的堆叠模式。在这种构造活跃的环境中，对蜿蜒河流沉积物的时空演化和内部结构的定量预测仍然有限。一个数值正向地层模型——点杆沉积结构数值推演（PB-SAND）——被用于检查不同的沉降速率和由此产生的河道带迁移之间的关系，在活动的、断层边界的半地堑中达到撕脱和通道沉积堆积。该模型用于重建和预测河流曲流的复杂形态动力学、它们生成的河道带以及相关的岩相分布，这些岩相分布在裂谷环境中作为非均质河流序列积累，受地震图像和露头序列数据的约束。3D 建模输出用于探索不同时空尺度的沉积非均质性。结果表明，如何将易出砂地质体的连通性量化为沉降速率的函数，沉降速率本身沿盆地边界断层和远离盆地边界断层均减小。特别是，结果突出了在垂直和平行于盆地轴的方向上观察到的易出砂地质体的大小和连通性的空间变异性，这是作为住宿生成速率和断层速率的空间和时间变化之间相互作用的函数而出现的。影响河流形态动力学的变化。例如，这些结果对油气勘探和地下水含水层评估具有重要意义。半地堑中河流砂体的预期最大连通性主要取决于沉降频率和沉降速率、盆地传播方式、河道带迁移速率、剥蚀频率和比例和空间之间的复杂相互作用。易出砂通道和坝状沉积物的分布。在以河流为主导的大陆环境中演化的半地堑盆地示意图。]

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Three‐Dimensional Forward Stratigraphic Modelling of the Sedimentary Architecture of Meandering‐River Successions in Evolving Half‐Graben Rift Basins

[Abstract The spatial organisation of meandering‐river deposits varies greatly within the sedimentary fills of rift basins, depending on how differential rates of fault propagation and subsidence interplay with autogenic processes to drive changes in fluvial channel‐belt position and rate of migration, avulsion frequency and mechanisms of meander‐bend cut off. This set of processes fundamentally influences stacking patterns of the accumulated successions. Quantitative predictions of the spatio‐temporal evolution and internal architecture of meandering fluvial deposits in such tectonically active settings remain limited. A numerical forward stratigraphic model—the Point‐Bar Sedimentary Architecture Numerical Deduction (PB‐SAND)—is applied to examine relationships between differential rates of subsidence and resultant fluvial channel‐belt migration, reach avulsion and channel‐deposit stacking in active, fault‐bounded half‐grabens. The model is used to reconstruct and predict the complex morphodynamics of fluvial meanders, their generated channel belts, and the associated lithofacies distributions that accumulate as heterogeneous fluvial successions in rift settings, constrained by data from seismic images and outcrop successions. The 3D modelling outputs are used to explore sedimentary heterogeneity at various spatio‐temporal scales. Results show how the connectivity of sand‐prone geobodies can be quantified as a function of subsidence rate, which itself decreases both along and away from the basin‐bounding fault. In particular, results highlight the spatial variability in the size and connectedness of sand‐prone geobodies that is seen in directions perpendicular and parallel to the basin axis, and that arises as a function of the interaction between spatial and temporal variations in rates of accommodation generation and fault‐influenced changes in river morphodynamics. The results have applied significance, for example, to both hydrocarbon exploration and assessment of groundwater aquifers. The expected greatest connectivity of fluvial sandbody in a half‐graben is primarily determined by the complex interplay between the frequency and rate of subsidence, the style of basin propagation, the rates of migration of channel belts, the frequency of avulsion and the proportion and spatial distribution of variably sand‐prone channel and bar deposits., Schematic diagram of an evolving half‐graben basin in a fluvial‐dominated continental setting. ]

更新日期：2019-06-06

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