Interactions between footwall-, hangingwalland axial-derived depositional systems make syn-rift stratigraphic architecture difficult to predict, and preservation of net-erosional source landscapes is limited. Distinguishing between deposits derived from fault-scarp degradation (consequent systems) and those derived from long-lived catchments beyond the fault block crest (antecedent systems) is also challenging, but important for hydrocarbon reservoir prospecting. We undertake geometric and volumetric analysis of a fault-scarp degradation complex and adjacent hangingwall-fill associated with the Thebe-2 fault block on the Exmouth Plateau, NW Shelf, offshore Australia, using high resolution 3D seismic data. Vertical and headward erosion of the complex and fault throw are measured. Seismicstratigraphic and seismic facies mapping allow us to constrain the spatial and architectural variability of depositional systems in the hangingwall. Footwall-derived systems interacted with hangingwalland Footwall degradation and syn-rift architecture Barrett et al. (2020) 2 axial-derived systems, through diversion around topography, interfingering, or successive onlap. We calculate the volume of footwall-sourced hangingwall fans (VHW) for nine quadrants along the fault block, and compare this to the volume of material eroded from the immediately up-dip fault-scarp (VFW). This analysis highlights areas of sediment bypass (VFW>VHW) and areas fed by sediment sources beyond the degraded fault scarp (VHW>VFW). Exposure of the border fault footwall and adjacent fault terraces produced small catchments located beyond the fault block crest that fed the hangingwall basin. One source persisted throughout the main syn-rift episode, and its location coincided with: (i) an intrabasin topographic high; (ii) a local fault throw minimum; (iii) increased vertical and headward erosion within the fault-scarp degradation complex; and (iv) sustained clinoform development in the immediate hangingwall. Our novel quantitative volumetric approach to identify through-going sediment input points could be applied to other rift basin-fills. We highlight implications for hydrocarbon exploration and emphasise the need to incorporate interaction of multiple sediment sources and their resultant architecture in tectono-stratigraphic models for rift basins.

中文翻译：

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澳大利亚近海西北大陆架埃克斯茅斯高原下盘陡坡退化复合体和同裂谷地层结构的定量分析

下盘、上盘和轴源沉积系统之间的相互作用使得同裂谷地层结构难以预测，并且净侵蚀源景观的保存有限。区分源自断层陡坡退化（后续系统）的沉积物和源自断块顶部以外的长寿命集水区（前驱系统）的沉积物也具有挑战性，但对油气藏勘探很重要。我们使用高分辨率 3D 地震数据对与澳大利亚近海西北大陆架埃克斯茅斯高原上的 Thebe-2 断层块相关的断层 - 陡坡退化复合体和相邻的上盘填充物进行几何和体积分析。测量复合体和断层的垂直和向前侵蚀。地震地层和地震相绘图使我们能够限制上墙沉积系统的空间和结构变化。下盘衍生系统与上盘和下盘退化和同步裂谷结构相互作用。 Barrett 等人。(2020) 2 个轴向衍生系统，通过围绕地形的改道、相互交叉或连续的重叠。我们计算了沿断块的九个象限的下盘源上盘扇 (VHW) 的体积，并将其与直接上倾断层陡崖 (VFW) 侵蚀的物质体积进行了比较。该分析突出显示了沉积物旁路区域 (VFW>VHW) 和退化断层陡坡以外的沉积物来源区域 (VHW>VFW)。边界断层下盘和相邻断层阶地的暴露产生了位于为上盘盆地提供水源的断块顶部之外的小集水区。一个源在整个主要同裂谷事件中持续存在，其位置与：（i）盆地内地形高；(ii) 局部故障转移最小值；(iii) 断层-陡崖退化复合体中的垂直和向前侵蚀增加；(iv) 在紧邻的悬壁中持续的斜面发育。我们用于识别贯穿沉积物输入点的新颖定量体积方法可应用于其他裂谷盆地填充物。我们强调了对油气勘探的影响，并强调需要在裂谷盆地的构造地层模型中纳入多种沉积物来源及其由此产生的结构的相互作用。