Low rates of lateral migration (centimetres to decimetres per year) combined with relatively high rates of vertical accretion (millimetres to centimetres per year) recorded in microtidal channels of the Venice Lagoon (Italy) give rise to point‐bar geometries and internal facies arrangements that differ substantially from widely accepted models of point‐bar sedimentary architecture. In this study, field data from the Venice Lagoon are combined with a three‐dimensional forward stratigraphic model, the ‘Point‐Bar Sedimentary Architecture Numerical Deduction’ (PB‐SAND), to predict the stratal geometries of point bars formed in aggradational settings. The PB‐SAND uses a combined geometric and stochastic modelling approach that can be constrained by field evidence. The model applied determines the geometry of four point bars generated by 9 to 11 m wide channels cutting through salt marshes. An iterative best‐fit modelling approach has been used to obtain multiple simulations for each case‐study, each of which fits the observations derived from the analysis of time‐series historical aerial photographs and 44 sedimentary cores. Results demonstrate how the geometry of the bars is determined by the development of two key stratal surfaces: the point‐bar brink and channel‐thalweg surfaces. These surfaces are defined by the progressive translation and vertical shift of the point‐bar brink (i.e. break of slope between bar top and bar slope) and the channel thalweg (i.e. deepest part of the channel) during bar evolution. The approach is used to: (i) reconstruct three‐dimensional point‐bar geometries; (ii) propose alternative reconstructions; (iii) provide insight to drive the acquisition of additional data to better constrain the proposed models; and (iv) provide insight into the mechanism of bar growth for slowly migrating channels in settings subject to relatively high rates of aggradation. This study highlights how interaction between styles of planform transformation and latero‐vertical shifts of meandering channels can determine the geometry of related sedimentary bodies.

中文翻译：

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确定潮汐点棒三维吸积几何形状的综合方法：来自威尼斯泻湖的示例

在威尼斯泻湖（意大利）的微潮水道中记录的低横向迁移率（每年厘米到分米）与相对较高的垂直吸积率（每年毫米到厘米）相结合，形成了点坝几何形状和内部相排列与广泛接受的点坝沉积结构模型有很大不同。在这项研究中，来自威尼斯泻湖的现场数据与三维正向地层模型“点-坝沉积结构数值演绎”（PB-SAND）相结合，以预测在堆积环境中形成的点坝的地层几何形状。PB-SAND 使用可以受现场证据约束的组合几何和随机建模方法。所应用的模型确定了由 9 至 11 m 宽的通道穿过盐沼产生的四个点棒的几何形状。使用迭代最佳拟合建模方法为每个案例研究获得多个模拟，每个模拟都符合从时间序列历史航拍照片和 44 个沉积岩心分析中得出的观察结果。结果证明了钢筋的几何形状是如何由两个关键地层表面的发展决定的：点-钢筋边缘和通道-thalweg 表面。这些表面由钢筋演化过程中点-钢筋边缘（即钢筋顶部和钢筋坡度之间的坡度的中断）和通道thalweg（即通道的最深部分）的渐进平移和垂直移动定义。该方法用于：（i）重建三维点杆几何结构；(ii) 提出替代重建方案；(iii) 提供洞察力以推动获取额外数据，以更好地约束提议的模型；(iv) 深入了解在受相对较高聚集率影响的环境中缓慢迁移通道的条形生长机制。这项研究强调了平面变换样式和蜿蜒通道的横向垂直移动之间的相互作用如何确定相关沉积体的几何形状。