The characterization of ancient fluvial-channel bars informs predictions of sedimentary facies distribution, and hence they are critical for interpreting river morphodynamics through time. Within active fluvial channels, sediment storage occurs along the banks or along their axial portion, generating bank-attached or mid-channel bars, respectively. This study introduces the angle of flow divergence (Δf), measured as the angle between the azimuths of bar accretionary slopes and local dune migration, and quantitatively explores its distribution in 103 channel reaches that have a sandy bed load and clear water. This dataset includes both mid-channel and bank-attached bars from low-variable peak discharge rivers of Russia and Brazil. Remotely sensed evidence shows that dune migration transverse to the dip azimuth of bar slopes (Δf 90–110°) occurs both in mid-channel and bank-attached bars, contradicting the long-standing tenet that palaeoflows nearly orthogonal to the dip azimuth of large-scale inclined strata are indicative of sinuous, single-thread palaeochannels. Only Δf values significantly higher (>140°) or lower (<60°) than 90° discriminate mid-channel and bank-attached fluvial bars. Comparisons between Δf values and bar-accretionary styles suggest that mid-channel bars formed by high-peak and low-peak variable discharge rivers tend to preserve axially and laterally accreting deposits, respectively. Nearly orthogonal divergence angles are found in bank-attached bars irrespective of peak-discharge variability. While stressing that analyses akin to the one presented here are to be complemented with additional sedimentological information from high-quality outcrops, this study proposes a new, quantitative, approach to better distinguish fluvial bars, and hence possibly the planform pattern of associated channel bodies, from sedimentary successions. In particular, the data show that a reliable distinction between mid-channel and bank-attached bars should be based on comprehensive palaeocurrent and architectural information from various portions of preserved bar bodies, and that inferences based on limited datasets should be considered with caution.

中文翻译：

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通过流量发散区分河中和河岸附着的河流坝：对地层记录解释的影响

古代河流河道坝的特征为沉积相分布的预测提供信息，因此它们对于解释河流形态动力学随时间变化至关重要。在活跃的河流河道内，沉积物沿河岸或沿河岸的轴向部分发生，分别产生与河岸相连或河道中部的坝。本研究介绍了流动发散角（Δf)，以沙坝增生坡度与局部沙丘迁移的方位角之间的夹角来衡量，并定量探讨其在 103 个沙床荷载和清水河段中的分布。该数据集包括来自俄罗斯和巴西的低变量峰值流量河流的中间河道和岸边的酒吧。遥感证据表明，沙丘迁移横向于坝坡倾角 ( Δf 90–110°) 发生在河道中部和附着岸坝，这与古流几乎与大坝坡倾角正交的长期原则相矛盾。 - 尺度倾斜的地层表明蜿蜒的单线古河道。只有Δf值显着高于 (>140°) 或低于 (<60°) 比 90° 区分中间河道和河岸附着的河流酒吧。Δf之间的比较值和条形增生样式表明，由高峰和低峰可变流量河流形成的中通道坝倾向于分别保留轴向和横向增生的沉积物。无论峰值流量变化如何，在岸边的钢筋中都发现了几乎正交的发散角。在强调类似于此处介绍的分析时，需要补充来自高质量露头的额外沉积学信息，本研究提出了一种新的、定量的方法来更好地区分河流条带，从而可能区分相关河道体的平面模式，来自沉积层序。特别是，