Coastal barriers provide sheltered, low‐energy settings for fine‐grained sediment deposition and retention, although the process of back‐barrier infilling and how tidal‐channel connectivity impacts this process is not well‐understood. Understanding how back‐barrier environments infill and evolve is necessary to predict how they will respond to future changes in sea‐level and sediment supply. With this motivation, in situ observations and sedimentary signatures from an Amazonian tidal‐channel system are interpreted to create a conceptual model of morphological evolution in a macrotidal back‐barrier environment that is rich in fine‐grained sediment, vegetated by mangroves and incised by tidal channels with multiple outlets. Results indicate that within a high‐connectivity back‐barrier channel, tidal processes dominate sedimentation and morphological development. Sediment cores (<60 cm) exhibited millimetre‐scale tidalites composed of sand and mud. High‐connectivity channels allow tidal propagation from multiple inlets, and in this case, the converging flood waves promote delivery of sediment fluxing through the system to the mangrove flats in the convergence zone. Sediment preferentially deposits in regions with adequate accommodation space and dense vegetation, and in these zones, sediment grain size is slightly finer than that transiting through the system. The greatest sediment‐accumulation rates (3 to 4 cm yr⁻¹), calculated from steady‐state ²¹⁰Pb profiles, were found in the convergence zone near the mangrove‐channel edge. As tidal flats aggrade vertically and prograde into the channels, accommodation space diminishes. In effect, the channel’s narrowest stretch is expected to migrate along the path of net‐sediment flux towards regions with more accommodation space until it reaches the tidal‐convergence zone. The location of recent preferential infilling is evidenced by relatively rapid sediment‐accumulation rates, finer sediment and significant clustering of small secondary tidal channels. These findings shed light on how sediment transported through vegetated back‐barrier environments is ultimately preserved and how evidence preserved in surface morphology and the geological record can be interpreted.

中文翻译：

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巨潮逆向屏障环境的形态演化：亚马逊海岸

沿海屏障为细颗粒状沉积物的沉积和滞留提供了低能量的掩护环境，尽管对反向屏障的填充过程以及潮汐通道的连通性如何影响这一过程的理解尚不清楚。必须了解后屏障环境如何填充和演化，以预测它们将如何应对未来海平面和沉积物供应的变化。有了这种动力，就地解释了来自亚马逊潮汐通道系统的观测资料和沉积特征，从而在大潮汐后壁屏障环境中建立了形态演化的概念模型，该环境富含细粒度的沉积物，被红树林植被并且被具有多个出口的潮汐通道切割。结果表明，在高连通性反向屏障通道中，潮汐过程主导着沉积和形态发育。沉积物芯（<60厘米）表现出由沙子和泥浆组成的毫米级潮汐岩。高连通性的通道允许潮汐从多个入口传播，在这种情况下，会聚的洪水波促进沉积物通量通过系统输送到会聚区的红树林。沉积物优先沉积在有足够居住空间和茂密植被的地区，在这些区域中，沉积物的颗粒尺寸比通过系统的沉积物的颗粒尺寸稍细。最大的沉积物积累速率（3至4 cm年）^-1），由稳态²¹⁰计算得出在红树林通道边缘附近的收敛带发现了铅剖面。随着潮汐带垂直地上升并进入河道，居住空间逐渐减少。实际上，该河道最窄的延伸预计将沿着净泥沙通量的路径向具有更多容纳空间的区域迁移，直至到达潮汐收敛区。相对较快的沉积物堆积速度，较细的沉积物和小的次潮汐通道的明显聚集证明了最近优先填充的位置。这些发现揭示了如何最终保留通过植被后屏障环境运输的沉积物以及如何解释表面形态和地质记录中保存的证据。