Abstract We examine the nature and number of event beds preserved in heterolithic prodelta and delta-front strata in five proximal-accumulation-dominated (PAD) North American delta systems including the Quaternary Gulf of Mexico and the Late Cretaceous Western Interior Seaway. We also explore the continuum between PAD, more distal deposits of mud belts, and thicker subaqueous-delta-clinoforms (SDC). Sediment accumulation rates in modern PAD and SDC systems are commonly on the order of several to severaltens of centimeters per year. They also show that several event beds may be created annually, with preservation depending on supply and reworking. The PAD heterolithics commonly comprise interbedded sand, silt and clay. These show normal and inverse grading and Bouma sequences, indicating deposition from turbidity currents and hyperpycnal flows that are interpreted as the products of river plumes generated during flood episodes. Re-equilibrated Rosselia socialis in stacked delta front turbidite bedsets in the Cretaceous examples show that floods may occur as a cluster of events over several months. Shelf areas adjacent to river mouths may experience high rates of sediment delivery from rivers, but oceanographic processes are instrumental in moving much of the silt and clay farther along the shelf. Direct, hyperpycnal delivery from a river mouth on a low gradient shelf (i.e., typically

中文翻译：

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三角洲中的生物扰动、沉积速率和洪水事件的保存

摘要 我们研究了包括墨西哥第四纪湾和晚白垩世西部内陆海道在内的五个近端堆积主导 (PAD) 北美三角洲系统中异石前三角洲和三角洲前缘地层中保存的事件层的性质和数量。我们还探索了 PAD、更远的泥带沉积物和更厚的水下三角洲斜岩 (SDC) 之间的连续体。现代 PAD 和 SDC 系统中的沉积物积累率通常在每年几厘米到几十厘米的数量级。他们还表明，每年可能会创建几个活动床，保存取决于供应和返工。PAD 异质岩通常包括夹层砂、粉砂和粘土。这些显示正常和反向分级和 Bouma 序列，表明来自浊流和超重流的沉积，被解释为洪水期间产生的河流羽流的产物。在白垩纪的例子中，在堆积的三角洲前缘浊积岩床中重新平衡的 Rosselia socialis 表明，洪水可能会在几个月内以一系列事件的形式发生。与河口相邻的陆架区域可能会经历来自河流的高速沉积物输送，但海洋学过程有助于将大部分淤泥和粘土沿着陆架移动得更远。从低梯度陆架上的河口直接、高密度输送（即，通常 在白垩纪的例子中，在堆积的三角洲前缘浊积岩床中重新平衡的 Rosselia socialis 表明，洪水可能会在几个月内以一系列事件的形式发生。与河口相邻的陆架区域可能会经历来自河流的高速沉积物输送，但海洋学过程有助于将大部分淤泥和粘土沿着陆架移动得更远。从低梯度陆架上的河口直接、高密度输送（即，通常 在白垩纪的例子中，在堆积的三角洲前缘浊积岩床中重新平衡的 Rosselia socialis 表明，洪水可能会在几个月内作为一系列事件发生。与河口相邻的陆架区域可能会经历来自河流的高速沉积物输送，但海洋学过程有助于将大部分淤泥和粘土沿着陆架移动得更远。从低梯度陆架上的河口直接、高密度输送（即，通常