Most sequence stratigraphic models are based on the premise that relative changes in sea level (RSL) control stacking patterns in continental-margin settings. An alternative hypothesis, however, is that upstream factors, notably variations in relative water discharge (RQW) or the ratio of water to sediment discharge can influence or control stratal stacking patterns in fluvial systems. Sequence boundaries of RQW-driven systems differ from those driven by base-level fluctuations in that: 1) the depth of incision increases updip, and 2) rates of erosion are spatially uniform, leading to the formation of widespread, planar sequence boundaries. This paper presents an architectural and stratigraphic analysis of the well-exposed Masuk Formation of the Henry Mountains Syncline in southern Utah, an Upper Cretaceous coastal-plain fluvial succession that is interpreted to have been influenced significantly by RQW. Six lithofacies are recognized, three (Facies 1–3) recording floodbasin, mire, and (in one short interval) estuarine environments, and three (Facies 4–6) record different kinds of channel fills on a coastal alluvial plain. Seven major composite channel bodies (Facies 4–6), separated by intervals of non-channel deposits (Facies 1–3), are recognized in the stratigraphic interval. Composite channel bodies display planar, sheet-like geometry and are laterally continuous to a significantly greater extent (> 10 km) than would be expected from purely autogenic channel-belt construction. Together, these intervals record a series of high-frequency sequences, formed along the western margin of the Western Interior Seaway. In each individual sequence is a repetitive facies succession from a basal chaotic sandstone with admixed mudrock and sandstone transitioning upward to a more organized cross-bedded and stratified sandstone. This is interpreted to record cyclical changes from a peaked (flashy) discharge regime to a more normal runoff regime. Paleoflow data indicate a dominance of transverse (eastward-directed) dispersal early in the accumulation of the Masuk Formation, shifting to a pattern of greater axial (northward) dispersal over time. The RQW signal is strong in the lower part of the formation, decreasing upward. This suggests that the relatively short-headed streams draining from the rising Sevier fold–thrust belt were strongly influenced by climatic cyclicity, whereas more distally sourced systems were not. This study provides new insights into the architecture and stacking patterns of coastal-plain fluvial successions, emphasizing the plausible role that climate can play in shaping alluvial architecture in the rock record.

中文翻译：

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美国犹他州上白垩统Masuk组的沿海平原河流构造和高频叠加模式分析：气候驱动的周期性？

大多数层序地层学模型都基于这样的前提，即海平面（RSL）的相对变化控制着大陆边缘环境中的堆积模式。但是，另一种假设是上游因素，尤其是相对水流量（RQW）的变化或水与沉积物流量的比值会影响或控制河流系统中的地层堆积模式。RQW驱动的系统的序列边界与由基本水平波动驱动的序列边界的不同之处在于：1）切口的深度增加了上冲，并且2）侵蚀速率在空间上是均匀的，从而导致形成了广泛的平面序列边界。本文对犹他州南部亨利山脉向斜线中暴露良好的Masuk组进行了建筑和地层分析，上白垩统沿海平原河床演替被认为受RQW影响很大。识别出6个岩相，其中3个（相1–3）记录了流域，泥潭和（短时间内）河口环境，还有3个（相4-6）记录了沿海冲积平原上不同类型的河道填充物。在地层间隔中可以识别出七个主要的复合通道体（相4-6），它们之间以非通道沉积物的间隔（相1-3）分隔。复合通道主体显示出平面的片状几何形状，并且横向连续程度比纯自生通道带构造要大得多（> 10 km）。这些间隔一起记录了一系列沿西部内部航道西缘形成的高频序列。在每个单独的层序中，都是基底混叠砂岩与混合泥岩和砂岩向上过渡过渡到更加有序的层状和分层砂岩的重复相演替。这被解释为记录从峰值（闪烁）排放状态到更正常径流状态的周期性变化。古流数据表明，在Masuk组的堆积早期，横向（向东）扩散占主导地位，随时间推移向轴向（向北）扩散方向转移。RQW信号在地层下部较强，向上减小。这表明从上升的Sevier褶皱冲断带中排出的相对短头的水流受到气候周期性的强烈影响，而来自远端的系统则不受此影响。