Grain-Size Controls On the Morphology and Internal Geometry of River-Dominated Deltas
Grain-Size Controls On the Morphology and Internal Geometry of River-Dominated Deltas
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DOI：
10.2110/jsr.2015.39
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发表时间：
2015-06
影响因子：
2
通讯作者：
A. Burpee;Rudy Slingerland;D. Edmonds;D. Parsons;J. Best;J. Cederberg;A. McGuffin;Rebecca L. Caldwell-Rebecca
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文献类型：
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作者：
A. Burpee;Rudy Slingerland;D. Edmonds;D. Parsons;J. Best;J. Cederberg;A. McGuffin;Rebecca L. Caldwell-Rebecca
三角洲的形态、相和地层的预测通常来自其相对的波浪、潮汐和河流能量，沉积物类型起较小的作用。在这里，我们测试的假设，所有其他因素相同，顶集的一个相对noncohesive，桑迪三角洲将有更多的活跃的分流，一个不那么多皱纹的海岸线形态，在其顶集的地形变化少，和较少的变化，在前积倾角方向比一个高度凝聚力，泥泞的三角洲。因此，其地层将具有更大的斜坡倾斜幅度和斜坡倾斜度，更大比例的河道相，以及比高粘性的泥质三角洲更少的褶皱砂体。采用二维水流泥沙模型-模型结果表明，砂为主的三角洲更扇形，而泥为主的三角洲更鸟脚在平面形状，因为砂为主的三角洲有更活跃的分流和较小的方差顶置高程，从而经历了更公平的沉积物分布到他们的周边。这导致砂质三角洲中河道相的比例更大，以及更均匀分布的斜坡倾斜方向、更陡的倾斜和更大的斜坡倾斜度。这些结论与从鹅河三角洲收集的数据是一致的，鹅河三角洲是一个粗粒度的扇三角洲，延伸到鹅湾，拉布拉多，加拿大。对白垩纪最后机会三角洲（位于美国犹他州埃默里附近的Ferron砂岩的一个单元）的Kf-1准层序组进行了重新解释，使用Ferron粒度数据、斜坡倾角数据、斜坡倾角和倾角方向的变化来后推三角洲的平面形状。Kf-1最后机会三角洲被预测在平面形态上更像是一个扇三角洲，而不是鸟足三角洲。
Predictions of a delta's morphology, facies, and stratigraphy are typically derived from its relative wave, tide, and river energies, with sediment type playing a lesser role. Here we test the hypothesis that, all other factors being equal, the topset of a relatively noncohesive, sandy delta will have more active distributaries, a less rugose shoreline morphology, less topographic variation in its topset, and less variability in foreset dip directions than a highly cohesive, muddy delta. As a consequence its stratigraphy will have greater clinoform dip magnitudes and clinoform concavity, a greater percentage of channel facies, and less rugose sand bodies than a highly cohesive, muddy delta. Nine self-formed deltas having different sediment grain sizes and critical shear stresses required for re-entrainment of mud are simulated using Deflt3D, a 2D flow and sediment-transport model. Model results indicate that sand-dominated deltas are more fan-shaped while mud-dominated deltas are more birdsfoot in planform, because the sand-dominated deltas have more active distributaries and a smaller variance of topset elevations, and thereby experience a more equitable distribution of sediment to their perimeters. This results in a larger proportion of channel facies in sand-dominated deltas, and more uniformly distributed clinoform dip directions, steeper dips, and greater clinoform concavity. These conclusions are consistent with data collected from the Goose River Delta, a coarse-grained fan delta prograding into Goose Bay, Labrador, Canada. A reinterpretation of the Kf-1 parasequence set of the Cretaceous Last Chance Delta, a unit of the Ferron Sandstone near Emery, Utah, USA uses Ferron grain-size data, clinoform-dip data, clinoform concavity, and variance of dip directions to hindcast the delta's planform. The Kf-1 Last Chance Delta is predicted to have been more like a fan delta in planform than a birdsfoot delta.