Processes and products of turbidity currents entering soft muddy substrates
Processes and products of turbidity currents entering soft muddy substrates
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DOI：
10.1130/g35296.1
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发表时间：
2014-05
期刊：
影响因子：
5.8
通讯作者：
J. Baas;Rafael Manica;Eduardo Puhl;I. Verhagen;A. L. Borges
中科院分区：
文献类型：
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作者：
J. Baas;Rafael Manica;Eduardo Puhl;I. Verhagen;A. L. Borges
新的实验室实验表明，无粘性浊流能够进入粘性软泥底质，而不会失去形状。这些床内流是由床剪切应力超过床内聚强度和流动密度超过床密度驱动的。水流产生独特的浊积岩，内部有泥层、混合的粘性-非粘性-粘性沉积层以及火焰和荷载结构。提出了一种层内浊积岩沉积模式，从底部到顶部包括：I1“含砂泥，具有冲刷基底、分散泥和泥碎屑; I2”来自旋转流层内部分的泥砂; I3“具有斑点外观的桑迪泥;以及I4”来自流动层上部分的贫泥砂。完整的I1 → I4浊积岩被推断为自然界中占主导地位的地方，水流与河床混合，形成深层侵蚀冲刷，充满变形或混乱的砂泥混合物。进一步向下流动，底部缺失的I2 → I4和I4序列表示逐渐减速，侵蚀力丧失，以及床内流动的终止
New laboratory experiments reveal that cohesionless turbidity currents are able to enter cohesive soft muddy substrates without losing their shape. These intrabed currents are driven by bed shear stress exceeding bed cohesive strength, and by flow density exceeding bed den - sity. The flows produce unique turbidites with internal mud layers, mixed cohesive-nonco - hesive sediment layers, and flame and load structures. A depositional model for intrabed (I) turbidites is proposed, comprising, from base to top: I1�sand-bearing mud, with a scoured base, dispersed mud, and mud clasts; I2�muddy sand from the intrabed portion of the tur - bidity current; I3�sandy mud with a speckled appearance; and I4�mud-poor sand from the suprabed portion of the flow. Complete I1�I4 turbidites are inferred to dominate loca - tions in nature where the currents mix with the bed and deep erosional scours form, filled with deformed or chaotic sand-mud mixtures. Further downflow, base-missing I2�I4 and I4 sequences signify gradual deceleration, loss of erosivity, and termination of intrabed flow