Controls on Lateral Spreading Rates of Sustained Turbidity Currents

持续浊流横向扩散速率的控制

• 批准号: RGPIN-2019-04760
• 负责人: Steel, LinnElisabeth
• 金额: $ 1.82万
• 依托单位: Queen's University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=680401
• 关键词: Controls; Lateral; Spreading; Rates; Sustained

Turbidity currents are turbulent underflows capable of carving extensive submarine channel networks and depositing major accumulations of sediment in submarine fans. Turbidity currents are driven by gravity, and their excess density is provided by sediment held in suspension by fluid turbulence. They can be triggered through a variety of mechanisms, including re-suspension of sediment by earthquakes or over-steepened slopes, and by sediment-laden rivers in flood. Understanding how turbidites (deposits formed by turbidity currents) record turbidity current dynamics is critical when using turbidite successions in the rock record to infer paleogeography, paleoclimatic events, or paleoseismicity. Furthermore, their capacity to damage offshore infrastructure and equipment makes their prediction societally important. Finally, submarine fans serve as some of the world's most prolific hydrocarbon reservoirs and economic extraction of these hydrocarbons relies on accurate modelling of the extent and architecture of these deposits. *** Previous studies have focused on streamwise variability within turbidity currents. A natural continuation of this work is to consider planform evolution of submarine fan systems. Frontal and lateral spreading rates of turbidity currents provide a first-order control on the geometry of submarine fans, yet the variety of factors controlling turbidity current expansion remain poorly constrained. A series of experimental turbidity currents will be generated in an unconfined basin that is 5 m wide x 5 m long x 1 m deep to study the various inputs that affect turbidity current expansion, including interstitial fluid density, sediment concentration, and basin gradient. A second phase will consist of successions of turbidity currents to investigate how spreading rates are reflected in large-scale submarine fan architecture. Video cameras, time-lapse photography, velocity profiles, and a high-resolution laser scanner will be used to characterize turbidity currents. Further studies will examine the effects of interstitial fluid density on run-out distances of turbidity currents and the effects of basin geometry on the development of Taylor-Görtler vortices. Subsurface datasets and field compilations will be used to compare experimental results with natural turbidite systems. *** This work will support 2 PhD students, 3 MSc students, and 3 undergraduates. Results will build a more accurate understanding of the relationships between submarine fan geometry and gravity flow characteristics, which can ultimately be tied back to climatic or tectonic controls. Understanding the spreading behaviours of river-derived turbidity currents is critical to understanding the delivery, distribution, and burial of sediment, nutrients, and contaminants within basins. Furthermore, improving models of submarine fan morphology will lead to more accurate predictions of hydrocarbon reservoirs, resulting in more informed and economical recovery of hydrocarbons.

浊流是一种湍流底流，能够雕刻出广泛的海底水道网络，并在海底扇中沉积大量沉积物。湍流是由重力驱动的，其过剩密度由流体湍流悬浮的沉积物提供。它们可以通过各种机制触发，包括地震或过度陡峭的斜坡使沉积物重新悬浮，以及充满沉积物的河流泛滥。当利用岩石记录中的浊积岩序列来推断古地理、古气候事件或古地震活动时，了解浊积岩（浊流形成的沉积物）如何记录浊流动力学是至关重要的。此外，它们破坏近海基础设施和设备的能力使其预测具有重要的社会意义。最后，海底扇是世界上最多产的碳氢化合物储层，这些碳氢化合物的经济开采依赖于对这些矿床的范围和结构的准确建模。* 以前的研究集中在浊流内的流向变化。这项工作的自然延续是考虑海底扇系统的平面形态演变。浊流的前缘和侧向扩展速率对海底扇的几何形状提供了一阶控制，但控制浊流扩展的各种因素仍然没有得到很好的约束。一系列的实验浊流将在一个5米宽x5米长x1米深的无压盆地中产生，以研究影响浊流扩张的各种输入，包括间隙流体密度、沉积物浓度和盆地坡度。第二阶段将包括浊流的继承，以调查如何扩展率反映在大型海底扇结构。摄像机、延时摄影、流速剖面和高分辨率激光扫描仪将用于描述浊流的特征。进一步的研究将探讨间隙流体密度对浊流流出距离的影响，以及盆地几何形状对泰勒-格特勒涡旋发展的影响。地下数据集和现场汇编将用于比较实验结果与天然浊积岩系统。* 这项工作将支持2名博士生，3名硕士生和3名本科生。结果将建立一个更准确的理解之间的关系，海底扇的几何形状和重力流的特点，这最终可以追溯到气候或构造控制。了解河流产生的浊流的扩散行为对于了解流域内沉积物、营养物和污染物的输送、分布和埋藏至关重要。此外，改进海底扇形态模型将导致更准确地预测油气藏，从而更明智和经济地开采油气。