EAGER: Single-grain Optical Dating of Debris-flow Fans

泥石流是大量移动的沉积物，发生在世界各地，形成景观，并在历史上造成相当大的破坏。关于它们的史前频率的知识可以通过使用各种测年方法来获得（例如，树木年代学或碳-14），但考虑到泥石流的年龄、复杂性和背景，这些通常是不可能的。本提案将测试替代测年工具-单颗粒石英（SGQ）发光测年法的适用性。 石英的单颗粒和多颗粒光学测年是一项经过验证的技术，但从未尝试过用于泥石流。准确的光学测年取决于通过暴露于太阳辐射至少数十秒来重置时钟。 泥石流发生的湍流和快速过程可能并不总是允许夹带的石英颗粒有足够的时间进行这种暴露。选择了两个地点进行这项试验。 1983年，里诺附近发生了一次泥石流，持续时间短（8到10分钟），空间范围小（0.57平方米）。公里）。一个更大的泥石流存款（105平方米。公里）在哥伦比亚的东科迪勒拉已知是史前的，但年龄和持续时间未知。因此，这两个设置表示近似的过程尺度端成员。哥伦比亚研究中心有一个碳-14定年存款，用于SGQ结果的一些年龄控制。如果这个项目是成功的，那么一个新的测年工具将可用于这样的景观沉积物，一个工具，覆盖范围从历史时期（过去几十年）回到ca。距今150万年，远远超出了碳14测年的范围泥石流是重大而棘手的事件。它们通常是由于另一个重大的地质或气候刺激因素，如冰川下的火山爆发或山区环境中的大雨而灾难性地发生的。泥石流是干旱区冲积扇形成的主要机制。在人类居住的地区，了解泥石流的持续时间和频率对于规划和应急反应至关重要。该项目将测试两个端元站点，以查看泥石流是否包含足够的单石英颗粒，这将允许确定可靠的年龄剖面。内华达州的场地有一个已知的年龄控制，哥伦比亚的场地有一些有机碳，可用于独立的测年评估。这种方法可能不合适，但如果它确实证明是成功的，它将为建立这些事件的年表提供一个新的途径。一个成功的测试项目将提供一个新的测年工具，以解决世界各地的史前碎屑流沉积物与各种可能的地质事件（如地震或火山爆发）在时间和空间上的关系。

Debris flows are mass-movement deposits, occurring worldwide, that shape landscapes and have caused considerable damage in historic times. Knowledge of their prehistoric frequency may be obtained by use of various dating methods (e.g., dendrochronology or Carbon-14), but these are not often possible given the age, complexity, and setting of the debris flow. This proposal will test the suitability of an alternate dating tool, single-grain-quartz (SGQ) luminescence dating. Single-grain and multigrain optical dating of quartz is a proven technology but has never been attempted with debris flows. Accurate optical dating depends upon resetting the clock by exposure to solar radiation over a minimum of tens of seconds. The turbulent and rapid process by which debris flows occur may not always allow entrained quartz grains sufficient time for such exposure. Two sites have been chosen for this test. A debris]flow site near Reno occurred in 1983 over a short duration (8 to 10 minutes) and small spatial extent (0.57 sq. km.). A much larger debris flow deposit (105 sq. km.) is known in the Eastern Cordillera of Colombia that is prehistoric, but of an unknown age and duration. Thus these two settings represent approximate process]scale end members. The Colombia site has a Carbon-14 datable deposit for some age control of the SGQ results. If this project is successful, then a new dating tool will be available for such landscape deposits, a tool covering the range from historic times (last few decades) back to ca. 150 ka, well beyond the Carbon-14 dating range. Debris flows are significant and troublesome events. They usually occur catastrophically in response to another significant geological or climatic stimulus, such as a sub-glacial volcanic eruption, or heavy rains in a mountainous environment. Debris flows are often the major mechanism in the construction of alluvial fans in arid regions. In areas of human habitation, knowledge of the duration and frequency of debris flows can be essential for planning and emergency response. This project will test two end-member sites to see if debris flows contain sufficient single quartz grains that will allow determination of a reliable age profile. The Nevada site has a known age control, and the Colombian site has some organic carbon that can be used for an independent dating assessment. It is possible that the method will not be suitable, but if it does prove successful, it will provide a new avenue for establishing the chronology of these events. A successful test project will provide a new dating tool to address the relationship in time and space of prehistoric debris-flow deposits worldwide to a wide variety of likely geologic events, such as earthquakes or volcanic eruptions.