Fluvial Systems and Climate in the Southwestern U.S.

美国西南部的河流系统与气候：河流系统通过侵蚀和沉积对气候变化做出反应，并创造了这些变化的地貌和地层记录。美国西南部的冲积扇保存了从数亿年到数百万年的这些变化的良好记录。经过几十年的野外和实验室工作，建立了一个大型的河流梯田和扇梯田数据库。这些梯田是西南景观的主要组成部分，控制着洪水灾害、土壤发育、生态系统甚至人类历史。然而，由于对河流系统反应的理解不足，我们阅读这些记录的能力有限。例如，是气候变化还是构造是西南地区冲积扇沉积事件的主要触发因素？河流系统的内部动力学是否可以解释我们观察到的许多阶地？沉积是发生在湿润期、干旱期还是两者之间的过渡时期？环境变化和河流系统反应之间的时间差是多少？为了回答这些问题，该项目将重点放在两个不同的时间尺度上。PI将在10 kyr到1 Myr的时间尺度上重建侵蚀和沉积的第四纪旋回。这种长期关注将使他能够确定同一盆地不同触发事件的震级和时间的影响。此外，PI将重建最新更新世和全新世侵蚀和沉积的时空变化，从100年到10年的时间尺度，在我们的研究区域，CA Cuyama山谷。这项工作将使具体的河流系统动力学和山坡响应机制进行评估。PI开发了一个基于过程的数值模型，用于研究复杂地形下的河道流动和泥沙运输，使他能够更好地了解河流系统如何响应气候变化。该模型使用现有的数字数据集以及气候和构造变化的情景来模拟特定研究区域的河流系统演化。拟议的研究将确定每个堑壕机制的阶地年龄和形态特征，以便确定形成西南冲积扇的主导过程。为此，将对河流系统对不同气候和构造历史的响应进行正演模拟，并将其结果与我们研究地区冲积扇阶地的年龄和几何形状进行比较。强大的定量方法背景对于为地球科学学生提供参与尖端科学所需的技能至关重要。作为该项目的第二阶段，我们将与地球科学教育专家合作，开发并整合一个互动版的数值模型到我们的课堂实验室中。

Fluvial Systems and Climate in the Southwestern U.S.(EAR-0309518Jon D. PelletierUniversity of ArizonaABSTRACTFluvial systems respond to changes in climate through erosion and deposition, creating a geomorphic and stratigraphic record of those changes. Alluvial fans of the southwestern U.S. preserve an excellent record of these changes from time scales of hundreds to millions of years. A large database of river and fan terraces has been developed from decades of field and laboratory work. These terraces are a major component of the Southwestern landscape, controlling flood hazards, soil development, ecosystems, and even human history. Our ability to read this record is limited, however, by a poor understanding of fluvial-system response. For example, is climate change or tectonics the major trigger of episodes of alluvial-fan deposition in the Southwest? Can the internal dynamics of the fluvial system be responsible for many of the terraces we observe? Does deposition occur during humid periods, arid periods, or the transitions between them? What are the time lags between environmental changes and fluvial-system response? To answer these questions, the project will focus on two distinct times scales. PI will reconstruct Quaternary cycles of erosion and deposition from time scales of 10 kyr to 1 Myr. This long-term focus will enable him to determine the effects of the magnitude and timing of different triggering events for the same basin. In addition, PI will reconstruct the spatial and temporal variability of latest Pleistocene and Holocene erosion and deposition from time scales of 100 yr to 10 kyr in our study area in Cuyama Valley, CA. This work will enable specific fluvial-system dynamics and hillslope-response mechanisms to be evaluated.PI has developed a process-based numerical model of channel flow and sediment transport in complex topography to enable him to better understand how fluvial systems respond to climatic changes. This model uses existing digital data sets together with scenarios of climatic and tectonic changes to model the fluvial-system evolution for specific study areas. The proposed research will determine the signatures of terrace age and morphology for each entrenchment mechanism so that the dominant processes that shape alluvial fans of the Southwest can be determined. To do this, forward modeling of fluvial-system response to different climatic and tectonic histories will be performed and their results compared against the ages and geometries of alluvial-fan terraces in our study areas.A strong background in quantitative methods is critical to providing geoscience students with the skills they need to take part in cutting-edge science. As a second phase of this project we will develop and integrate an interactive version of the numerical model into our classroom laboratory in collaboration with geoscience-education experts.