EAR-PF: Using distributions of channel geometry and channel belt properties to distinguish meandering and braided fluvial deposits in the rock record

美国国家科学基金会授予田东博士博士后奖学金，在得克萨斯大学奥斯汀分校进行研究和教育计划，由蒂莫西·古奇博士指导。该项目将研究在地球上观察到的两种主要河流形态之间的区别：单线和编织模式。在现代环境中，这些河流类型之间的区分是简单的，因为它们可以直接使用水文数据进行观察或预测。然而，在沉积岩记录中区分河道模式已被证明更为困难，因为只有残留的河道被保存下来，它们只占整个记录的一小部分。识别地质记录中的通道模式对于预测地下水和油气藏的质量和非均质性非常重要。通过该项目，将开发一套新的指标，用于利用河道和河道带的尺寸分布来区分河流类型（即，同一条河流在不同时期的河道沉积物收集），使用遥感数据从地球上的现代河流测量。这些指标，然后将解释在古代岩石记录中的河流类型之间的区别的背景下，与预期的结果有关的能源和水资源的安全在美国和相关行业。该项目还旨在通过GeoFORCE等推广计划和德克萨斯大学奥斯汀分校的研究机会，促进各级（K-12和本科生）STEM领域代表性不足的群体的参与。在现代环境中，使用河道坡度，宽度，深度和排水量的水力变量，可以相对较好地预测两种主要河流形态，单线和编织模式的形成。然而，在岩石记录中识别河道模式很困难，因为只保留了原始河道的残余。由于坡度和流量等水力变量无法在岩层中直接测量，因此这项工作将依赖于地质代理。除了区分河流类型以评估地下储层质量的重要性外，这种区分对于检验以下假设也很重要：在志留纪（~415至445 Ma）陆地植物到达之前，单线河流是否罕见。以前的研究已经重建了上述四个水力变量，以区分岩石记录中的通道模式，但这样的结果有不确定性，范围高达一个数量级，由于复合计算误差。这项研究提出了开发新的诊断指标，使用分布的水力变量和河道带属性（例如，宽度和曲率半径），通过遥感技术从世界各地的现代河流系统测量，最终目的是区分岩石记录中的河道类型。具体来说，我们的目标是测试的假设，编织和单线河流有不同的分布的通道几何形状和通道带属性的理论支持的河流分支。我们预计，这项研究的结果将是广泛适用的，几何变量，如宽度和深度，和通道带宽度很容易测量，或可以重建与最小的计算步骤跨越观测的长度尺度，从露头到地震图像，时间尺度，从现代系统到古代沉积矿床，并跨地区，从地球到其他行星。该项目得到了地球科学部地貌学和土地利用动力学项目的共同资助。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

An NSF EAR Postdoctoral Fellowship has been granted to Dr. Tian Dong to carry out research and education plans at the University of Texas at Austin under the mentorship of Dr. Timothy Goudge. This project will study the distinctions between the two dominant river morphologies observed on Earth: single-thread and braided patterns. Distinguishing between these river types is straightforward in the modern environment as they can be directly observed or predicted using hydrological data. However, distinguishing channel patterns in the sedimentary rock record has proven more difficult, as only remnants of the river channels are preserved and they only account for a small fraction of the overall record. Identifying channel patterns in geologic records is important for predicting the quality and heterogeneity of groundwater and hydrocarbon reservoirs. Through this project, a new set of metrics will be developed for distinguishing river types using distributions of the dimensions of river channels and channel belts (i.e., collections of channel deposits from the same river at different times), measured from modern rivers on Earth using remote sensing data. These metrics will then be interpreted in the context of distinguishing between river types in the ancient rock record, with the anticipated findings relevant for the security of energy and water resources in the United States and related industries. This project also aims to promote participation of underrepresented groups in STEM fields at all levels (K-12 and undergraduate) through outreach programs such as GeoFORCE and research opportunities at the University of Texas at Austin.Formation of the two main river morphologies, single-thread and braided patterns can be relatively well predicted in modern environments using hydraulic variables of channel slope, width, depth, and water discharge. However, recognition of channel patterns in the rock record is difficult because only remnants of the original river channels are preserved. Since hydraulic variables such as slope and discharge cannot be measured directly in rock formations, this work will rely on geologic proxies. In addition to the significance of distinguishing river types to assess subsurface reservoir quality, this distinction is important for testing the hypothesis that whether single-thread rivers were rare prior to the arrival of land plants in the Silurian (~415 to 445 Ma). Previous studies have reconstructed the above four hydraulic variables to distinguish channel patterns in the rock record, but such results have uncertainties that range up to an order of magnitude due to compounded calculation errors. This study proposes to develop new diagnostic metrics using distributions of hydraulic variables and channel belt properties (e.g., width and radius of curvature), measured from modern fluvial systems worldwide via remote sensing techniques, with the ultimate aim for distinguishing channel types in the rock record. Specifically, we aim to test the hypothesis that braided and single-thread rivers have distinct distributions of channel geometry and channel belt properties as supported by theories on river branching. We anticipate that the results of this study will be widely applicable, as geometry variables, such as width and depth, and channel belt width are easily measurable or can be reconstructed with minimum calculation steps across observational length scales, from outcrops to seismic images, timescales, from modern systems to ancient sedimentary deposits, and across localities, from Earth to other planets. This project received co-funding from the Geomorphology and Land-use Dynamics program in the Earth Science division.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.