Collaborative Research: Quantitative Reconstruction of Paleohydraulics of the Kayenta Formation - Implications for Paleoclimate Reconstruction

古河流系统古斜坡的确定在定量限制大陆序列的构造和古气候历史方面具有潜在的广泛应用，但在很大程度上尚未开发。这个项目的目标是，首先，充实计算古斜坡和相关信息的新方法，如砂质辫状河沉积物的水和沉积物通量。第二个目标是将该方法应用于科罗拉多高原的Kayenta组（侏罗纪），以证明该方法在从区域尺度上发现的河流沉积物的古代记录中重建长期气候变化方面的实用性。本文提出的重建古气候的关键是通过估算古流深（由坝形确定）和古坡度计算来估算古水通量。古尺度计算采用了一种利用劳斯数的新方法，劳斯数是水流中河床荷载和悬浮荷载之间粒度分异的指标。应用该方法的关键工具是使用麻省理工学院的设备进行高精度、快速的粒度测定。初步结果表明，该方法在现代也适用，并与kayentinformation进行了非常一致的比较。气候对河流系统影响的理论模型表明，长期气候变化可能产生与短期（米兰科维奇尺度）变化非常不同的地层记录。因此，将该方法应用于古代不仅提供了该方法可以做什么的一个例子，而且将有助于回答一些具体的问题，如格伦峡谷群的温盖特-卡耶塔-纳瓦霍地层所代表的从干燥到潮湿再到干燥的长期变化是如何影响系统的。通过系统地将该方法应用于Kayenta地层，我们将获得古流量（斜坡和水通量）方面的统计显著概率分布，可以在单元内的不同地点之间进行比较，以显示河流系统如何随盆地和时间而变化。这样的应用将证明古水力重建方法在古气候重建中的实用性，这种方法可以应用于古代记录中的其他砂质河流沉积。该研究的更广泛的方面包括培训怀俄明大学的一名女博士生，学习沉积定量方法。作为该项目的一部分，麻省理工学院的本科生也将接受实地和实验室技术方面的培训。此外，该研究还包括与NCED（国家地球表面动力学中心）设施的联系，允许该nsf资助的科学技术中心的扩展。

Determination of paleoslopes in ancient fluvial systems has potentially broad, butlargely untapped, application to quantitatively constraining the history of tectonics andpaleoclimate in continental sequences. The objective of this project is to, first, flesh out anew approach to calculating paleoslope and associated information, such as water andsediment flux, from sandy braided stream deposits. The second objective is to apply themethod to the Kayenta Formation (Jurassic) on the Colorado Plateau to demonstrate theutility of the method in reconstructing aspects of long-term climate change from theancient record of fluvial deposits found on a regional scale. The key to reconstructingpaleoclimate as proposed here is to estimate paleowater flux from estimates of paleoflowdepth (as determined from bar forms) and calculations of paleoslope. Paleoslopecalculation follows a novel approach utilizing the Rouse Number, an indicator of grainsizefractionation between bed load and suspended load in water flows. The key tool toapplying the method is the use of high-precision, rapid, grain-size determinationsavailable using equipment housed at M.I.T. Preliminary results show the approach workswell in the modern and yields remarkably consistent comparisons with the KayentaFormation. Theoretical modeling of climate impact on fluvial systems suggests that longtermclimate change may produce a very different stratigraphic record than short-term(Milankovich scale) changes. Hence application of the method to the ancient not onlyprovides an example of what the method can do, but will help answer specific questionsregarding how the long-term change from dry to wet to dry conditions represented by theWingate-Kayenta-Navajo formations of the Glen Canyon Group, respectively, affectriver systems. By systematically applying the methodology to the Kayenta Formation, wewill obtain statistically significant probability distributions of aspects of paleoflow (slopeand water flux) that can be compared between sites within the unit to show how riversystems changed down basin and over time. Such an application will demonstrate theutility of the paleohydraulic reconstruction approach to paleoclimate reconstruction thatcan be applied to other sandy fluvial deposits in the ancient record.The broader aspects of the study include training a female Ph.D. student at theUniversity of Wyoming in quantitative methodologies of sedimentation. Anundergraduate at M.I.T. will also be trained in field and laboratory techniques as part ofthis project. In addition, the research includes a tie to an NCED (National Center forEarth-Surface Dynamics) facility, allowing for outreach of this NSF-funded Science andTechnology Center.