Orogen Hinterland Evolution: Testing Hypotheses using the Cretaceous to Eocene Stratigraphic Record in Eastern Nevada, USA

造山带腹地演化：利用美国内华达州东部白垩纪至始新世地层记录检验假设

• 批准号: 0610103
• 负责人: Andrew Hanson
• 金额: $ 16.41万
• 依托单位: University of Nevada Las Vegas
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-08-01 至 2009-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0610103&HistoricalAwards=false
• 关键词: Orogen; Hinterland; Evolution; Testing; Hypotheses

The deposition of the Sheep Pass Formation and correlative units of east-central Nevada records a critical geologic history of the Sevier hinterland during Late Cretaceous to Late Eocene time. This study provides a critical test to a variety of models pertaining to the kinematic role of the Sevier hinterland through time, how hinterland processes relate to the foreland, and how orogenic plateaus may evolve from the culmination of shortening to extensional collapse. In particular, questions pertaining to the timing and depositional setting of megabreccia deposits at the base of the Sheep Pass Formation relate directly to whether the Sevier hinterland experienced extension related to mid-crustal flow, or out-of-sequence shortening indicating that the upper crust was effectively decoupled from the mid-crust during the latest Cretaceous to Paleocene. Additionally, this study tests whether megabreccia deposition and the development of major angular unconformities overlying the Sheep Pass Formation indicate a major shift from shortening to extension within the Sevier hinterland during the Middle to Late Eocene. As part of this project, we are conducting detailed geologic mapping, stratigraphic measurements, and structural analyses to determine the tectonic setting of megabreccia deposits and syndepositional faults within the Sheep Pass Formation type section. Our new Argon-Argon dating provides the first absolute age control for the Sheep Pass Formation, brackets major angular unconformities and megabreccia at the top of the Sheep Pass Formation, and allows for regional correlations of tectonic events. Newly obtained fossil data also provides new opportunities for relative dating. We are currently compiling stratigraphic measurements, fossil data, geochronology, provenance and paleodispersal data from additional localities within the Sheep Pass Formation throughout east-central Nevada to reconstruct the Late Cretaceous to Eocene geologic history and paleogeography of the region. Additionally, our Uranium-Lead detrital zircon dating in collaboration with the University of Arizona provides opportunities to reconstruct the regional unroofing history, to identify the timing of initiation of Cenozoic volcanism, and the links between volcanism and tectonics within the Sevier hinterland. Similarly, our collaboration with Stanford University in measuring the oxygen isotope ratios of lacustrine carbonates within the Sheep Pass Formation will help determine how isotopic shifts relate to tectonic events. Although our focus is on what happened in one part of the Sevier orogenic system, our results have implications for ancient orogens in other regions, as well as modern orogenic systems. Our improved understanding of the tectonic and paleoelevation history of the hinterland plateau allows us to make a more comprehensive comparison to the well-determined evolution of the external fold-thrust belt. Research findings related to this project are being shared with the research community through presentations at national and regional conferences and through the eventual publication of maps and peer reviewed scientific journal articles. Results will both benefit and be of interest to workers within the fields of tectonics, structural geology, sedimentology, stratigraphy, geochronology, igneous petrology, paleontology and isotopic geochemistry. This project facilitates the professional development of Peter Druschke, a Ph.D. student, and two undergraduate students. Druschke in particular is receiving exceptional multidisciplinary training of great breath in basin analysis, and preparation for competitive research in an academic career, through study and interaction with a sedimentologist-stratigrapher, a structural geologist, stable isotope geochemist, two geochronologists, and a paleontologist. The undergraduate students additionally will work closely with the Druschke and the PI's and will benefit immensely from opportunities for investigative field research, exposure to a variety of advanced analytical techniques, and data analysis. In addition, students and collaborators involved with this project will benefit from cooperation and exchange between multiple academic institutions. This project is being supported with funds from the NSF Tectonics and EPSCoR programs.

绵羊通道组和内华达州中东部相关单位的沉积记录了晚白垩世至晚始新世期间塞维尔腹地的重要地质历史。这项研究提供了一个关键的测试，各种模型有关的运动学作用的塞维尔腹地通过时间，腹地过程如何与前陆，以及如何造山高原可能会演变的缩短到伸展崩溃的顶点。特别是，问题有关的时间和沉积环境的巨砾岩矿床的基础上的绵羊通过形成直接关系到是否塞维尔腹地经历了与中地壳流，或序列外缩短，表明上地壳有效地解耦中地壳在最后的白垩纪至古新世的延伸。此外，本研究测试是否megarccia沉积和发展的主要角度不整合覆盖绵羊通过形成表明一个重大转变，从缩短到扩展的塞维尔腹地在中始新世至晚始新世。作为该项目的一部分，我们正在进行详细的地质测绘、地层测量和结构分析，以确定绵羊通道地层类型段内巨砾岩沉积和同沉积断层的构造背景。我们新的氩-氩测年法首次提供了羊山口组的绝对年龄控制，在羊山口组顶部确定了主要的角度不整合面和巨砾岩，并允许构造事件的区域相关性。新获得的化石数据也为相对年代测定提供了新的机会。我们目前正在编译地层测量，化石数据，地质年代学，来源和paleodispersal数据从更多的地方内的绵羊通行证形成整个中东部内华达州重建晚白垩世到始新世地质历史和古地理的地区。此外，我们与亚利桑那大学合作的铀铅碎屑锆石测年提供了重建区域去顶历史的机会，以确定新生代火山活动的开始时间，以及塞维尔腹地火山活动和构造之间的联系。同样，我们与斯坦福大学合作测量羊嘴组内湖相碳酸盐的氧同位素比率，将有助于确定同位素变化与构造事件的关系。虽然我们的重点是在塞维尔造山系统的一部分发生了什么，我们的研究结果在其他地区的古代造山带，以及现代造山系统的影响。我们对内陆高原构造和古海拔历史的进一步了解使我们能够对外部褶皱冲断带的明确演化进行更全面的比较。 通过在国家和区域会议上的介绍以及最终出版地图和同行审查的科学期刊文章，与研究界分享与该项目有关的研究成果。研究结果将使构造学、构造地质学、沉积学、地层学、地质年代学、火成岩学、古生物学和同位素地球化学领域的工作者受益并感兴趣。该项目促进了Peter Druschke博士的专业发展。学生和两名本科生。 Druschke特别是正在接受特殊的多学科培训，在盆地分析方面具有很强的呼吸能力，并通过与沉积地层学家，结构地质学家，稳定同位素地球化学家，两名地质年代学家和一名古生物学家的学习和互动，为学术生涯中的竞争性研究做准备。 本科生还将与Druschke和PI密切合作，并将从调查性实地研究，接触各种先进的分析技术和数据分析的机会中受益匪浅。此外，参与该项目的学生和合作者将受益于多个学术机构之间的合作与交流。该项目得到了NSF Tectonics和EPSCoR计划的资金支持。