Collaborative Research: Unlocking secrets of Earth's largest sand sea: Paleoenvironmental records of the Lower Jurassic Navajo Sandstone, Colorado Plateau, USA.

对保存在纳瓦霍砂岩中的古代（古）生态系统的研究，是已知的最大的沙海（风成）系统，沉积于1.9亿至1.75亿年前（下侏罗纪），将为了解全球气候温室期的生物，水（水文）和景观（环境）提供重要信息。研究结果将揭示生物群落结构如何响应气候变化的过渡过程中，从潮湿到干燥的风成景观演替。这项研究将改变如何解释最大的风成系统的生物多样性，水文和环境因素，以了解地球历史。该研究将为评估风成系统的气候敏感性提供一个模型，并为未来全球变暖循环中的水文、生态和气候研究提供指导。研究将产生广泛的影响，以解释生物，化学和物理沉积物记录在古气候背景下之间的联系。我们的合作有一个坚定的承诺，以增加本科生和研究生的研究和培训，并培训地球/空间科学教育专业和教师的代表性不足的群体的参与。每个调查员都参与外联或地质教育工作。由于纳瓦霍砂岩在科罗拉多高原的许多国家公园、纪念碑、公共土地和荒野地区的突出地位，研究结果将对公众具有很高的知名度。与政府机构的伙伴关系将确保通过视频模块、图片和网站、出版物或手册的科学内容向公众和中学地球科学教师广泛传播科学成果。这项跨学科研究将研究美国科罗拉多高原下侏罗纪纳瓦霍砂岩（Ss）古生态系统中记录的沉积学、水文学和生物学。纳瓦霍Ss代表了有史以来最大的erg系统，沉积于：（1）泛大陆解体后的大季风气候系统解体;（2）哺乳动物的早期多样化;（3）恐龙在大陆生态系统中的多样性和优势增加。两个假设，以了解陆地和水生生态系统的响应高频气候变化，影响古水文和古环境设置在干旱景观将被整合到一个通用的模型：（H1）的气候和古水文状态的纳瓦霍Ss演变从相对潮湿的下部相对干燥的上部，以及区域潮湿干燥从东到西。(H2)地下水从东向西从淡水演变为咸水，生物群受到其分布和水化学变化的强烈影响，根据洞穴直径，动物体型在向上部分和区域向西减小。野外和实验室研究将包括：（1）在地层框架内进行地层学和沉积学分析，以系统地记录垂直变化，目的是细分纳瓦霍Ss;（2）对凝灰岩进行C和O稳定同位素和岩相学分析，以提供有关古气候和水收支变化的数据;（3）遗迹学和古生物学分析与代表各种古环境的碎屑岩和碳酸盐岩相的沉积学、地层学、岩相学和地球化学分析相结合。工作将集中在犹他州摩押西北部地区，这是最优先的目标区域，具有高度集中的洞穴区，植物化石，石灰华和湖泊沉积物，以解决H1和H2。露头暴露非常好，这将有助于建立可靠的时间表。当我们建立这些时间线时，我们可能会进一步关注研究，以关注沿着这些时间线的变异性。

Study of ancient (paleo-) ecosystems preserved in the Navajo Sandstone, the largest sand sea (eolian) system ever known that was deposited between 190 and 175 million years ago (Lower Jurassic), will provide crucial information to understanding biotic, water (hydrology), and landscape (environments) during a greenhouse period of global climate. Results will reveal how biotic community structure responded to climate changes during the transition from wetter to drier eolian landscape successions. This study will transform how biodiversity, hydrology, and environmental factors of the largest eolian systems are interpreted for understanding Earth history. This study will be a model for evaluating climate sensitivities in eolian systems, and provide guidance on future hydrologic, ecologic, and climatic studies in global warming cycles. Research will have broad impacts to interpret the links between biological, chemical, and physical sediment records in a paleoclimate context. Our collaboration has a firm commitment to increase involvement of undergraduate and graduate students of underrepresented groups in research and training, and training of Earth/Space Science education majors and teachers. Each Investigator is involved with outreach or geologic education efforts. Study results will have high visibility to the public because of the prominence of the Navajo Sandstone in so many of the Colorado Plateau's National Parks, Monuments, public lands, and wilderness areas. Partnerships with government agencies will ensure broad dissemination of scientific results to the general public and secondary geoscience teachers via video modules, pictures, and science content for websites, publications or brochures.This interdisciplinary study will examine the sedimentology, hydrology, and biology recorded within paleoecosystems of the Lower Jurassic Navajo Sandstone (Ss) on the Colorado Plateau, USA. The Navajo Ss represents the largest erg system ever known, deposited during the: (1) disintegration of the megamonsoonal climate system after the breakup of Pangea; (2) early diversification of mammals; and (3) increased diversity and dominance of dinosaurs in continental ecosystems. Two hypotheses to understand the response of terrestrial and aquatic ecosystems to high-frequency climatic changes that affected paleohydrologic and paleoenvironmental settings in a variably arid landscape will be integrated into one generalized model: (H1) The climatic and paleohydrologic status of the Navajo Ss evolved from relatively moist in the lower part to relatively dry in the upper part, as well as regionally moist to dry from east to west. (H2) Groundwater evolved from fresh to saline from east to west across the basin, and biota was strongly influenced by its distribution and the change in water chemistry, such that animal body size, based on burrow diameters, decreases up-section and regionally towards the west. Field and laboratory studies will include: (1) stratigraphic and sedimentologic analyses in a stratigraphic framework to systematically document vertical changes, with the objective to subdivide the Navajo Ss: (2) C and O stable isotopic and petrographic analyses of tufas to provide data on paleoclimate and changes in the water budget; and (3) ichnological and paleontological analyses integrated with sedimentologic, stratigraphic, petrographic, and geochemical analyses of clastic and carbonate facies that represent a variety of paleoenvironments. Efforts will focus in the area northwest of Moab, UT, which is the highest priority target area with a high concentration of burrowed zones, plant fossils, and tufa and lacustrine deposits to address H1 and H2. Outcrop exposure is exceptionally good, which will facilitate establishing reliable timelines. As we establish these timelines, we may focus the study further to concentrate on the variability along those timelines.