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，将为理解全球气候温室时期的生物、水（水文学）和景观（环境）提供关键信息。纳瓦霍砂岩是迄今为止已知的最大的沙海（风成）系统，沉积于1.9亿至1.75亿年前（下侏罗纪）。结果将揭示生物群落结构如何响应气候变化从湿润到干燥的风成景观演替。这项研究将改变对最大风成系统的生物多样性、水文和环境因素的解释，以了解地球历史。该研究将成为评估风成系统气候敏感性的模型，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。研究将对解释古气候背景下生物、化学和物理沉积物记录之间的联系产生广泛的影响。我们的合作有一个坚定的承诺，即增加代表性不足群体的本科生和研究生参与研究和培训，并培训地球/空间科学教育专业的学生和教师。每位调查员都参与外展或地质教育工作。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、出版物或小册子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统纳瓦霍砂岩（Ss）古生态系统中记录的沉积学、水文学和生物学。纳瓦霍s代表了迄今为止已知的最大的能量系统，它沉积于：(1)泛大陆分裂后大季风气候系统的解体；(2)哺乳动物早期多样化；(3)增加了恐龙在大陆生态系统中的多样性和优势地位。将两个假设整合为一个广义模型，以理解在变干旱景观中陆地和水生生态系统对高频气候变化的响应，这些气候变化影响了古水文和古环境设置：（H1）纳瓦霍地区的气候和古水文状况从下部相对湿润到上部相对干燥，以及从东到西的区域性湿润到干燥。（H2）地下水由东向西由淡水向咸水演变，生物区系受其分布和水化学变化的强烈影响，以洞穴直径为基础的动物体型向上和区域向西减小。实地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，目的是进一步划分纳瓦霍族地层；(2)对凝灰岩进行C和O稳定同位素和岩石学分析，以提供古气候和水收支变化的数据；(3)结合沉积学、地层学、岩石学和地球化学对代表各种古环境的碎屑和碳酸盐相进行技术和古生物学分析。工作将集中在Moab西北地区，UT，这是最优先的目标区域，具有高度集中的洞穴带，植物化石，凝灰岩和湖泊沉积物，以解决H1和H2问题。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，我们可以进一步集中研究沿着这些时间线的可变性。

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.