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

对纳瓦霍砂岩中保存的古代(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)和景观(环境)提供关键信息。纳瓦霍砂岩是迄今已知的最大的沙海(风成)系统，沉积于1.9亿至1.75亿年前(下侏罗纪)。研究结果将揭示生物群落结构在从湿润到干燥的风沙景观演替过程中对气候变化的响应。这项研究将改变对最大的风沙系统的生物多样性、水文学和环境因素的解释，以了解地球历史。这项研究将成为评估风沙系统气候敏感性的模式，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影响。我们的合作坚定地致力于让代表性不足群体的本科生和研究生更多地参与地球/空间科学教育专业和教师的研究和培训。每个调查员都参与了外展或地质学教育工作。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都很突出，因此研究结果将对公众具有很高的可见度。与政府机构的合作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普通公众和中学地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SS是迄今已知的最大的ERG系统，沉积于：(1)泛古大陆解体后的大季风气候系统；(2)哺乳动物的早期多样化；(3)大陆生态系统中恐龙的多样性和优势地位的增加。为了理解陆地和水生生态系统对高频气候变化的响应，这两个假设将被整合到一个通用模型中：(H1)纳瓦霍SS的气候和古水文状况从下部相对潮湿演变到上部相对干燥，以及从东到西从区域潮湿到干燥。(H2)整个盆地的地下水从东到西由淡水演化到咸水，生物群受到其分布和水化学变化的强烈影响，因此，根据洞穴直径，动物身体的大小在向上和向西区域减小。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，目的是对纳瓦霍盆地进行细分；(2)对凝灰岩进行碳和氧稳定同位素和岩石学分析，以提供有关古气候和水收支变化的数据；(3)结合沉积学、地层学、岩石学和地球化学分析，对代表多种古环境的碎屑和碳酸盐相进行综合分析。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，洞穴地带、植物化石以及凝灰岩和湖泊沉积物高度集中，以解决H1和H2问题。露头露头非常好，这将有助于建立可靠的时间表。随着我们建立这些时间线，我们可以进一步将研究重点放在这些时间线上的可变性上。

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.