High-precision U-Pb zircon geochronology and intracontinental correlation of terrestrial ecosystems during the "zenith" of dinosaur diversity in the Late Campanian of North America

北美晚寒武世恐龙多样性“顶峰”时期陆地生态系统的高精度U-Pb锆石年代学和陆内对比Samuel BowringEAR-1424892--MITABSTRACTNON-技术概述：一个主要问题是全球环境变化是否导致生物进化的变化。8000万年前到7000万年前之间的时间段被描述为？顶峰？北美洲西部拥有无与伦比的岩石裸露，拥有这一时期丰富的恐龙化石。我们没有很好地理解是什么触发了这种进化多样性的爆发，但我们确实知道，同时也发生了深刻的全球范围的环境变化，包括全球大气温度的上升和海平面的突然上升。然而，一些人认为，生物多样性的明显增加更多地与保护而不是进化有关。为了测试全球环境变化或优先保护的责任，我们必须能够将加拿大南部到美国西南部的岩石和化石联系起来。该项目将专注于火山岩与化石岩石夹层的高精度测年，以便我们确定北美西部超过2000公里纬度的演化速度。这将使我们能够反过来评估保存在岩石中的环境变化证据是否与恐龙进化相关。技术摘要该项目将致力于在北美西部内陆盆地(拉米迪亚)保存的一条2000公里长的晚寒武世(白垩纪)地层走廊上，开发一种约1000万年(80-70 Ma)的无与伦比的年代地层学。这是世界上面积最广、化石最多的大陆序列之一，其中包括著名的两个梅迪奇--蒙大拿州和怀俄明州的朱迪斯河动物群/植物群、艾伯塔省的恐龙公园动物群/植物群、犹他州的凯帕罗威斯动物群/植物群、新墨西哥州的柯特兰-水果地动物群/植物群和得克萨斯州的阿古贾动物群。研究小组将使用火山灰岩层上的高精度U-Pb锆石年代学来建立每个地区的年龄模型，并允许详细的对比和对进化/保存趋势的洞察。西部内陆盆地在许多与晚白垩世脊椎动物有关的假说的形成和评估中发挥了关键作用，从生理和行为到生物地理和进化。在西部内陆南部(即犹他州、新墨西哥州、德克萨斯州、墨西哥)和遥远的北部(阿拉斯加)最近的发现揭示了新的坎帕尼亚时代的脊椎动物群，其中突出的是一系列以前不为人知的恐龙、其他脊椎动物和植物。经过一个多世纪的密集采样和研究，人们对来自拉拉米迪亚(北美西部)的坎帕尼亚陆生脊椎动物的了解比任何其他中生代大陆规模的地区都要多。因此，驼背脊椎动物可以说是研究围绕中生代陆生脊椎动物进化的节奏和模式以及相关的生态系统变化的主要问题的最佳时间和地点。在古代生态系统中解决这类问题的一个主要障碍是能否准确和准确地限制重要化石地点的沉积年龄，并在空间上将植物群和动物群联系起来。利用锆石U-Pb年代学方法，可以确定火山灰岩层的年龄为9000万年左右，早于±2万-3万年。当在地层序列中确定多个火山灰层的年代时，可以建立年龄模型，以便能够在千年到十年级别进行高精度的对比。拟议的项目将专注于以下关键的动物群和植物群：1)蒙大拿州和怀俄明州的两个梅迪奇-朱迪斯河组；2)艾伯塔省的恐龙公园组；3)犹他州的凯帕罗维斯组；4)新墨西哥州的富里特兰-柯特兰组；以及德克萨斯州的阿古贾组。这些大陆单位及其植物群和动物群被解释为同时代的，通过开发高精度的年代地层学，研究小组将创造一个无与伦比的机会，研究中生代陆地生态系统的演化模式和速度，并有机会调查和测试纬向排列的地区性、周转率、进化变化中的历时性、分子研究的预测以及欢喜、构造和气候作为此类变化驱动因素的作用。此外，一旦完成，将有可能将拉拉米迪亚的记录与南美洲和亚洲的记录进行比较。

High-precision U-Pb zircon geochronology and intracontinental correlation of terrestrial ecosystems during the 'zenith' of dinosaur diversity in the Late Campanian of North AmericaSamuel BowringEAR-1424892--MITABSTRACTNon-technical overview:A major question is whether global environmental change cause changes in biological evolution. The time period between 80 and 70 million years ago has been described as the ?zenith? of dinosaur diversity and western North America contains unparalleled exposures of rocks with abundant dinosaur fossils from this time period. We do not have a good understanding of what triggered this burst of evolutionary diversity but we do know that at the same time were profound, global-scale environmental changes, including an increase in global atmospheric temperatures and an abrupt rise in sea level. However some have argued that the apparent increase in diversity has more to do with preservation than evolution. To test whether global environmental changes or preferential preservation are responsible, we must be able to correlate rocks and fossils from southern Canada to the southwestern United States. This project will focus on high precision dating of volcanic rocks interlayered with fossil bearing rocks so that we determine the rates of evolution across more than 2000 km of latitude in western North America. This will allow us to in turn evaluate whether evidence for environmental change preserved in the rocks can be correlated with dinosaur evolution. Technical AbstractThis project will focus on developing an unparalleled chronostratigraphy for an approximately ten million year (80-70 Ma) interval across a 2000 km long corridor of Late Campanian (Cretaceous) strata preserved in the Western Interior Basin of western North America (Laramidia). This represents one of the most laterally extensive and fossiliferous continental successions in the world, and includes the famous Two Medicine-Judith River fauna/flora in Montana and Wyoming, the Dinosaur Park fauna/flora in Alberta, the Kaiparowits fauna/flora in Utah, the Kirtland-Fruitland fauna/flora in New Mexico and the Aguja fauna in Texas. The research team will use high-precision U-Pb zircon geochronology on volcanic ash beds to build age models for each area and allow detailed correlations and insight into evolutionary/preservation trends.The Western Interior Basin has been pivotal in the formation and assessment of many hypotheses relating to Late Cretaceous vertebrates, from physiology and behavior to biogeography and evolution. Recent discoveries from the southern Western Interior (i.e., Utah, New Mexico, Texas, Mexico) and the far north (Alaska) have revealed new Campanian-aged vertebrate faunas, highlighted by an array of previously unknown dinosaurs, other vertebrates and plants. Following more than a century of intense sampling and study, more is known about Campanian terrestrial vertebrates from Laramidia (western North America) than from any other continent-scale region of Mesozoic age. Thus, Campanian Laramidia represents arguably the best time and place to investigate major questions surrounding the tempo and mode of evolution among Mesozoic terrestrial vertebrates and associated ecosystem changes. A major hurdle to addressing questions of these types in ancient ecosystems is the ability to precisely and accurately constrain the depositional age of important fossil localities and to correlate floras and faunas through space. U-Pb zircon geochronology can be used to date ca 90 million year old volcanic ash beds to better than ± 20-30 thousand years. When multiple ash beds are dated in stratigraphic succession, age models can be constructed that allow resolution at millennial to decamillenial levels and thus high-precision correlation.The proposed project will focus on the following key faunas and floras: 1) the Two Medicine-Judith River formations in Montana and Wyoming; 2) the Dinosaur Park Formation in Alberta; 3) the Kaiparowits Formation in Utah; 4) the Fruitland-Kirtland formations in New Mexico; and the Aguja Formation in Texas. Together, these continental units and their floras and faunas have been interpreted as contemporaneous, and by developing a high precision chronostratigraphy, the research team will create an unparalleled opportunity for investigating the mode and tempo of evolution in a Mesozoic terrestrial ecosystem, with opportunities for investigating and testing concepts of latitudinally arrayed provinciality, turnover rates, diachroneity in evolutionary changes, predictions from molecular studies and the roles of eustasy, tectonics and climate as drivers of such changes. In addition, once completed, it will be possible to compare the record from Laramidia with those from South America and Asia.