RUI: Magnetostratigraphy of the Eocene-Oligocene Transition in Tran-Pecos Texas

始新世-渐新世的过渡(约4200万至3000万年前)是自恐龙灭绝以来气候变化和大规模灭绝最重要的时期。在这一过渡期间的物种灭绝归因于许多原因，包括陨石或彗星撞击、火山活动以及南极冰川和海洋变化导致的气候降温。最近的研究表明，最戏剧性的变化发生在始新世中后期。德克萨斯州的外佩科斯地区是北美唯一一个由叠加的哺乳动物动物群记录到这种变化的地方，通过辐射计量学和磁性地层学都可以得出数据。在北美没有一个地方包含这个时代的指间海洋/非海洋序列，所以这个区域是解开陆地哺乳动物Uintan-Duchenean-Chadronian过渡细节的关键。内贝科斯岩中含有大量研究较好的始新世中期(Uintan)和晚始新世(Duchernean和Chadronian)时代的动物群。尽管已经对这些岩石进行了初步的古地磁研究，但许多关键的化石地点，以及该部分的大部分乌伊坦和查德罗尼亚部分，从未被取样。该项目将收集和分析大部分关键地区的古地磁样品，并提供新的40Ar/39Ar年龄，以改进地质年代学。然后，就有可能将整个北美西部的乌伊坦、杜切斯和查德罗尼亚动物群与磁极时间尺度联系起来。然后，可以更详细地研究物种灭绝和动物群变化的事件，并将其与始新世-渐新世过渡期间气候和生物变化的全球记录更精确地关联起来。

The Eocene-Oligocene transition (about 42 to 30 million years ago) was the most significant episode of climatic change and mass extinction since the demise of the dinosaurs. The extinctions during this transition have been attributed to many causes, including meteorite or cometary impacts, volcanism, and climatic cooling due to Antarctic glaciation and oceanographic changes. Recent research has shown that the most dramatic changes occur between the middle and late Eocene. The Trans-Pecos region of Texas is the only place in North America where this change is recorded by superposed mammalian faunas datable by both radiometrics and magnetostratigraphy. There is no place in North American the contains interfingering marine/non-marine sequence of this age, so this area is the key to unlocking the details of the Uintan-Duchesnean-Chadronian transition in land mammals. The Trans-Pecos rocks contain a number of well studied faunas of middle Eocene (Uintan) and late Eocene (Duchesnean and Chadronian) age. Although preliminary paleomagnetic studies have been on some these rocks, many of the key fossil localities, and most of the Uintan and Chadronian parts of the section, have never been sampled. This project will collect and analyzed paleomagnetic samples from most of the key localities, and provide new 40Ar/39Ar dates to improve the geochronology. It will then be possible to correlate Uintan, Duchesnean, and Chadronian faunas from all over western North America to the magnetic polarity timescale. Episodes of extinction and faunal change can then be examined in greater detail, and correlated more precisely with the global record of climatic and biotic change during the Eocene-Oligocene transition.