The origin of Pangea

过去20年里，越来越多的证据表明，3亿年前形成的超级大陆盘古大陆，只是自早前寒武纪以来反复形成的一系列超级大陆中的最新一块，只是为了再次解体和改革。尽管机制存在争议，但许多地球科学家一致认为，超大陆反复合并和扩散的循环已经对地壳、大气、气候和生命的演化产生了深远的影响。大约2亿年前解体的盘古大陆的存在是板块构造的基石，它的组装和碎裂在过去5亿年里主导了地壳的演化。首先，我们知道盘古大陆形成的地点和时间，但不知道为什么。在下一个赠款周期中，我打算调查盘古大陆形成的原因。我的方法是将野外工作与实验室分析相结合，对从暴露岩石单元之间关键关系的地点选择的样本进行分析。研究生直接参与研究项目的每个阶段。我将继续研究莱茵海的演化，这是一个大约5亿年前形成于分散大陆(内陆海洋)之间的海洋，2亿年后它的关闭导致了盘古大陆的合并。然而，为了获得一个全球视野，我还需要研究记录古太平洋演化的岩石，古太平洋是一个环绕着分散的大陆的“外部”海洋。如果这些海洋的演化是动态联系的，那么大约4.4亿年前开始的内海收缩应该与外部海洋的扩张同步。实地工作加上实验室分析的双重方法将使我能够测试内部和外部海洋之间潜在的地球动力学联系，并测试为合并盘古大陆而提出的各种假说(包括我自己的一些假说)。

Over the last 20 years, evidence has been amassing that Pangea, a supercontinent that formed 300 million years ago, is just the latest in a series of supercontinents that have formed repeatedly since the early Precambrian, only to break up and reform again. Although the mechanisms responsible are controversial, many geoscientists agree that repeated cycles of supercontinent amalgamation and dispersal have had a profound effect on the evolution of the Earth's crust, atmosphere, climate, and life. The existence of Pangea, which broke up about 200 million years ago, is a cornerstone of plate tectonics, and its assembly and fragmentation have governed the evolution of the Earth's crust for the past 500 million years. To a first order, we know where and when Pangea formed, but not why. Over the next grant cycle, I intend to investigate why Pangea formed. My approach is to combine field work with laboratory analyses of samples selected from sites that expose critical relationships between rock units. Graduate students are directly involved in each stage of the research program. I will continue to work on the evolution of the Rheic Ocean, an ocean that formed about 500 million years ago between dispersing continents (an interior ocean), and whose closure 200 million years later resulted in the amalgamation of Pangea. However, to obtain a global view, I also need to study rocks that document the evolution of the Paleopacific ocean, an "exterior" ocean that surrounded the dispersing continents. If the evolution of these oceans is dynamically linked, then contraction of the interior ocean, which began about 440 million years ago should be coeval with expansion of the exterior ocean. The dual approach of field work augmented by laboratory analysis will allow me to test the potential geodynamic connection between interior and exterior oceans and to test various hypotheses (including some of my own) that have been proposed for the amalgamation of Pangea.