The origin of Pangea

在过去的20年里，越来越多的证据表明，盘古大陆，一个形成于3亿年前的超级大陆，只是自前寒武纪早期以来不断形成的一系列超级大陆中最新的一个，这些超级大陆只是分裂和重新形成。尽管造成这种现象的机制存在争议，但许多地球科学家一致认为，超大陆合并和分散的反复循环对地壳、大气、气候和生命的演变产生了深远的影响。盘古大陆大约在2亿年前分裂，它的存在是板块构造的基石，在过去的5亿年里，盘古大陆的整合和分裂支配着地壳的演化。首先，我们知道盘古大陆形成的时间和地点，但不知道原因。在下一个拨款周期，我打算调查盘古大陆形成的原因。我的方法是将现场工作与实验室分析相结合，从揭示岩石单元之间关键关系的地点选择样本。研究生直接参与研究项目的每个阶段。我将继续研究莱西洋的演化，这是一个大约5亿年前在分散的大陆之间形成的海洋（一个内陆海洋），2亿年后它的关闭导致了盘古大陆的合并。然而，为了获得全球视野，我还需要研究记录古太平洋演变的岩石，古太平洋是包围分散大陆的“外部”海洋。如果这些海洋的演化是动态联系在一起的，那么大约4.4亿年前开始的内部海洋的收缩应该与外部海洋的扩张同时发生。实地工作的双重方法加上实验室分析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，并测试各种关于盘古大陆合并的假设（包括我自己的一些假设）。

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.