A Quantitative Tomotectonic Plate Reconstruction of Western North America and the Eastern Pacific Basin
A Quantitative Tomotectonic Plate Reconstruction of Western North America and the Eastern Pacific Basin
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DOI：
10.1029/2020gc009117
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发表时间：
2020-08-01
影响因子：
3.5
通讯作者：
Mueller, R. Dietmar
中科院分区：
文献类型：
--
作者：
Clennett, Edward J.;Sigloch, Karin;Mueller, R. Dietmar
自盘古大陆分裂以来的板块重建大多基于保存下来的海洋盆地扩张历史，在绝对参考系内受到年龄渐进热点轨迹和古地磁数据的约束。由于许多证据已被消减，破坏性板块边缘的演化很难从表面观测中得到限制。地震层析成像可以通过对地幔中俯冲的岩石圈进行成像来直接限制古海沟的位置。这一新证据与俯冲的地质表面记录相结合，表明中生代晚期法拉隆洋和北美之间存在多个洋内弧，这与通常显示法拉隆板块在大陆边缘下方长期俯冲的现有定量模型形成鲜明对比。我们提出了东太平洋盆地从 170 Ma 到现在的连续闭合板块模型，并使用“层析构造分析”（地表和地下数据的整合）进行约束。在中侏罗世到晚侏罗世期间，我们显示了海洋板块同时向东和向西俯冲到由科迪勒拉弧地体组成的群岛之下。随着北美向西漂移，从侏罗纪末期开始，它历时地覆盖了群岛及其弧线。在吸积过程中和吸积后，受古地磁证据的限制，科迪勒拉地体沿着大陆边缘平移了数千公里。北美洲的最终吸积发生在始新世期间，其结局类似于群岛覆盖 100 密尔。该模型提供了东太平洋地区详细、定量的构造历史，为层析构造分析在其他古海洋区域的应用铺平了道路。 简单语言摘要 侏罗纪时期的构造板块重建主要基于保存下来的洋壳数据。然而，许多海洋板块因俯冲作用已经消失到地球内部，这使得它们的重建成为一个挑战。我们将地幔深处的地震图像与地质数据结合起来，找到地幔中消失的板块，并将它们恢复到之前在地表的位置。板块俯冲的海沟可以与北美西部的死弧火山配对。这些证据共同表明，东太平洋盆地被分解成几个较小的板块，这与长期以来认为一两个大板块在过去 170 迈尔向东俯冲到北美西海岸下方的观点形成鲜明对比。相反，我们模拟了原太平洋东北部静止不动的巨大火山弧群岛下板块同时向东和向西俯冲的情况。北美被向西拉入这个群岛，并逐渐与其微大陆相碰撞，形成了今天的北美科迪勒拉山脉。我们的模型提供了东太平洋更详细、更完整的构造历史，并强调了如何使用我们的方法重建消失的海洋。
Plate reconstructions since the breakup of Pangaea are mostly based on the preserved spreading history of ocean basins, within absolute reference frames that are constrained by a combination of age-progressive hotspot tracks and paleomagnetic data. The evolution of destructive plate margins is difficult to constrain from surface observations as much of the evidence has been subducted. Seismic tomography can directly constrain paleotrench locations by imaging subducted lithosphere in the mantle. This new evidence, combined with the geological surface record of subduction, suggests that several intraoceanic arcs existed between the Farallon Ocean and North America during late Mesozoic times-in contrast to existing quantitative models that typically show long-lived subduction of the Farallon plate beneath the continental margin. We present a continuously closing plate model for the eastern Pacific basin from 170 Ma to present, constrained using "tomotectonic analysis"-the integration of surface and subsurface data. During the Middle to Late Jurassic, we show simultaneous eastward and westward subduction of oceanic plates under an archipelago composed of Cordilleran arc terranes. As North America drifts westward, it diachronously overrides the archipelago and its arcs, beginning in the latest Jurassic. During and post-accretion, Cordilleran terranes are translated thousands of kilometers along the continental margin, as constrained by paleomagnetic evidence. Final accretions to North America occur during the Eocene, ending similar to 100 Myr of archipelago override. This model provides a detailed, quantitative tectonic history for the eastern Pacific domain, paving the way for tomotectonic analysis to be used in other paleo-oceanic regions.Plain Language Summary Tectonic plate reconstructions back to the Jurassic period are mostly based on data from preserved ocean crust. However, many oceanic plates have been lost into the Earth's interior by subduction, making their reconstruction a challenge. We combine seismic images of the deep mantle with geological data to locate the vanished plates in the Earth's mantle and restore them to their previous positions at the surface. The trenches where the plates subducted can be paired with extinct arc volcanoes in western North America. Jointly, these lines of evidence suggest that the eastern Pacific basin was broken up into several smaller plates-in contrast to the long-held view that one or two large plates subducted eastward beneath the west coast of North America for the last 170 Myr. Instead, we model simultaneous eastward and westward subduction of plates under a vast archipelago of volcanic arcs that sat stationary in the northeastern proto-Pacific. North America was pulled westward into this archipelago and gradually collided with its microcontinents, which today form the North American Cordillera. Our model provides a more detailed and complete tectonic history for the eastern Pacific and highlights how our method can be used to reconstruct vanished oceans.