Deciphering paleogeography from orogenic architecture: Constructing orogens in a future supercontinent as thought experiment

IF 1.9 3区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY
Douwe J. J. van Hinsbergen,Thomas L. A. Schouten
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引用次数: 0

Abstract

Orogens that form at convergent plate boundaries typically consist of accreted rock units that form an incomplete archive of subducted oceanic and continental lithosphere, as well as of deformed lithosphere of the former upper plate. Reading the construction of orogenic architecture forms the key to decipher the pre-orogenic paleogeographic distribution of oceans and continents, as well as bathymetric and topographic features that existed thereon such as igneous plateaus, seamounts, microcontinents, or magmatic arcs. Current classification schemes of orogens divide between settings associated with termination of subduction [continent-continent collision, continent-ocean collision (obduction)] and with ongoing subduction (accretionary orogenesis), alongside intraplate orogens. Perceived diagnostic features for such classifications, particularly of collisional orogenesis, hinge on dynamic interpretations linking downgoing plate paleogeography to upper plate deformation, plate motion changes, or magmatism. Here, we show, however, that Mesozoic-Cenozoic orogens that undergo collision almost all defy these proposed diagnostic features and behave as accretionary orogens instead. To reconstruct paleogeography of subducted and upper plates, we therefore propose an alternative approach to navigating through orogenic architecture: subducted plate units comprise nappes (or mélanges) with Ocean Plate Stratigraphy (OPS) and Continental Plate Stratigraphy (CPS) stripped from their now-subducted or otherwise underthrust lower crustal and mantle lithospheric underpinnings. Upper plate deformation and paleogeography respond to the competition between absolute motions of the upper plate and the subducting slab. Our navigation approach through orogenic architecture aims to avoid a priori dynamic interpretations that link downgoing plate paleogeography to deformation or magmatic responses in the upper plate, to provide an independent basis for geodynamic analysis. From our analysis we identify ‘rules of orogenesis' that link the rules of rigid plate tectonics with the reality of plate deformation. We use these rules for a thought experiment, in which we predict orogenic architecture that will result from subducting the present-day Indian Ocean and colliding the Somali, Madagascar, and Indian margins using a published continental drift scenario for a future supercontinent as basis. We illustrate that our inferred rules (of thumb) generate orogenic architecture that is analogous to elements of modern orogens, unlocking the well-known modern geography as inspiration for developing testable hypotheses that aid interpreting paleogeography from orogens that formed since the birth of plate tectonics.
从造山带构造解读古地理:在未来的超大陆构造造山带作为思想实验
在会聚板块边界形成的造山带通常由增生的岩石单元组成,这些单元形成了俯冲的海洋和大陆岩石圈以及前上板块变形的岩石圈的不完整档案。阅读造山构造是破译海洋和大陆的前造山古地理分布,以及存在于其上的火成岩高原、海山、微大陆或岩浆弧等水深和地形特征的关键。目前造山带的分类方案分为与俯冲结束[大陆-大陆碰撞,大陆-海洋碰撞(逆冲)]和与持续俯冲(增生造山)有关的背景,以及与板内造山带有关的背景。这种分类的可感知诊断特征,特别是碰撞造山作用,取决于将下行板块古地理与上板块变形、板块运动变化或岩浆作用联系起来的动力学解释。然而,在这里,我们表明,经历碰撞的中新生代造山带几乎都违背了这些提出的诊断特征,而表现为增生造山带。因此,为了重建俯冲和上板块的古地理,我们提出了一种通过造山带构造导航的替代方法:俯冲板块单元包括推覆体(或称m langes)和海洋板块地层学(OPS)和大陆板块地层学(CPS),它们从现在俯冲或逆冲的下地壳和地幔岩石圈基础中剥离出来。上板块的变形和古地理是对上板块与俯冲板块绝对运动竞争的反应。我们通过造山带构造的导航方法旨在避免将下行板块古地理与上板块的变形或岩浆反应联系起来的先验动力学解释,为地球动力学分析提供独立的基础。从我们的分析中,我们确定了“造山规则”,它将刚性板块构造的规则与板块变形的现实联系起来。我们用这些规则做了一个思想实验,在这个实验中,我们预测造山带的构造将会由今天印度洋的俯冲和索马里、马达加斯加和印度边缘的碰撞而产生,并使用已发表的未来超大陆的大陆漂移情景作为基础。我们说明,我们推断的规则(经验)产生的造山带结构类似于现代造山带的元素,为开发可测试的假设提供灵感,这些假设有助于解释自板块构造诞生以来形成的造山带的古地理。
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来源期刊
American Journal of Science
American Journal of Science 地学-地球科学综合
CiteScore
5.80
自引率
3.40%
发文量
17
审稿时长
>12 weeks
期刊介绍: The American Journal of Science (AJS), founded in 1818 by Benjamin Silliman, is the oldest scientific journal in the United States that has been published continuously. The Journal is devoted to geology and related sciences and publishes articles from around the world presenting results of major research from all earth sciences. Readers are primarily earth scientists in academia and government institutions.
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