Tectonic Reorganization of the Caribbean Plate System in the Paleogene Driven by Farallon Slab Anchoring

IF 2.9 2区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Ethan M. Conrad, Claudio Faccenna, Adam F. Holt, Thorsten W. Becker
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Abstract

The tectonic configuration of the Caribbean plate is defined by inward-dipping double subduction at its boundaries with the North American and Cocos plates. This geometry resulted from a Paleogene plate reorganization, which involved the abandonment of an older subduction system, the Great Arc of the Caribbean (GAC), and conversion into a transform margin during Lesser Antilles (LA) arc formation. Previous models suggest that a collision between the GAC and the Bahamas platform along the North American passive margin caused this event. However, geological and geophysical constraints from the Greater Antilles do not show a large-scale compressional episode that should correspond to such a collision. We propose an alternative model for the evolution of the region where lower mantle penetration of the Farallon slab promotes the onset of subduction at the LA. We integrate tectonic constraints with seismic tomography to analyze the timing and dynamics of the reorganization, showing that the onset of LA subduction corresponds to the timing of Farallon/Cocos slab penetration. With numerical subduction models, we explore whether slab penetration constitutes a dynamically feasible set of mechanisms to initiate subduction in the overriding plate. In our models, when the first slab (Farallon/Cocos) enters the lower mantle, compressive stresses increase at the eastern margin of the upper plate, and a second subduction zone (LA) is initiated. The resulting first-order slab geometries, timings, and kinematics compare well with plate reconstructions. More generally, similar slab dynamics may provide a mechanism not only for the Caribbean reorganization but also for other tectonic episodes throughout the Americas.

Abstract Image

古近纪法拉隆板块锚定驱动的加勒比板块系统构造重组
加勒比板块的构造是由其与北美板块和科科斯板块交界处向内倾的双重俯冲所决定的。这种几何形状是古近纪板块重组的结果,其中包括一个较老的俯冲系统--加勒比大弧(GAC)的废弃,以及在小安的列斯群岛(LA)弧形成期间转化为一个转换边缘。以前的模型表明,加勒比大弧和巴哈马平台沿北美被动边缘的碰撞导致了这一事件。然而,来自大安的列斯群岛的地质和地球物理约束并没有显示出与这种碰撞相对应的大规模压缩事件。我们为该地区的演变提出了一个替代模型,即法拉伦板块的下地幔渗透促进了洛杉矶俯冲的发生。我们将构造约束与地震层析成像相结合,分析了重组的时间和动态,表明洛杉矶俯冲的开始与法拉隆/科科斯板块穿透的时间相对应。通过数值俯冲模型,我们探讨了板块穿透是否构成了一套动力学上可行的机制,以启动凌空板块的俯冲。在我们的模型中,当第一块板块(法拉隆/科科斯)进入下地幔时,上板块东缘的压应力增加,第二俯冲带(LA)开始形成。由此得出的一阶板块几何形状、时间和运动学与板块重建结果比较吻合。更广泛地说,类似的板块动力学可能不仅为加勒比海重组提供了一种机制,也为整个美洲的其他构造事件提供了一种机制。
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来源期刊
Geochemistry Geophysics Geosystems
Geochemistry Geophysics Geosystems 地学-地球化学与地球物理
CiteScore
5.90
自引率
11.40%
发文量
252
审稿时长
1 months
期刊介绍: Geochemistry, Geophysics, Geosystems (G3) publishes research papers on Earth and planetary processes with a focus on understanding the Earth as a system. Observational, experimental, and theoretical investigations of the solid Earth, hydrosphere, atmosphere, biosphere, and solar system at all spatial and temporal scales are welcome. Articles should be of broad interest, and interdisciplinary approaches are encouraged. Areas of interest for this peer-reviewed journal include, but are not limited to: The physics and chemistry of the Earth, including its structure, composition, physical properties, dynamics, and evolution Principles and applications of geochemical proxies to studies of Earth history The physical properties, composition, and temporal evolution of the Earth''s major reservoirs and the coupling between them The dynamics of geochemical and biogeochemical cycles at all spatial and temporal scales Physical and cosmochemical constraints on the composition, origin, and evolution of the Earth and other terrestrial planets The chemistry and physics of solar system materials that are relevant to the formation, evolution, and current state of the Earth and the planets Advances in modeling, observation, and experimentation that are of widespread interest in the geosciences.
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