Incipient subduction at the contact with stretched continental crust: The Puysegur Trench
Incipient subduction at the contact with stretched continental crust: The Puysegur Trench
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DOI：
10.1016/j.epsl.2019.05.044
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发表时间：
2019-08-15
影响因子：
5.3
通讯作者：
Carrington, Luke
中科院分区：
文献类型：
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作者：
Gurnis, Michael;Van Avendonk, Harm;Carrington, Luke
地震贝尼奥夫带和板块运动学显示新西兰南部的皮塞古尔海沟正在向俯冲过渡。由于对当地构造及其对俯冲起始的影响知之甚少，我们利用海底地震仪和多道地震剖面进行了地震勘探。我们的早期结果表明，索兰德盆地下方压倒性的太平洋板块由块状断层和减薄的大陆地壳组成，而皮塞古尔海岭北部的内海沟壁由褶皱和断层沉积物组成。巨型逆冲断层界面已被成像并显示类似于 500 m 的下行、未受干扰的沉积物。将板块运动历史与地震速度推断密度相结合，我们发现，随着倾斜走滑板块运动将致密的海洋地壳与变薄的大陆地壳并置，板块边界上的密度差发生了变化。密度差异在 18 至 15 Ma 期间迅速增加，与俯冲起始一致，表明成分差异对俯冲起始有很大影响。 (C) 2019 Elsevier B.V. 保留所有权利。
A seismic Benioff zone and plate kinematics show Puysegur Trench south of New Zealand transitioning to subduction. Because the local structure and its influence on subduction initiation is poorly understood, we conducted a seismic survey with ocean bottom seismometers and multichannel seismic profiles. Our early results show that the overriding Pacific Plate beneath the Solander Basin is composed of block-faulted and thinned continental crust, and the inner trench wall of northern Puysegur Ridge is composed of folded and faulted sediment. The megathrust interface has been imaged and shows similar to 500 m of downgoing, undisturbed sediments. Combining plate kinematic history with seismic velocity-inferred density, we show that the density difference across the plate boundary changed as oblique strike-slip plate motion juxtaposed dense oceanic crust with thinned continental crust. The density difference rapidly increased 18 to 15 Ma, coincident with subduction initiation, suggesting that compositional differences have a large influence on subduction initiation. (C) 2019 Elsevier B.V. All rights reserved.