P- and S-wave velocity structure of central West Antarctica: Implications for the tectonic evolution of the West Antarctic Rift System
P- and S-wave velocity structure of central West Antarctica: Implications for the tectonic evolution of the West Antarctic Rift System
复制标题
西南极洲中部的纵波和横波速度结构：对西南极裂谷系统构造演化的启示
DOI：
10.1016/j.epsl.2020.116437
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发表时间：
2020
影响因子：
5.3
通讯作者：
Dalziel, Ian W.
中科院分区：
文献类型：
--
作者：
Lucas, Erica M.;Soto, David;Nyblade, Andrew A.;Lloyd, Andrew J.;Aster, Richard C.;Wiens, Douglas A.;O'Donnell, John Paul;Stuart, Graham W.;Wilson, Terry J.;Dalziel, Ian W.
通过对2007年至2017年在极地观测网(POLENET/ANET)和英国南极网(UKANET)记录的远震地震的相对走时进行反演而获得的西南极中部之下100~400公里深度的上地幔的新的P波和S波速度模型揭示了一个不均匀的上地幔。在马里伯德岛之下成像的低速异常(−1.0%Vp；−2.0%vs)被归因于可能来自热柱来源的热扰动上地幔，而在松岛冰川和Thwaites冰川口下成像的低速异常被解释为与裂谷有关的热结构，其中可能包括从玛丽·伯德岛流出的暖地幔。西南极裂谷系统中部的高速异常(≤0.8%Vp；1.5%Vs)表明，自晚白垩世裂谷系统形成以来，岩石圈的存在没有受到构造活动的影响。在高速度区，本特利冰下海沟部分下方的局部低速异常暗示了集中的新生代裂谷作用。模型还显示了Haag-Ellsworth Whitmore地壳块体下方的可变速度结构和瑟斯顿岛-八海岸地壳块体下方的低速度结构。西南极中部不均匀的上地幔结构表明，在小于100公里的距离内，上地幔温度可能变化100K或更多，这可能会增加固体-冰相互作用的复杂性，并影响基本冰盖条件。
New P- and S-wave velocity models of the upper mantle from 100 to 400 km depth beneath the central portions of West Antarctica, obtained by inverting relative travel-times from teleseismic earthquakes recorded on Polar Earth Observing Network (POLENET/ANET) and UK Antarctic Network (UKANET) seismic stations between 2007 and 2017, reveal a heterogeneous upper mantle. A low velocity anomaly (−1.0% Vp; −2.0% Vs) imaged beneath Marie Byrd Land is attributed to thermally perturbed upper mantle of possible plume origin, and a low velocity anomaly imaged beneath the Pine Island Glacier and the mouth of Thwaites Glacier is interpreted as a rift-related thermal structure that may include warm mantle flowing from Marie Byrd Land. High velocity anomalies (≤0.8% Vp; 1.5% Vs) imaged in the central portion of the West Antarctic Rift System indicate the presence of lithosphere unmodified by tectonic activity since the Late Cretaceous formation of the rift system. Within the region of high velocities, localized low velocity anomalies beneath parts of the Bentley Subglacial Trench are suggestive of focused Cenozoic rifting. The models also show variable velocity structure beneath the Haag-Ellsworth Whitmore crustal block and low velocities beneath the Thurston Island-Eights Coast crustal block. The heterogenous upper mantle structure of central West Antarctica indicates that upper mantle temperatures could vary by 100 K or more over distances of less than 100 km, which may add complexity to solid earth-ice interactions and influence basal ice sheet conditions.