Heterogeneous upper mantle structure beneath the Ross Sea Embayment and Marie Byrd Land, West Antarctica, revealed by P-wave tomography
Heterogeneous upper mantle structure beneath the Ross Sea Embayment and Marie Byrd Land, West Antarctica, revealed by P-wave tomography
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DOI：
10.1016/j.epsl.2019.02.013
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发表时间：
2019-05
影响因子：
5.3
通讯作者：
A. White-Gaynor;A. Nyblade;R. Aster;D. Wiens;P. Bromirski;P. Gerstoft;R. Stephen;S. Hansen;T. Wilson;I. Dalziel;A. Huerta;J. Paul Winberry;S. Anandakrishnan
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作者：
A. White-Gaynor;A. Nyblade;R. Aster;D. Wiens;P. Bromirski;P. Gerstoft;R. Stephen;S. Hansen;T. Wilson;I. Dalziel;A. Huerta;J. Paul Winberry;S. Anandakrishnan
我们提出了一个上地幔P波速度模型的罗斯海海湾（RSE）地区的西南极洲，通过反演的相对P波走时记录的1881年10月地震的两个临时宽带地震仪部署在罗斯冰架，以及区域冰和岩石周围的RSE地震台站。更快的上地幔P波速度（100 + 1%）的RSE东部的特点，这表明在这一部分的RSE的岩石圈可能没有被重新加热的中至晚新生代裂谷，影响其他部分的晚白垩世西南极裂谷系。较低的上地幔速度（100 - 1%）是RSE西部约1500 km宽区域的特征，从RSE中部延伸到横贯南极山脉（TAM）。在这个区域内，模型显示了两个速度更慢的区域（1.5%），中心位于Mt.埃里伯斯山墨尔本沿着TAM前线。我们的属性更广泛的地区的慢速度主要是重新加热的岩石圈地幔的古近纪裂谷，而最近的火山活动的地区下面的速度较慢，可能反映了一个新生代本阶段的裂谷和/或羽活动与恐怖裂谷的形成。在玛丽伯德地西部的福特山脉和爱德华七世半岛下面，P波模型显示，在几百公里的距离上，上地幔速度的横向变化为±0.5%。假设地幔成分没有显著变化，在RSE和玛丽伯德地西部下方成像的上地幔速度的不均匀性表明上地幔温度至少有100° C的变化。这些温度变化可能导致整个研究区的地表热流和地幔粘度在区域范围内的差异为100 ±10 mW/m2和102 Pa·s，可能通过影响基底冰条件和冰川均衡调整来影响西南极冰盖的稳定性。
We present an upper mantle P-wave velocity model for the Ross Sea Embayment (RSE) region of West Antarctica, constructed by inverting relative P-wave travel-times from 1881 teleseismic earthquakes recorded by two temporary broadband seismograph deployments on the Ross Ice Shelf, as well as by regional ice-and rock-sited seismic stations surrounding the RSE. Faster upper mantle P-wave velocities (∼+ 1%) characterize the eastern part of the RSE, indicating that the lithosphere in this part of the RSE may not have been reheated by mid-to-late Cenozoic rifting that affected other parts of the Late Cretaceous West Antarctic Rift System. Slower upper mantle velocities (∼− 1%) characterize the western part of the RSE over a∼ 500 km-wide region, extending from the central RSE to the Transantarctic Mountains (TAM). Within this region, the model shows two areas of even slower velocities (∼− 1.5%) centered beneath Mt. Erebus and Mt. Melbourne along the TAM front. We attribute the broader region of slow velocities mainly to reheating of the lithospheric mantle by Paleogene rifting, while the slower velocities beneath the areas of recent volcanism may reflect a Neogene-present phase of rifting and/or plume activity associated with the formation of the Terror Rift. Beneath the Ford Ranges and King Edward VII Peninsula in western Marie Byrd Land, the P-wave model shows lateral variability in upper mantle velocities of±0.5% over distances of a few hundred km. The heterogeneity in upper mantle velocities imaged beneath the RSE and western Marie Byrd Land, assuming no significant variation in mantle composition, indicates variations in upper mantle temperatures of at least 100° C. These temperature variations could lead to differences in surface heat flow of∼±10 mW/m 2 and mantle viscosity of 10 2 Pa s regionally across the study area, possibly influencing the stability of the West Antarctic Ice Sheet by affecting basal ice conditions and glacial isostatic adjustment.