Deep crustal structure of Bransfield Strait: Initiation of a back arc basin by rift reactivation and propagation
Deep crustal structure of Bransfield Strait: Initiation of a back arc basin by rift reactivation and propagation
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DOI：
10.1029/2003jb002468
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发表时间：
2003-10
影响因子：
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通讯作者：
G. Christeson;D. Barker;J. Austin;I. Dalziel
中科院分区：
文献类型：
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作者：
G. Christeson;D. Barker;J. Austin;I. Dalziel
[1]我们提出了一个广角地震调查的结果，包括一个网格的五个走向和三个倾角的配置文件，在南极洲布兰斯菲尔德海峡进行。我们使用了二维地震层析成像和射线追踪相结合，以约束该地区的速度结构。最薄的地壳位于解释的新火山区，但地壳厚度为10-15公里，表明裂谷作用尚未发展到形成正常的洋壳。地壳沿南设得兰群岛基底沿着20-26 km，沿南极半岛边缘沿着14-20 km。沿走向，地壳一般由NE向SW增厚。地壳减薄的范围在东北部比西南部更广，所观察到的地壳厚度模式与从东北向西南的伸展传播相一致。上地幔速度为7.45 ± 0.2 km/s，S表明存在少量的部分熔融或正常的上地幔各向异性，慢方向平行于裂谷轴。沿半岛边缘上地壳速度沿着的大的横向变化与地震成像的构造边界相对应。这些构造边界与现今新火山带内观察到的大速度变化或形态步骤之间没有相关性。我们认为，裂谷地形现在的特点南极半岛边缘形成之前形成的现代盆地。
[1] We present the results of a wide-angle seismic survey, consisting of a grid of five strike and three dip profiles, conducted in Bransfield Strait, Antarctica. We used a combination of two-dimensional seismic tomography and ray tracing to constrain velocity structure in the region. Thinnest crust is located within the interpreted neovolcanic zone, but the crustal thickness of 10–15 km indicates that rifting has not progressed to the formation of normal oceanic crust. Crust thickens to 20–26 km along the South Shetland Islands pedestal and to 14–20 km along the Antarctic Peninsula margin. Along-strike, crust generally thickens from the NE to the SW. In the across-strike direction, crustal thinning is observed over a broader area in the NE than in the SW. The observed crustal thickness pattern is consistent with propagation of extension from the NE toward the SW. Upper mantle velocities of 7.45 ± 0.2 km/s indicate either the presence of a small amount of partial melt or normal upper mantle anisotropy with the slow direction parallel to the rift axis. Large lateral changes in upper crustal velocities along the Antarctic Peninsula margin correspond with seismically imaged structural boundaries. There is no correlation between these structural boundaries and large velocity changes or morphologic steps observed within the present-day neovolcanic zone. We suggest that the rift topography now characterizing the Antarctic Peninsula margin formed prior to the formation of the modern basin.