A deep seismic investigation of the Flemish Cap margin: implications for the origin of deep reflectivity and evidence for asymmetric break-up between Newfoundland and Iberia
A deep seismic investigation of the Flemish Cap margin: implications for the origin of deep reflectivity and evidence for asymmetric break-up between Newfoundland and Iberia
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DOI：
10.1111/j.1365-246x.2006.02800.x
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发表时间：
2006-03
影响因子：
2.8
通讯作者：
J. Hopper;T. Funck;B. Tucholke;K. Louden;W. Holbrook;H. Larsen
中科院分区：
文献类型：
--
作者：
J. Hopper;T. Funck;B. Tucholke;K. Louden;W. Holbrook;H. Larsen
地震反射和折射数据是沿佛兰芒帽东南缘沿着采集的，其位置与加利西亚海岸边缘的钻探和地球物理勘探相配合。数据文件的一阶不对称在纽芬兰和伊比利亚之间的最后分手。在佛兰芒帽外观察到的大陆地壳突然颈缩剖面与共轭边缘逐渐变细形成强烈对比。没有证据表明佛兰芒帽下的大陆伸展的最后阶段，导致薄的大陆地壳下面的一个强大的'S '样的反射，这表明，这种模式的扩展只发生在加利西亚银行边缘。沿着佛兰芒冰帽边缘也缺乏令人信服的证据，证明存在大面积的折返地幔带或橄榄岩脊。相反，观察到非常薄，3 - 4公里厚的海洋地壳。这个地壳是高度构造化的，并被高角度的正断层作用破碎。与拉布拉多海废弃的扩张中心相似的薄地壳和裂谷结构表明，最初的海底扩张受到当今超缓慢扩张环境中观察到的过程的影响。向陆地，佛兰芒帽的下面是一个高度反射的下地壳。反射率最有可能来自古老的古生代造山构造，是无关的伸展和裂解构造。
SUMMARY Seismic reflection and refraction data were acquired along the southeast margin of Flemish Cap at a position conjugate to drilling and geophysical surveys across the Galicia Bank margin. The data document first-order asymmetry during final break-up between Newfoundland and Iberia. An abrupt necking profile of continental crust observed off Flemish Cap contrasts strongly with gradual tapering on the conjugate margin. There is no evidence beneath Flemish Cap for a final phase of continental extension that resulted in thin continental crust underlain by a strong ‘S’-like reflection, which indicates that this mode of extension occurred only on the Galicia Bank margin. Compelling evidence for a broad zone of exhumed mantle or for peridotite ridges is also lacking along the Flemish Cap margin. Instead, anomalously thin, 3‐4-km-thick oceanic crust is observed. This crust is highly tectonized and broken up by high-angle normal faulting. The thin crust and rift structures that resemble the abandoned spreading centre in the Labrador sea suggest that initial seafloor spreading was affected by processes observed in present-day ultra-slow spreading environments. Landwards, Flemish Cap is underlain by a highly reflective lower crust. The reflectivity most likely originates from older Palaeozoic orogenic structures that are unrelated to extension and break-up tectonics.