Crustal thinning in the northern Tyrrhenian Rift: Insights from multichannel and wide‐angle seismic data across the basin
Crustal thinning in the northern Tyrrhenian Rift: Insights from multichannel and wide‐angle seismic data across the basin
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第勒尼安裂谷北部地壳减薄：来自整个盆地多道和广角地震数据的见解
DOI：
10.1002/2013jb010431
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发表时间：
2014
影响因子：
--
通讯作者：
R. de Franco
中科院分区：
文献类型：
--
作者：
Moeller;I. Grevemeyer;C. R. Ranero;C. Berndt;D. Klaeschen;V. Sallares;N. Zitellini;R. de Franco
大陆岩石圈的伸展导致裂谷盆地或裂谷大陆边缘的形成。地震资料多次表明，共轭边缘具有不对称的构造结构和不同程度的拉张减薄作用。在这里，我们比较了两个一致的广角和多道地震剖面，横跨北方第勒尼裂谷系统采样地壳，经历了从北到南和从侧翼到盆地中心的不同阶段的扩展。层析成像反演显示，在科西嘉边缘和科孚岛边缘之间，地壳从~24 km均匀减薄到~17 km，意味着β因子为~1.3-1.5。在向南80公里的断面上，地壳从撒丁岛以下约24公里处减薄到坎帕尼亚边缘附近东部地区约11公里处的最大减薄（β系数约为2.2）。地壳变薄的增加伴随着上地壳中速度降低的区域，该区域逐渐向东南扩展。我们的解释是，速度降低有关的岩石破裂所造成的更高程度的脆性断层，观察到的多通道地震图像。在当地，玄武岩流成像侵入沉积物在这个区域，热流值超过100 mW/m2。整个地壳的速度范围为4.0-6.7 km/s，这是大陆岩石的典型速度，表明可能不存在与裂谷有关的岩浆底侵作用。构造前、同构造和构造后沉积单元的特征使我们能够推断活动裂谷作用的时空演化。在南部样带的西部，厚的断陷后沉积物沉积在以大型断块为界的半地堑中。随着地壳减薄程度的增加，断层间距和块体规模在东部减小。最近的构造活动表现为断层切割了东部靠近意大利大陆的海底。这两个断面显示了从北部延伸较小的裂谷（具有相当对称的共轭结构）到更南部的不对称边缘的演化。这种构造演化与东西向裂谷扩展和向南扩展速率的增加是一致的。
Extension of the continental lithosphere leads to the formation of rift basins or rifted continental margins if breakup occurs. Seismic investigations have repeatedly shown that conjugate margins have asymmetric tectonic structures and different amount of extension and crustal thinning. Here we compare two coincident wide‐angle and multichannel seismic profiles across the northern Tyrrhenian rift system sampling crust that underwent different stages of extension from north to south and from the flanks to the basin center. Tomographic inversion reveals that the crust has thinned homogeneously from ~24 km to ~17 km between the Corsica Margin and the Latium Margin implying aβfactor of ~1.3–1.5. On the transect 80 km to the south, the crust thinned from ~24 km beneath Sardinia to a maximum of ~11 km in the eastern region near the Campania Margin (βfactor of ~2.2). The increased crustal thinning is accompanied by a zone of reduced velocities in the upper crust that expands progressively toward the southeast. We interpret that the velocity reduction is related to rock fracturing caused by a higher degree of brittle faulting, as observed on multichannel seismic images. Locally, basalt flows are imaged intruding sediment in this zone, and heat flow values locally exceed 100 mW/m2. Velocities within the entire crust range 4.0–6.7 km/s, which are typical for continental rocks and indicate that significant rift‐related magmatic underplating may not be present. The characteristics of the pre‐tectonic, syn‐tectonic and post‐tectonic sedimentary units allow us to infer the spatial and temporal evolution of active rifting. In the western part of the southern transect, thick postrift sediments were deposited in half grabens that are bounded by large fault blocks. Fault spacing and block size diminish to the east as crustal thinning increases. Recent tectonic activity is expressed by faults cutting the seafloor in the east, near the mainland of Italy. The two transects show the evolution from the less extended rift in the north with a fairly symmetric conjugate structure to the asymmetric margins farther south. This structural evolution is consistent with W‐E rift propagation and southward increasing extension rates.
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影响因子：
3.7
作者：
Moeller;I. Grevemeyer;C. R. Ranero;C. Berndt;D. Klaeschen;V. Sallares;N. Zitellini;R. de Franco
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DOI：
10.1002/2013jb010527
发表时间：
2014
期刊：
Journal of Geophysical Research: Solid Earth
影响因子：
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