Internal deformation and compaction of the Makran accretionary wedge
Internal deformation and compaction of the Makran accretionary wedge
复制标题
DOI：
10.1046/j.1365-3121.1997.d01-13.x
复制
发表时间：
1997-05
期刊：
影响因子：
2.4
通讯作者：
J. Fruehn;R. S. White;T. Minshull
中科院分区：
文献类型：
--
作者：
J. Fruehn;R. S. White;T. Minshull
马克兰增生楔是地球上最大的楔之一。一个7公里厚的砂柱和石英浊积岩被纳入一系列变形的逆冲岩席中。我们提出的叠前深度偏移和聚焦误差分析（偏移速度分析）的结果上的剖面上跨马克兰楔。深度剖面显示了增生沉积物的变形方式，迁移速度使我们能够估计沉积物中的孔隙度变化。逆冲岩席显示出断层传播褶皱的证据，具有长波长的变形（约12 km）和褶皱扭折带中的次级逆冲作用，使得每个逆冲岩席的中心部分升高，形成额外的脊。这种变形方式和第一脊的15°陡表面坡度表明高度固结。根据地震偏移速度计算孔隙度，并估算了沿着剖面5个位置的流体压力与岩石静压力之比λ。与大多数增生楔中的欠压实和超压不同，沉积物输入通常在几乎整个楔中是压实的（孔隙度指数衰减）。然而，相对于正常压实曲线，孔隙度和λ在深度处略有增加，表明浊流序列可能在变形前缘的陆地方向上超压。
The Makran accretionary wedge is one of the largest on Earth. A 7‐km‐thick column of sands and quartzolithic turbidites are incorporated into this wedge in a series of deformed thrust sheets. We present the results of prestack depth migration and focusing‐error analysis (migration velocity analysis) performed on a profile across the Makran wedge. The depth section shows the deformation style of the accreted sediments, and the migration velocities allow us to estimate porosity variations in the sediments. The thrust sheets show evidence of fault‐propagation folding, with a long wavelength of deformation (≈ 12 km) and secondary thrusting in the kink bands of the folds, such that the central part of each thrust sheet is elevated to form an additional ridge. This deformation style and the 15° steep surface slope of the first ridge suggest a high degree of consolidation. Porosities were calculated from the seismic migration velocities and the ratio of fluid pressure to lithostatic pressure λ was estimated for 5 locations along the profile. Rather than being undercompacted and overpressured as in most accretionary wedges, the sedimentary input is normally compacted (exponential porosity decay) throughout almost the whole wedge. However, a slight increase in porosity and λ at depth, with respect to the normal compaction curve indicates, that the turbiditic sequence might be overpressured landward of the deformation front.