Small-Scale Mantle Convection Produces Stratigraphic Sequences in Sedimentary Basins
Small-Scale Mantle Convection Produces Stratigraphic Sequences in Sedimentary Basins
复制标题
小规模地幔对流在沉积盆地中产生地层层序
作者：
K. Petersen;S. Nielsen;O. Clausen;R. Stephenson;T. Gerya
岩石的变化海平面的变化或主要的构造事件，如大陆碰撞，通过改变某些岩石类型形成的沉积环境来改变地层序列。例如，有利于石灰岩形成的深海环境可能会相对较快地转变为有利于砂岩形成的近岸环境，因为相对海平面已经下降了数米。然而，彼得森等人（第827页;见穆勒的《透视》）认为，地幔中的小规模对流也可能引起沉积物序列的明显变化。使用建模方法，他们发现这在可变时间尺度上的小规模（即几百公里）是可能的。因此，虽然沉积存款序列在区域和全球范围内的共同出现，可以使沉积岩作为海洋环境的标志，它应该记住，在表面运动的局部变化也可能表现在岩石记录。沉积地层序列可能是由小规模地幔对流引起的海平面变化造成的。旋回沉积矿床将现在地理上相距甚远但曾经属于同一沉积环境的地层序列联系起来。其中一些层序的周期为200万至2000万年，海平面升降变化或区域构造事件可能是其形成的原因。利用数值模拟，我们证明，小规模的地幔对流也可以通过经常性的本地和区域垂直表面运动的地层层序的发展。小规模的对流驱动的地层层序发生在200万至2000万年的周期，只有在几百公里的距离相关。这些结果表明，以前的层序地层分析可能包含错误的结论，关于海平面变化。
Changes in the Rocks Changing sea level or major tectonic events, such as continental collisions, shift stratigraphic sequences by changing the depositional environment where certain rock types form. For example, a deep marine environment where limestone formation is favored may shift relatively quickly to a near-shore environment favoring sandstone formation because the relative sea level has dropped several meters. Petersen et al. (p. 827; see the Perspective by Müller), however, suggest that small-scale convection in the mantle may also induce appreciable changes in the sequence of sedimentary deposits. Using a modeling approach, they found that this is possible on a small scale (that is, just a few hundreds of kilometers) over variable time scales. Thus, while the co-occurrence of sedimentary deposit sequences at regional and global scales can allow sedimentary rocks to serve as markers of marine environments, it should be kept in mind that local changes in surface movements may also manifest themselves in the rock record. Sedimentary stratigraphic sequences may result from sea-level changes that were induced by small-scale mantle convection. Cyclic sedimentary deposits link stratigraphic sequences that are now geographically distant but were once part of the same depositional environment. Some of these sequences occur at periods of 2 to 20 million years, and eustatic sea-level variations or regional tectonic events are likely causes of their formation. Using numerical modeling, we demonstrate that small-scale mantle convection can also cause the development of stratigraphic sequences through recurrent local and regional vertical surface movements. Small-scale convection-driven stratigraphic sequences occur at periods of 2 to 20 million years and correlate only at distances up to a few hundred kilometers. These results suggest that previous sequence stratigraphic analyses may contain erroneous conclusions regarding eustatic sea-level variations.