Management of ambiguities in magnetostratigraphic correlation
Management of ambiguities in magnetostratigraphic correlation
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DOI：
10.1016/j.epsl.2013.04.019
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发表时间：
2013-06
影响因子：
5.3
通讯作者：
F. Lallier;Christophe Antoine;J. Charreau;G. Caumon;J. Ruiu
中科院分区：
文献类型：
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作者：
F. Lallier;Christophe Antoine;J. Charreau;G. Caumon;J. Ruiu
磁性地层学是一种强有力的工具，可以提供沉积物的绝对定年，从而实现可靠而详细的年代地层对比。它的依据是在某一沉积物剖面中观察和测量的磁极柱与磁极参考标度之间的相互关系，而磁极参考标度通过其他独立方法确定了极性变化的日期。然而，磁性地层的对比是松散的，因为它们只受到二元磁性时（即正常或反转）及其厚度的约束，这两者都是根据磁性反射方向的深度变化来定义的。一个给定的磁极性区域的厚度是时间和沉积物积累速率的函数，这可能不是固定的，导致在执行相关性时的模糊性。为了解决这些模糊性，提出了一种基于动态时间弯曲算法的数值方法。计算磁性地层对比，以尽量减少当地的变化的积累率。所提出的方法的主要优点是自动提供一组合理可能的相关性。然后可以仔细检查这组数据，以进行进一步的分析和解释。然而，相关性的可能性应谨慎处理，因为它取决于磁性地层剖面本身的信息内容，并通过辅助约束最终保持有效。然而，该方法给出了一致的结果，模拟突然变化的沉积速率的困难的合成情况下。还提供了由以前的作者辩论的真实部分的见解。
Magnetostratigraphy is a powerful tool to provide absolute dating of sediments enabling robust and detailed chronostratigraphic correlations. It is based on the correlation of a magnetic polarity column, observed and measured in a given sediment section, to a magnetic polarity reference scale where polarity changes are well dated via other independent methods. However, magnetostratigraphic correlations are loose as they are only constrained by binary magnetic chrons (i.e. normal or reversal) and their thickness, which are both defined from depth variations of the magnetic remanent directions. The thickness of a given magnetic polarity zone is a function of time and sediment accumulation rate, which may not be stationary, leading to ambiguities when performing the correlations. To address these ambiguities, a numerical method based on the Dynamic Time Warping algorithm is proposed. Magnetostratigraphic correlations are computed in order to minimise the local variation of the accumulation rate. The main advantage of the proposed method is to automatically provide a set of reasonably likely correlations. This set can then be scrutinised for further analysis and interpretation. However, the likelihood of a correlation should be handled carefully as it depends on the information content of the magnetostratigraphic section itself and remain ultimately valid by ancillary constraint. Nevertheless, the method gives consistent results on difficult synthetic cases that simulate abrupt variations of the sedimentation rate. Insights on true sections debated by previous authors are also given.