Parasequences: Allostratigraphic misfits in sequence stratigraphy
Parasequences: Allostratigraphic misfits in sequence stratigraphy
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准层序：层序地层学中的异地层错位
DOI：
10.1016/j.earscirev.2020.103289
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发表时间：
2020
影响因子：
12.1
通讯作者：
M. Zecchin
中科院分区：
文献类型：
--
作者：
O. Catuneanu;M. Zecchin
在低分辨率地震地层学背景下，准层序被引入作为地震尺度系统域的构建块。这一概念的缺陷与准层序边界的定义有关，即标志着水体突然加深的岩性不连续性。就这一一般含义而言，“洪水面”可能是海侵沉积物内的相接触，或者可能与不同类型的层序地层表面（最大海退、海侵沟壑或最大洪水）一致。在所有情况下，洪水表面都是仅限于沿海和浅水环境的异地层接触，可以证明水突然加深的证据。浅水系统也可能不存在洪水表面，在水逐渐加深的过程中，顺应层序不断积累。由此可见，(1) 准层序的范围小于体系域，(2) 体系域并不总是由堆积的准层序组成。这些限制阻碍了准层序概念在层序地层学中的可靠使用。高分辨率层序地层学的进展表明，层序和准层序的规模并不相互排斥；这两种类型的单位定义了在高分辨率尺度上描绘地层旋回的不同方法。在准层序尺度上发育的层序为沿海和浅水环境内外的相关性提供了更可靠的替代方案，从而使准层序变得过时。形成洪水面的每次海侵都从最大海退面开始，并以在海侵规模下观察到的最大洪水面结束。这些系统域边界总是比海侵期间可能形成的任何相接触更广泛。洪水面仍然与相关系的描述相关，但其地层意义需要根据具体情况进行评估。高分辨率研究中层序和体系域的使用提供了所有地层尺度的方法和命名的一致性，无论地质环境以及可用数据的类型和分辨率如何。
Parasequences were introduced as the building blocks of seismic-scale systems tracts in the context of low-resolution seismic stratigraphy. Pitfalls of this concept relate to the definition of parasequence boundaries as lithological discontinuities that mark episodes of abrupt water deepening. With this general meaning, ‘flooding surfaces’ may be facies contacts within transgressive deposits, or may coincide with different types of sequence stratigraphic surfaces (maximum regressive, transgressive ravinement, or maximum flooding). In all cases, flooding surfaces are allostratigraphic contacts restricted to coastal and shallow-water settings, where evidence of abrupt water deepening can be demonstrated. Flooding surfaces may also be absent from the shallow-water systems, where conformable successions accumulate during gradual water deepening. It follows that (1) parasequences have smaller extent than systems tracts, and (2) systems tracts do not always consist of stacked parasequences. These limitations prevent the dependable use of the parasequence concept in sequence stratigraphy.Advances in high-resolution sequence stratigraphy show that the scales of sequences and parasequences are not mutually exclusive; the two types of units define different approaches to the delineation of stratigraphic cycles at high-resolution scales. Sequences that develop at parasequence scales provide a more reliable alternative for correlation, both within and outside of the coastal and shallow-water settings, rendering parasequences obsolete. Every transgression that affords the formation of a flooding surface starts from a maximum regressive surface and ends with a maximum flooding surface observed at the scale of that transgression. These systems tract boundaries are invariably more extensive than any facies contacts that may form during the transgression. Flooding surfaces remain relevant to the description of facies relationships, but their stratigraphic meaning needs to be assessed on a case-by-case basis. The use of sequences and systems tracts in high-resolution studies provides consistency in methodology and nomenclature at all stratigraphic scales, irrespective of geological setting and the types and resolution of the data available.
影响因子：
12.1
作者：
Colombera L
通讯作者：
Colombera L