Lateral variation of sequence stratigraphic architecture on passive continental margin and its enlightenment: A case from the Middle Miocene in Pearl River Mouth Basin in 13.8 Ma

Xu Shaohua; He Min; Pang Xiong; Chen Weitao; Wang Yingmin; Zhuo Haiteng; Qin Chunyu

doi:10.11743/ogg20180418

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Lateral variation of sequence stratigraphic architecture on passive continental margin and its enlightenment: A case from the Middle Miocene in Pearl River Mouth Basin in 13.8 Ma
Vol. 39, Issue 4, Pages: 811-822(2018)
Online First：28 August 2018，

Published：2018
DOI： 10.11743/ogg20180418
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DOI：

Xu Shaohua, He Min, Pang Xiong, et al. Lateral variation of sequence stratigraphic architecture on passive continental margin and its enlightenment: A case from the Middle Miocene in Pearl River Mouth Basin in 13.8 Ma[J]. 2018, 39(4): 811-822. DOI： 10.11743/ogg20180418.

摘要

当前层序地层格架的建立依据大多源自于河口附近地层叠置规律的分析，而忽略了地层叠置关系在沉积体侧向上的变化，以至于体系域的划分标准受到沉积体范围的限制，使得层序地层划分方案不具有唯一性，难以开展凹陷内更大范围的地层对比。以珠江口盆地中中新世13.8 Ma的陆坡为例，利用井-震综合分析的方法，详细阐述层序边界（SB）特征、下降体系域（FSST）及低位体系域（LST）的地层叠置样式在侧向上的变化。认为与LST进积体系地震上可侧向追踪对比的一系列上超地层应命名为LST，而不是TST。基于区域等时对比的原则，将LST定义修订为形成于基准面上升早期，以可容空间增加速率小于沉积物供给速率为相标志，同时包含侧向上与之等时对比的一套地层；将HST定义修订为形成于基准面上升晚期，以可容空间增加速率小于沉积物供给速率为相标志，同时包含侧向上与之等时对比的一套地层；将TST定义为可容空间增加速率大于沉积物供给速率，同时排除侧向上与LST和HST等时对比的两套地层。建议被动陆缘层序地层格架的建立方法应以河口、陆架和深水作为一个有机整体，寻找各体系域的“唯一性”相标志，开展三维空间上的系统对比和检验，而非人为的对一个沉积体系分块建立层序地层格架。

Abstract

Current construction of sequence stratigraphic framework is mainly based on the analysis of stratigraphic superposition patterns near the estuary

with their lateral variation in the sedimentary body neglected.So the division standards of system tracts are restricted by the range of sedimentary bodies

and the sequence stratigraphic division scheme is not unique.As a result

it's difficult to carry out stratigraphic correlation in a larger scope in a sag. The study took a case of Pearl River Mouth Basin clinoform in 13.8 Ma(belongs to the Middle Miocene)

and elaborated the characteristics of sequence boundary(SB)

and the lateral variations of stratigraphic superposition patterns in Falling Stage System Tract(FSST)and Low stand System Tract (LST)

through combination analysis of well and seismic data.The results show that a series of onlapping strata

which can be laterally tracked and correlated with LST progradation systems on seismic sections

should be named as LST rather than TST.Based on the principle of regional isochronous correlation

the definition of LST should be revised as a set of strata that are developed in the early of base-level rising cycle

marked by accommodation increasing rate being lower than the sediment supply rate

and contain lateral equivalent beds.While the definition of HST is revised as a set of strata that are formed in the late of base-level rising cycle

marked by the accommodation increasing rate being less than the sediment supply rate

and include a set of lateral equivalent beds. Meanwhile

the TST is defined as a set of strata with facies marker of the accommodation increasing rate being greater than the sediment supply rate and the lateral equivalents of LST and HST being excluded.Thus we proposed that the reconstruction of sequence stratigraphy framework should take estuary

shelf and deep water as an integrated whole

looking for the unique facies marker of each system tract

and carrying out systematic comparison and checking in three-dimensional space

rather than factitiously splitting a sedimentary system and then establish sequence stratigraphic frameworks separately.