How much systems-tract scale, three-dimensional stratigraphic variability is present insequence stratigraphy?: An answer from middle Miocene Pearl River Mouth Basin
How much systems-tract scale, three-dimensional stratigraphic variability is present insequence stratigraphy?: An answer from middle Miocene Pearl River Mouth Basin
复制标题
层序地层学中存在多少体系域尺度、三维地层变异性？：来自中新世珠江口盆地的回答
作者：
Shaohua Xu;Jianhui Han;Yingmin Wang;Min He;Xiong Pang;Weitao Chen;Chenglin Gong;Chunyu Qin;Xiaogang Li;Shang Xu
以往的层序地层学方法主要采用二维叠加模式来重建地层格架。层序地层学的未来将更加关注体系域尺度和三维地层变异性。利用1.2 · 104 km ~ 2（4.63 · 103 mi ~ 2）的三维地震资料，结合区域二维地震测线和21个钻孔，研究了14.8-13.8 Ma珠江陆架边缘至深水沉积棱柱体的体系域尺度和三维地层变异性。将研究区棱柱体划分为4个主要的体系域，即高位体系域（HST）、下降期体系域（FSST）、低位体系域（LST）和海侵体系域（TST）。每个体系域都由一个给定的斜形结构和叠加样式表示：（1）具有加积到加积的斜积层组是HST，（2）具有加积到退化（PD）的斜积层组是FST，（3）具有加积到加积（PA）的斜积层组是LST，（4）具有退积的斜积层组是TST、LST或HST。此外，珠江FSST和LST显示下倾地层变异性，在区域上至少表现在三个方面：（1）陆棚边缘三角洲连接下倾到盆底扇，（2）陆棚边缘三角洲连接下倾而无扇，（3）盆底扇连接上倾而无三角洲。在沿走向方向上，珠江FSST可以表现出低角度叠加，而不仅仅是PD叠加。LST可以呈现退积堆积，而不仅仅是PA堆积。因此，在分配给定体系域时，重新强调体系域的物理位置。在此基础上，对三个体系域的概念进行了年代地层学意义上的修正。低位体系域是层序的最低体系域，以海岸线的正常海退为特征，横向上包括同生地层单元。高水位体系域是层序的上部体系域，以海岸线的正常海退作为其诊断特征，并在横向上包括同生地层单元。TST是一个层序的中间体系域，产生海岸线的后退，并排除LST和HST的横向上的同期超覆单元。FSST未修订，因为FSST可能是独立于供应的特性。
Prior sequence stratigraphic methods mainly employed twodimensional (2-D) stacking patterns to reconstruct stratigraphic frameworks. The future of sequence stratigraphy will pay more attention to systems-tracts scale and three-dimensional (3-D) stratigraphic variability. Using 1.2 · 104 km2 (4.63 · 103 mi2) 3-D seismic data, tied to regional 2-D seismic lines and 21 boreholes, the present study examines systems-tract scale and 3-D stratigraphic variability of the 14.8–13.8 Ma Pearl River shelfmargin to deep-water sedimentary prisms. The studied prisms were divided into four main systems tracts, namely, highstand systems tract (HST), falling-stage systems tract (FSST), lowstand systems tract (LST), and transgressive systems tract (TST). Each systems tract is represented by a given clinoformal architecture and stacking pattern: (1) clinothem sets with aggradation to progradation are HST, (2) clinothem sets with progradation to degradation (PD) are FSST, (3) clinothem sets with progradation to aggradation (PA) are LST, and (4) clinothem sets with retrogradation are TST, LST, or HST. In addition, Pearl River FSST and LST display downdip stratigraphic variabilities which are regionally manifested in at least three ways: (1) shelf-edge deltas linked downdip to basin-floor fans, (2) shelf-edge deltas linked downdip without fans, and (3) basin-floor fans linked updip that lack deltas. In along-strike orientation, the Pearl River FSST could exhibit low-angle progradation, not just PD stacking. The LST could present retrogradational stacking, not just PA stacking. Therefore, the physical position of a systems tract is reemphasized in terms of assigning a given systems tract. The concepts of three systems tracts are then revised for chronostratigraphic significance. The LST is the lowermost systems tract of a sequence, presenting a normal regression of the shoreline as its diagnostic characteristic and including contemporaneous stratigraphic units laterally. The HST is the upper systems tract of a sequence, providing a normal regression of the shoreline as its diagnostic characteristic and including contemporaneous stratigraphic units laterally. The TST is the middle systems tract of a sequence, generating a backstep of the shoreline and excluding contemporaneous onlapping units of both the LST and HST laterally. The FSST has not been revised because FSST may be a supply-independent feature.