Abstract Compared to first rift phase (RP1) or single rift basins, the relationship between fault behaviours and depositional architecture during the second rift phase (RP2) remains insufficiently understood in multiphase rifts. This study attempts to provide implications for tectono-sedimentary signatures during the RP2 in multiphase rift evolution, according to an integrated analysis of 3D seismic reflections, wire logs and cores from the Lufeng Depression in the Pearl River Mouth Basin, South China Sea. The four recognised third-order sequences, ESQ1-4, define a two-stage tectono-sedimentary evolution, including an early (ESQ1-2) and a late stage (ESQ3-4) of the RP2 (38–33.8 Ma) in the Lufeng Depression. Fan-deltaic, braided deltaic sandstone-prone and lacustrine mud-prone deposits are interpreted from the basin margin towards to the central areas. During the early stage of the RP2, two relatively steep dipping E-W striking faults in the northern area were very active, undergoing rapid reactivation with a high displacement, while other faults were less active, had low displacements with respect to the extension direction and possibly represent pre-existing fault geometries. Two tectono-depositional signatures are identified during the early stage of the RP2: 1) facilitation of newly captured axially-dominated deltaic systems in the rapidly reactivated fault propagated areas, as a more uniform distribution of connected and elongated depocentres establishes an axial-supply drainage catchment; 2) sustained previous drainages from the end of the RP1 showed an increase of dip-slope sourced systems in low-displacement faulted-controlled areas, i.e. these areas lack fault-controlled topographic re-organisation but show establishment of a hanging dip-slope. The late stage of the RP2 is characterised by a low-accommodation basin as faulting activities totally waned, and thus large-sized shallow-water deltaic systems and long-distance transported sandstones are promoted. This study highlights the distinctive stratigraphic architectures and associated sediment dispersal patterns induced by progressive fault activity during the RP2 cycle. Furthermore, the proposed depositional signatures may be used as a reference when studying less data-rich multiphase rifts elsewhere.

中文翻译：

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多期裂谷中第二期裂谷的构造沉积特征：以南海珠江口盆地陆丰坳陷（38-33.9 Ma）为例

摘要 与第一裂谷相 (RP1) 或单裂谷盆地相比，第二裂谷相 (RP2) 的断层行为与沉积构造之间的关系在多相裂谷中仍未得到充分了解。根据对南海珠江口盆地陆丰坳陷的 3D 地震反射、测井和岩心的综合分析，本研究试图为多相裂谷演化中 RP2 期间的构造沉积特征提供启示。四个公认的三阶层序 ESQ1-4 定义了两阶段构造沉积演化，包括 RP2 的早期 (ESQ1-2) 和晚期 (ESQ3-4)（38-33.8 Ma）。陆丰洼地。扇三角洲，辫状三角洲砂岩和湖相泥质沉积从盆地边缘向中部地区解释。RP2早期，北部地区两条倾斜较陡的东西向断层非常活跃，重新活动迅速，位移大，而其他断层活动较少，伸展方向位移小，可能代表预先存在的断层几何形状。在 RP2 的早期阶段确定了两个构造沉积特征：1）在快速重新激活的断层传播区域促进新捕获的轴向主导的三角洲系统，因为连接和细长沉积中心的更均匀分布建立了轴向供应排水系统集水; 2) RP1 末期持续的先前排水表明低位移断控区的倾角源系统增加，即这些区域缺乏断层控制的地形重组，但显示出悬垂斜坡的建立。RP2晚期以低容陷盆地为特征，断层活动完全减弱，大型浅水三角洲体系和长距离输运砂岩发育。这项研究强调了在 RP2 循环期间由渐进断层活动引起的独特地层结构和相关的沉积物扩散模式。此外，在其他地方研究数据较少的多相裂谷时，建议的沉积特征可用作参考。