Abstract Although climate proxy (δ18O) across the world ocean basins reveals that orbital forcing significantly controlled the Pliocene and the Pleistocene sediment deposition, and has been demonstrated in seismic and outcrop studies on the continental shelves of many margins, few or no seismic stratigraphic studies have investigated orbital forcing on deep-water sediment records. In this study, we combined detailed seismic stratigraphy and 3D geomorphological analysis of a high-resolution 3D seismic block in a detailed study of the stratigraphic evolution of the western Niger Delta intraslope basins over the last 5.5 Ma. Two mega seismic units named MSU 1 and MSU 2 were identified. The change in sedimentary architecture from (i) mass flows and turbidite sequences to (ii) hemipelagic and turbidite sequences at the MSU 1/MSU 2 transition coincides with a significant (x3) increase in sedimentation rates and a transition from dominant 400 ka eccentricity cycles (from 5.3 Ma-0.8 Ma) to dominant 100 ka eccentricity cycles, at the Middle Pleistocene Transition (MPT) (circa 0.8‐–0 Ma). The timing of these changes was estimated based on a detailed analysis of seismic facies succession, correlation of seismic markers with high-resolution sea-level and oxygen isotope curves, and estimation of sequence duration. Further changes in the sedimentary record, characterised by turbidite-dominated sequences at the lower part of MSU 1 to mixed mass flows and turbidite sequences at the upper part of MSU 1, were respectively correlated with changes that occurred in the early Pliocene (circa 4.9 Ma) and in the early Pleistocene (circa 2.6 Ma). The depositional sequence on the western Niger Delta intraslope basin is usually characterised by a falling stage erosional surface (FSES) at its base and top (sequence boundary), and by (i) basal MTDs/bypass facies (where preserved), (ii) turbidite feeder channels/aggrading or meandering channel levee complexes and/or MTDs (slides/slumps) and (iii) hemipelagic drapes that successively document the falling stage, lowstand to early transgressive and late transgressive to highstand transits of the shoreline. The Pliocene and Pleistocene sedimentary records of the western Niger Delta intraslope basins were controlled by interplay between allocyclic forcing linked to glacio-eustatic sea-level oscillations and basin tectonics associated with mobile shale movements. .

中文翻译：

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尼日尔三角洲西部斜坡内盆地的上新世和更新世地层演化：冰川-海平面和盆地构造强迫的记录

摘要 尽管全球海洋盆地的气候代理（δ18O）表明轨道强迫显着控制了上新世和更新世沉积物沉积，并且在许多边缘大陆架的地震和露头研究中得到了证明，但很少或没有地震地层学研究研究了对深水沉积物记录的轨道强迫。在这项研究中，我们结合了高分辨率 3D 地震块的详细地震地层学和 3D 地貌分析，详细研究了过去 5.5 Ma 中尼日尔三角洲西部斜坡内盆地的地层演化。确定了两个名为 MSU 1 和 MSU 2 的巨型地震单元。在 MSU 1/MSU 2 过渡处，沉积结构从 (i) 质量流和浊积岩层序到 (ii) 半远洋和浊积岩层序的变化与沉积速率的显着 (x3) 增加和从占主导地位的 400 ka 偏心率循环的转变相吻合（从 5.3 Ma-0.8 Ma）到主要的 100 ka 偏心率循环，在中更新世过渡（MPT）（大约 0.8--0 Ma）。这些变化的时间是根据对地震相序列的详细分析、地震标记与高分辨率海平面和氧同位素曲线的相关性以及序列持续时间的估计来估计的。沉积记录的进一步变化，以MSU 1下部的浊流为主的层序到MSU 1上部的混合质量流和浊流层序为特征，分别与上新世早期（约 4.9 Ma）和更新世早期（约 2.6 Ma）发生的变化相关。尼日尔三角洲西部斜坡内盆地的沉积层序通常以底部和顶部（层序边界）的下降阶段侵蚀面 (FSES) 为特征，以及 (i) 基底 MTD/旁路相（在保留的情况下），（ii）浊流支流通道/加积或蜿蜒的通道堤坝复合体和/或 MTD（滑坡/坍塌）和 (iii) 半远洋披覆，连续记录了海岸线的下降阶段、低位到早期海侵和晚期海侵到高水位过境。尼日尔三角洲西部斜坡内盆地的上新世和更新世沉积记录受与冰川 - 静海平面振荡相关的异循环强迫和与移动页岩运动相关的盆地构造之间的相互作用控制。.