This paper presents a three‐dimensional (3D) seismic‐based case study (∼1,200 km²) from the deepwater Niger Delta to examine the role of shale deformation in the structural development of a deepwater gravitational system. Tectono‐stratigraphic interpretation reveals that this system consists of two sets of major fold‐thrusts laterally separated by a central oblique detachment fold. A prominent shale thick beneath these structures is believed to have originated from tectonic deformation rather than a pretectonic thick, due to its complex internal structures. Seismic mapping of the growth units indicates synchronous initiation of the oblique detachment fold with the main thrusts and gradual growth in response to thickening shales. Downslope gravitational contraction is not considered the direct cause for the oblique shale‐detachment fold. Evidence from the 3D shale distribution and deformation styles within the shale unit reveals that shales that were squeezed out of adjacent shale‐thinning areas “flowed” laterally into the detachment‐fold core. Based on the spatial variation in structural deformation and growth strata distribution, this study proposes a model that considers differential contraction and differential loading from syntectonic sediments as two key factors leading to the 3D shale redistribution which ultimately determines the deformation styles and evolution history within the overburden. Additionally, seismic imaging within the shale unit recognizes various internal structures ranging from hundreds to thousands of meters in scale, and confirms what has been suggested in previous studies, that redistribution of shales occurred through a combination of multiscale brittle failures, ductile folding, and plastic flows.

中文翻译：

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页岩变形在尼日尔三角洲深水引力系统结构发展中的作用

本文提出了基于地震的三维（3D）案例研究（〜1,200 km ²）从尼日尔三角洲深水区研究页岩变形在深水重力系统结构发展中的作用。构造地层学解释表明，该系统由两组主要的褶皱冲断层组成，这些褶皱冲断层被中央斜向分离褶皱横向隔开。由于内部结构复杂，这些结构下的突出页岩厚被认为是构造变形而不是构造厚。生长单元的地震测绘表明，倾斜剥离褶皱与主推力同步开始，并随着页岩的增厚而逐渐增长。下坡重力收缩不被认为是页岩斜向分离褶皱的直接原因。页岩单元内3D页岩分布和变形样式的证据表明，从相邻页岩稀疏区挤出的页岩横向“流入”了褶皱褶皱岩心。基于结构变形和生长地层分布的空间变化，本研究提出了一个模型，该模型将构造性沉积物的差异收缩和差异载荷视为导致3D页岩重新分布的两个关键因素，最终决定了上覆岩层的变形方式和演化历史。此外，页岩单元内的地震成像可以识别数百米至数千米范围内的各种内部结构，并证实了先前研究中提出的建议，