Using borehole-constrained 3D reflection seismic data, we analyse the importance of sub-salt, salt, and supra-salt deformation in controlling the geometries and the kinematics of inverted structures in the Danish Central Graben. The Danish Central Graben is part of the failed Late Jurassic North Sea rift. Later tectonic shortening caused mild basin inversion during the Late Cretaceous and Paleogene. Where mobile Zechstein evaporites are present, they have played a significant role in the structural evolution of the Danish Central Graben since the Triassic. Within the study area, Jurassic rifting generated two major W- to SW-dipping basement faults (the Coffee Soil Fault and the Gorm–Tyra Fault) with several kilometres of normal offset and associated block rotation. The Coffee Soil Fault system delineates the eastern boundary of the rift basins, and within its hanging wall a broad zone is characterized by late Mesozoic to early Paleogene shortening and relative uplift. Buttressed growth folds in the immediate hanging wall of the Coffee Soil Fault indicate thick-skinned inversion, i.e. coupled deformation between the basement and cover units. The western boundary of the inverted zone follows the westward pinch-out of the Zechstein salt. Here, thin-skinned folds and faults sole out into Zechstein units dipping into the half-graben. The most pronounced inversion structures occur directly above and in prolongation of salt anticlines and rollers that localized shortening in the cover above. With no physical links to underlying basement faults (if present), we balance thin-skinned shortening to the sub-salt basement via a triangle zone concept. This implies that thin Zechstein units on the dipping half-graben floor formed thrust detachments during inversion while basement shortening was mainly accommodated by reactivation of the major rift faults further east. Disseminated deformation (i.e. “ductile” at seismic scales) accounts for thin-skinned shortening of the cover units where such a detachment did not develop. The observed structural styles are discussed in relation to those found in other inverted basins in the North Sea Basin and to those produced from physical model experiments. Our results indicate that Zechstein units imposed a strong control on structural styles and kinematics not only during rift-related extension but also during basin inversion in large parts of the Danish Central Graben. Reactivated thin-skinned faults soling out into thin Triassic evaporite units within the carapace above Zechstein salt structures illustrate that even thin evaporite units may contribute to defining structures during tectonic extension and shortening. We thus provide an updated and dedicated case study of post-rift basin inversion, which takes into account the mechanical heterogeneity of sub-salt basement, salt, and supra-salt cover, including multiple evaporite units of which the Zechstein is the most important.

中文翻译：

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北海丹麦中央地堑的厚皮和薄皮盆地反演——深层蒸发岩和基底运动学的作用

使用受钻孔约束的 3D 反射地震数据，我们分析了盐下、盐和盐上变形在控制丹麦中央地堑倒置结构的几何形状和运动学方面的重要性。丹麦中央地堑是晚侏罗世北海裂谷的一部分。晚白垩世和古近纪后期构造缩短导致盆地轻度反转。在存在流动的 Zechstein 蒸发岩的地方，它们在三叠纪以来丹麦中央地堑的结构演化中发挥了重要作用。在研究区内，侏罗纪裂谷产生了两条主要的 W 到 SW 倾斜的基底断层（咖啡土断层和 Gorm-Tyra 断层），具有数公里的正常偏移和相关的块旋转。咖啡土断层系统划定了裂谷盆地的东部边界，在其上盘内有一个广阔的区域，其特征是晚中生代至早古近纪缩短和相对隆升。咖啡土断层的直接上壁中的支撑生长褶皱表明厚皮反转，即基底和覆盖单元之间的耦合变形。倒置带的西边界跟随 Zechstein 盐向西的尖灭。在这里，薄皮褶皱和断层进入 Zechstein 单元，浸入半地堑。最显着的反转结构发生在盐背斜和滚柱的正上方和延伸部，这些构造使上方覆盖层局部缩短。由于与底层基底断层（如果存在）没有物理联系，我们通过三角形区域概念平衡了对盐下基底的薄皮缩短。这意味着倾斜的半地堑底板上的薄 Zechstein 单元在反转期间形成了逆冲拆离，而基底缩短主要是通过进一步向东的主要裂谷断层的重新激活来适应的。弥散变形（即地震尺度上的“延展性”）是覆盖单元薄皮缩短的原因，而没有发生这种脱离。观察到的构造样式与在北海盆地其他倒置盆地中发现的构造样式以及物理模型实验产生的构造样式相关地进行了讨论。我们的结果表明 Zechstein 单元不仅在与裂谷相关的伸展过程中而且在丹麦中央地堑大部分地区的盆地反转期间对构造样式和运动学施加了强有力的控制。重新活动的薄皮断层在 Zechstein 盐结构上方的甲壳内形成薄的三叠纪蒸发岩单元，这表明即使是薄的蒸发岩单元也可能有助于在构造伸展和缩短过程中定义结构。因此，我们提供了一个最新的、专门的裂谷后盆地反演案例研究，其中考虑了盐下基底、盐和盐上覆盖层的机械非均质性，包括多个蒸发岩单元，其中 Zechstein 是最重要的。