Abstract Globally, oceanic crust has relatively uniform thickness and structure compared to continental crust, with typical ocean crust being ~5–8 km thick. However, a substantial proportion of oceanic crust is thickened outside the normal range in the form of oceanic plateaus and crust affected by hotspots. The Rio Grande Rise (RGR) is the most prominent bathymetric feature in the western South Atlantic Ocean, and was thickened by activity of the Tristan hotspot. We use multichannel seismic data collected along the eastern margin of the RGR to investigate the relationship history between the thickened crust of the RGR and the adjacent normal crust. We find numerous normal faults spatially coincident with the region where oceanic crust begins to thicken from normal to RGR crust. Using crosscutting relationships and superposition, our interpretation supports protracted extensional deformation at the eastern margin of the RGR, including recent activity that appears to deform the modern seafloor. We attribute the faulting to differential subsidence linked to crustal thickness variations between the thickened RGR and ‘normal’ oceanic crust. Given the fundamental processes we attribute to the cause of faulting and the proportion of thickened oceanic crust globally, it is possible that regions of many oceanic plates experience intraplate deformation after formation.

中文翻译：

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南大西洋里奥格兰德海隆附近洋壳的板内变形

摘要 在全球范围内，与大陆地壳相比，大洋地壳的厚度和结构相对均匀，典型的大洋地壳厚度约为5-8 km。然而，相当一部分大洋地壳以受热点影响的大洋高原和地壳的形式在正常范围之外增厚。格兰德河海隆 (RGR) 是南大西洋西部最突出的水深特征，并因特里斯坦热点的活动而增厚。我们利用沿 RGR 东缘采集的多道地震资料研究了 RGR 加厚地壳与相邻正常地壳之间的关系历史。我们发现许多正断层在空间上与大洋地壳开始从正常地壳增厚到 RGR 地壳的区域重合。使用横切关系和叠加，我们的解释支持 RGR 东部边缘的长期伸展变形，包括最近似乎使现代海底变形的活动。我们将断层归因于与加厚的 RGR 和“正常”大洋地壳之间地壳厚度变化相关的差异沉降。鉴于我们归因于断层原因和全球加厚洋壳的比例的基本过程，许多大洋板块的区域有可能在形成后经历板内变形。