Oceanic transform faults and fracture zones (FZs) represent major bathymetric features that keep the records of past and present strike‐slip motion along conservative plate boundaries. Although they play an important role in ridge segmentation and evolution of the lithosphere, their structural characteristics, and their variation in space and time, are poorly understood. To address some of the unknowns, we conducted interdisciplinary geophysical studies in the equatorial Atlantic Ocean, the region where some of the most prominent transform discontinuities have been developing. Here we present the results of the data analysis in the vicinity of the Chain FZ, on the South American Plate. The crustal structure across the Chain FZ, at the contact between ∼10 and 24 Ma oceanic lithosphere, is sampled along seismic reflection and refraction profiles. We observe that the crustal thickness within and across the Chain FZ ranges from ∼4.6–5.9 km, which compares with the observations reported for slow‐slipping transform discontinuities globally. We attribute this presence of close to normal oceanic crustal thickness within FZs to the mechanism of lateral dike propagation, previously considered to be valid only in fast‐slipping environments. Furthermore, the combination of our results with other data sets enabled us to extend the observations to morphotectonic characteristics on a regional scale. Our broader view suggests that the formation of the transverse ridge is closely associated with a global plate reorientation that was also responsible for the propagation and for shaping lower‐order Mid‐Atlantic Ridge segmentation around the equator.

中文翻译：

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与链断裂带相关的地震地壳结构和地貌构造特征及其在赤道大西洋地区演化中的作用


海洋转换断层和断裂带（FZ）代表了主要的测深特征，保留了过去和现在沿保守板块边界的走滑运动记录。尽管它们在岩石圈的山脊分割和演化中发挥着重要作用，但人们对它们的结构特征及其时空变化知之甚少。为了解决一些未知问题，我们在赤道大西洋进行了跨学科地球物理研究，该地区正在发展一些最显着的变换不连续性。在这里，我们展示了南美板块链式自由区附近的数据分析结果。沿着地震反射和折射剖面对跨链 FZ 的地壳结构（位于~10 和 24 Ma 海洋岩石圈之间的接触处）进行采样。我们观察到，链 FZ 内和跨链 FZ 的地壳厚度范围为 ∼4.6–5.9 km，这与全球慢滑移变换不连续性的观测报告进行了比较。我们将自由区内接近正常海洋地壳厚度的现象归因于侧向岩脉传播机制，此前认为该机制仅在快速滑移环境中有效。此外，我们的结果与其他数据集的结合使我们能够将观测扩展到区域尺度的形态构造特征。我们更广泛的观点表明，横脊的形成与全球板块重新定向密切相关，全球板块重新定向也负责传播和塑造赤道周围的低阶大西洋中脊分割。