The West Iberia margin is the focus of intense research since the 1980s, with some of the most exemplary geophysical cross-sections and drilling expeditions. Those data sets have been used to create conceptual models of rifting used as a template to interpret margins worldwide. We present two collocated ∼350 km long lines of multi-channel seismic (MCS) streamer data and wide-angle seismic (WAS) data collected across the Tagus Abyssal Plain (TAP). We use travel-times of first arrivals identified at WAS and reflected seismic phases identified at both WAS and MCS records to jointly invert for the P wave velocity (Vp) distribution and the geometry of a sediment unconformity, the top of the basement, and the Moho boundary. The Vp model shows that the TAP basement is more complex than previously inferred, presenting abrupt boundaries between five domains. Domain I under the foot of the slope and Domain III under the abyssal plain display Vp values and gradients of thin continental crust. In between, Domain II displays a steep Vp gradient and high Vp values at shallow depth that support that basement is made of exhumed partly serpentinized mantle. Domain IV and Domain V, further oceanward, have oceanic crust Vp structure. The new results support an unanticipated complex rift history during the initial separation of Iberia and America. We propose a geodynamic scenario characterized by two phases of extension separated by a jump of the locus of extension, caused by the northward propagation of the oceanic spreading center during the J-anomaly formation, which terminated continental rifting.

中文翻译：

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伊比利亚西部塔霍深渊平原下的裂谷与大陆-海洋过渡构造

自 1980 年代以来，西伊比利亚边缘是深入研究的重点，拥有一些最具代表性的地球物理横截面和钻探探险。这些数据集已被用于创建裂谷的概念模型，用作解释全球利润率的模板。我们展示了在塔霍深渊平原 (TAP) 上收集的两条并列 350 公里长的多道地震 (MCS) 拖缆数据和广角地震 (WAS) 数据。我们使用在 WAS 识别的初至波走时和在 WAS 和 MCS 记录识别的反射地震相位联合反演P波速度 ( V p) 分布和沉积物不整合面、基底顶部和莫霍边界。在Vp 模型显示 TAP 地下室比之前推断的更复杂，在五个域之间呈现出突然的边界。斜坡脚下的域I和深海平原下的域III显示薄大陆地壳的V p 值和梯度。在两者之间，域 II在浅层显示出陡峭的V p 梯度和高V p 值，这支持了基底是由部分蛇纹石化的地幔组成的。区域 IV 和区域 V，更远的海洋，有大洋地壳Vp 结构。新的结果支持了伊比利亚和美洲最初分离期间意想不到的复杂裂谷历史。我们提出了一个地球动力学情景，其特征是由延伸轨迹的跳跃分隔的两个延伸阶段，这是由在 J 异常形成期间海洋扩张中心向北传播引起的，这终止了大陆裂谷。