The passive margin of the Guiana Shield formed at the junction of the Central and Equatorial Atlantic Oceans that developed successively by a complex rifting process that achieved the final dispersal of Western Gondwana. Yet, the resulting spatial distribution of crustal thinning along the margin remains to be mapped and its controlling parameters deciphered. We used subsurface data to map the variability of crustal thinning along the margin. We show that the margin segments width primarily depends on their obliquity to rifting extension direction. The necking domain of the transform/oblique margin segments is much narrower (<100 km) than divergent segments that include hyper-extended or distal margin domains as well (200–300 km). Moreover, for a similar obliquity, the width of margin segments resulting from the Central Atlantic rifting are wider than those resulting from the Equatorial Atlantic rifting. This is primarily due to the higher obliquity and rate of the latter. Additionally, along the Central Atlantic margin segments, thinning was accommodated by lower-crustal ductile deformation, the thick syn-rift in-fill was associated with magmatism and a thicker than average oceanic crust. In contrast, the Equatorial Atlantic margin segments show little ductile deformation, reduced clastic syn-rift infill and thinner than average oceanic crust. These observations suggest that the lithosphere affected by the Central Atlantic rifting was warmer than that affected by the Equatorial Atlantic rifting. Finally, the two-step thinning in the overlapping area of the two rift systems individualized a promontory of thinned continental crust that remained as the Demerara Plateau.

中文翻译：

---

中大西洋和赤道大西洋交界处的叠加裂谷：圭亚那地盾被动边缘的形成

圭亚那地盾的被动边缘形成于中大西洋和赤道大西洋的交界处，通过复杂的裂谷过程依次发育，最终实现了冈瓦纳西部的扩散。然而，由此产生的沿边缘地壳变薄的空间分布仍有待绘制，其控制参数也有待破译。我们使用地下数据来绘制沿边缘地壳变薄的变异性。我们表明，边缘段的宽度主要取决于它们对裂谷延伸方向的倾斜度。变换/倾斜边缘段的颈缩域比包括超扩展或远端边缘域（200-300 公里）的发散段窄得多（<100 公里）。此外，对于类似的倾斜，中大西洋裂谷产生的边缘段宽度比赤道大西洋裂谷产生的边缘段宽。这主要是由于后者的倾角和速率较高。此外，沿大西洋中部边缘段，下地壳韧性变形导致变薄，厚的同裂谷填充物与岩浆作用和比平均海洋地壳更厚的地壳有关。相比之下，赤道大西洋边缘段几乎没有韧性变形，碎屑同裂隙填充减少，比平均海洋地壳更薄。这些观察结果表明，受中大西洋裂谷影响的岩石圈比受赤道大西洋裂谷影响的岩石圈温暖。最后，