Kinematics of the South Atlantic rift
Kinematics of the South Atlantic rift
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DOI：
10.5194/se-4-215-2013
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发表时间：
2013-01-01
期刊：
影响因子：
3.4
通讯作者：
Mueller, R. D.
中科院分区：
文献类型：
--
作者：
Heine, C.;Zoethout, J.;Mueller, R. D.
南大西洋裂谷盆地是在冈瓦纳大陆西部最后裂解期间，非洲和南美洲板块之间的侏罗纪-白垩纪大型板内裂谷带的一个分支。虽然南美洲和非洲之间的相对运动的后分裂时间得到很好的解决，许多问题有关的适合重建，特别是运动学和岩石圈动力学之间的关系，在前分裂仍然不清楚，在目前公布的板块模型。我们已经编译和同化这些板内裂谷的数据，并构建了一个修正的板块运动学模型的前分裂演化的南大西洋。共轭南大西洋边缘和大陆内裂谷盆地在非洲和南美洲的结构恢复的基础上，我们实现了紧配合重建，消除了需要以前推断的大型大陆内剪切带，特别是在巴塔哥尼亚南美洲。通过定量地解释中非和西非裂谷带的地壳变形，我们已经能够间接地构建共轭西非-巴西边缘的分裂前演化的运动学历史。我们的模型表明，在大陆伸展过程中，伸展方向和速度的变化与边缘构造（如神秘的盐前凹陷盆地和圣保罗高压）的产生之间存在因果关系。我们建立了一个初始的东西向延伸南美洲和非洲（固定在今天的位置）在非常低的拉伸速度从140马，直到晚Hauterivian时代（约126马）时，裂谷活动沿着在赤道大西洋域开始显着增加。在这最初的约14百万年拉伸插曲的共轭巴西和西非边缘的盐前盆地宽度的产生。在大约126 Ma和Aptian基阶之间的中间阶段，其特征是应变局部化，赤道大西洋域岩石圈快速弱化，导致伸展速度逐渐增加，伸展方向显著向NE-SW旋转。从Aptian基阶开始，岩石圈沿沿着中南大西洋裂谷发生穿时破裂，第一个是在南大西洋最北端的塞尔希培-阿拉戈斯/穆尼河边缘部分。南美洲和非洲之间的最后解体发生在共轭桑托斯-本格拉边缘部分在113马左右，在加纳海脊和皮奥伊-塞阿拉边缘之间的赤道大西洋域在103马。我们的结论是，这样一个多速度，多方向的裂谷历史施加主要控制这些共轭被动边缘系统的演化，并可以解释一级构造结构沿着南大西洋和其他可能的被动边缘。
The South Atlantic rift basin evolved as a branch of a large Jurassic-Cretaceous intraplate rift zone between the African and South American plates during the final break-up of western Gondwana. While the relative motions between South America and Africa for post-break-up times are well resolved, many issues pertaining to the fit reconstruction and particularly the relation between kinematics and lithosphere dynamics during pre-break-up remain unclear in currently published plate models. We have compiled and assimilated data from these intraplated rifts and constructed a revised plate kinematic model for the pre-break-up evolution of the South Atlantic. Based on structural restoration of the conjugate South Atlantic margins and intracontinental rift basins in Africa and South America, we achieve a tight-fit reconstruction which eliminates the need for previously inferred large intracontinental shear zones, in particular in Patagonian South America. By quantitatively accounting for crustal deformation in the Central and West African Rift Zones, we have been able to indirectly construct the kinematic history of the pre-break-up evolution of the conjugate west African-Brazilian margins. Our model suggests a causal link between changes in extension direction and velocity during continental extension and the generation of marginal structures such as the enigmatic presalt sag basin and the Sao Paulo High. We model an initial E-W-directed extension between South America and Africa (fixed in present-day position) at very low extensional velocities from 140 Ma until late Hauterivian times (approximate to 126 Ma) when rift activity along in the equatorial Atlantic domain started to increase significantly. During this initial approximate to 14 Myrlong stretching episode the pre-salt basin width on the conjugate Brazilian and west African margins is generated. An intermediate stage between approximate to 126 Ma and base Aptian is characterised by strain localisation, rapid lithospheric weakening in the equatorial Atlantic domain, resulting in both progressively increasing extensional velocities as well as a significant rotation of the extension direction to NE-SW. From base Aptian onwards diachronous lithospheric breakup occurred along the central South Atlantic rift, first in the Sergipe-Alagoas/Rio Muni margin segment in the northernmost South Atlantic. Final break-up between South America and Africa occurred in the conjugate Santos-Benguela margin segment at around 113 Ma and in the equatorial Atlantic domain between the Ghanaian Ridge and the Piaui-Ceara margin at 103 Ma. We conclude that such a multi-velocity, multi-directional rift history exerts primary control on the evolution of these conjugate passive-margin systems and can explain the first-order tectonic structures along the South Atlantic and possibly other passive margins.