Post break-up tectonic inversion across the southwestern cape of South Africa: New insights from apatite and zircon fission track thermochronometry
Post break-up tectonic inversion across the southwestern cape of South Africa: New insights from apatite and zircon fission track thermochronometry
复制标题
南非西南角的破碎后构造反转：磷灰石和锆石裂变径迹热测时法的新见解
DOI：
10.1016/j.tecto.2015.04.012
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发表时间：
2015
期刊：
影响因子：
2.9
通讯作者：
Wildman M
中科院分区：
文献类型：
--
作者：
Wildman M
西南非洲大陆边被认为是被动大陆边的一个例子，它是在岩石圈伸展和变薄阶段之后大陆裂谷作用形成的。最近对这一边缘的关注包括裂谷过程的理论模拟研究、开口几何形状和时间的板块运动学研究以及侧重于记录地壳结构和近海沉积记录的经验研究。在这里，我们研究了陆上地貌和构造的裂谷和断裂的反应，特别关注南非西南角。我们提出了75个新的磷灰石和8个新的锆石裂变径迹分析露头样品和陆上钻孔剖面沿着南非西缘。这些数据被用来获得强大的热历史，记录两个离散阶段的加速侵蚀冷却在早白垩世（150-130马）和晚白垩世（100-80马），分别。这两个时期的增强侵蚀的范围是区域性的，涉及公里级的侵蚀，以及目前的悬崖区的内陆延伸，虽然空间上可变的强度和风格。晚白垩世的情节也表示更局部的构造复活和反转的主要故障造成公里级的差异位移和侵蚀。新的AFT数据并不排除新生代期间发生适度地表隆起的可能性，但它们将西部边缘区域新生代侵蚀的深度限制在c以下。1公里陆上侵蚀的推断模式和年代与近海橙子和Bredasdorp盆地内的主要特征和沉积物堆积模式一致。有人建议，晚白垩世的事件是由一个组合的区域动态隆升沿着西部边缘和西南角的福克兰高原沿着福克兰-阿古拉斯断裂带的右旋位移所产生的局部构造力量。
The south-west African margin is regarded as an example of a passive continental margin formed by continental rifting following a phase of lithospheric extension and thinning. Recent attention focused on this margin has included theoretical modelling studies of rift processes, plate kinematic studies of the opening geometry and timing, and empirical studies focused on documenting the crustal structure and offshore sedimentary record. Here, we examine the onshore geomorphic and tectonic response to rifting and breakup, with a specific focus on the SW Cape of South Africa. We present 75 new apatite and 8 new zircon fission track analyses from outcrop samples and onshore borehole profiles along the western margin of South Africa. The data are used to derive robust thermal histories that record two discrete phases of accelerated erosional cooling during the Early Cretaceous (150–130 Ma) and Late Cretaceous (100–80 Ma), respectively. Both periods of enhanced erosion are regional in extent, involved km-scale erosion, and extend well inland of the current escarpment zone, albeit with spatially variable intensity and style. The Late Cretaceous episode is also expressed more locally by tectonic reactivation and inversion of major faults causing km-scale differential displacement and erosion. The new AFT data do not exclude the possibility of modest surface uplift occurring during the Cenozoic, but they restrict the depth of regional Cenozoic erosion on the western margin to less than c. 1 km. The inferred pattern and chronology of erosion onshore is consistent with the key features and sediment accumulation patterns within the offshore Orange and Bredasdorp basins. It is suggested that the Late Cretaceous event was triggered by a combination of regional dynamic uplift augmented along the western margin and in the SW Cape by local tectonic forces arising from dextral displacement of the Falkland Plateau along the Falkland–Agulhas Fracture Zone.