Elevated, passive continental margins: Not rift shoulders, but expressions of episodic, post-rift burial and exhumation
Elevated, passive continental margins: Not rift shoulders, but expressions of episodic, post-rift burial and exhumation
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抬高的被动大陆边缘：不是裂肩，而是断层后偶发埋藏和折返的表现
DOI：
10.1016/j.gloplacha.2011.05.004
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发表时间：
2012
影响因子：
3.9
通讯作者：
J. Bonow
中科院分区：
文献类型：
--
作者：
P. Japsen;J. Chalmers;P. Green;J. Bonow
许多关于抬升的被动大陆边缘（EPCMs）的研究都假定，自裂谷作用和地壳分离以来，它们特有的、具有高水平高原和深切河谷的大规模形态一直存在，而裂谷后沉积物的缺乏就是非沉积的证据。然而，西格陵兰的高山暴露了千米级裂谷后沉降的证据，最近的研究表明，典型的EPCM形态与隆起的高原形成于西格陵兰。5000万年后，通过区域性裂谷后侵蚀面的抬升和切割过程，解体。由于西格陵兰边缘共享EPCMs的所有形态特征，西格陵兰的结果使我们质疑自大陆分离开始以来EPCMs一直保持较高水平的共同假设。我们目前发表的证据，裂谷后埋藏，然后从一些EPCMs及其邻近盆地的隆起和折返，以支持的概念，EPCMs不是永久的高点，他们的形态是无关的裂谷和大陆分裂。地球动力学模型将EPCM解释为自裂谷期以来的永久高点，要求在伸展地壳以下没有岩石圈地幔伸展，或有效弹性厚度> 100 km。然而，这些模型与从实际裂谷及其边缘推断的沉降历史并不一致。地球动力学模型使用低弹性厚度和岩石圈内更均匀的应变分布与早期裂谷后行为的观测结果更一致，但需要一些额外的过程来抬升边缘。我们认为，EPCMs代表背斜，岩石圈褶皱下形成的压缩地壳或岩石圈厚度的突然变化发生在盆地和裂谷盆地之间。我们认为，EPCM是表达情节后裂谷埋藏，其次是压缩引起的隆起和折返;一个情节的隆起导致该地区的侵蚀，产生一个低浮雕表面附近的水平，开放的海洋，和第二（或更多）情节（S）提高高原到目前的海拔高度，之后高原被切割河流和可能的冰川侵蚀。
Many studies of elevated, passive continental margins (EPCMs) assume that their characteristic, large-scale morphology with high-level plateaux and deeply incised valleys has persisted since rifting and crustal separation, and that the absence of post-rift sediments is evidence of non-deposition. The high mountains in West Greenland, however, expose evidence of km-scale, post-rift subsidence, and recent studies showed that typical EPCM morphology with elevated plateaux formed c. 50Myr after breakup through a process of uplift and dissection of a regional, post-rift erosion surface. Since the West Greenland margin shares all the morphological characteristics of EPCMs, the results from West Greenland lead us to question the common assumption that EPCMs have remained high since the onset of continental separation. We present published evidence of post-rift burial followed by uplift and exhumation from a number of EPCMs and their adjacent basins to support the notion that EPCMs are not permanent highs and that their morphology is unrelated to rifting and continental breakup. Geodynamic models that explain EPCMs as permanent highs since the time of rifting require either no lithospheric mantle extension below extending crust or effective elastic thicknesses >100km. Such models are, however, not consistent with the subsidence history inferred from actual rifts and their margins. Geodynamic models using low elastic thicknesses and a much more uniform distribution of strain within the lithosphere are more consistent with observations of early post-rift behaviour, but some additional process is needed to uplift the margins later. We suggest that EPCMs represent anticlinal, lithospheric folds formed under compression where an abrupt change in crustal or lithospheric thickness occurs between cratons and rift basins. We propose that EPCMs are expressions of episodes of post-rift burial followed by compression-induced uplift and exhumation; one episode of uplift results in erosion of the region to produce a low-relief surface near the level of the adjacent, opening ocean, and a second (or more) episode(s) raises the plateau to its present elevation, after which the plateau is dissected by fluvial and possibly glacial erosion.