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首页> 外文期刊>Global and planetary change >Elevated, passive continental margins: Not rift shoulders, but expressions of episodic, post-rift burial and exhumation
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Elevated, passive continental margins: Not rift shoulders, but expressions of episodic, post-rift burial and exhumation

机译：升高的被动大陆边缘：不是裂谷，而是散发，纵裂后埋葬和发掘尸体的表现

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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. 50 Myr 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 ＞ 100 km. 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.
机译：许多关于高架被动大陆边缘的研究认为，自裂谷和地壳分离以来，它们具有高台地高原和深切谷的特征性大尺度形态一直存在，并且没有裂谷后的沉积物是非裂谷的证据。沉积。然而，西格陵兰岛的高山暴露了公里级，裂谷后沉降的证据，并且最近的研究表明，典型的EPCM形态与升高的高原形成了c。破裂后通过局部裂谷后侵蚀表面的隆起和剥离过程产生的50 Myr。由于西格陵兰边缘具有EPCM的所有形态特征，因此西格陵兰的结果使我们对以下共同假设提出质疑，即自大陆分离开始以来EPCM一直保持较高水平。我们提供了一些裂痕后埋葬的证据，随后从许多EPCM及其相邻盆地中抬高并发掘出尸体，以支持以下观点：EPCM不是永久性高点，并且其形态与裂谷和大陆破裂无关。自裂谷以来，将EPCM解释为永久性高点的地球动力学模型既不需要在地壳以下延伸的岩石圈地幔延伸，也不需要有效的弹性厚度＞ 100 km。但是，这种模型与根据实际裂谷及其边界推断的沉降历史不一致。使用低弹性厚度和更均匀的岩石圈内应变分布的地球动力学模型与早期裂谷后行为的观察结果更加一致，但是以后需要增加一些额外的过程来增加边缘。我们建议，EPCM代表在挤压作用下形成的背斜，岩石圈褶皱，在克拉通和裂谷盆地之间发生地壳或岩石圈厚度的突变。我们认为，EPCM是裂痕后埋葬事件的表现，然后是压迫引起的隆起和发掘。一次隆升导致该区域受到侵蚀，从而在邻近的开放海平面附近产生低浮雕表面，而第二次（或多次）隆起将高原升至目前的高度，此后高原被河流和可能的冰川侵蚀所剖析。

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