The Iapetan rifted margin of southern Laurentia
The Iapetan rifted margin of southern Laurentia
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劳伦西亚南部的 Iapetan 裂谷边缘
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发表时间：
2011
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通讯作者：
W. A. Thomas
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作者：
W. A. Thomas
劳伦西亚南部的Iapetan裂谷边缘包括东北走向的蓝岭、沃希托和马拉松裂谷，这些裂谷被西北走向的阿拉巴马-俄克拉荷马和得克萨斯转换断层所抵消，构成了亚拉巴马和得克萨斯海岬以及沃希托和马拉松海湾的大陆边缘。对裂谷边缘的原始痕迹、构造样式和时代的解释取决于同裂谷岩石和构造的识别，以及被动边缘上的陆棚和陆棚外沉积矿床。晚古生代的瓦契塔-阿巴拉契亚外来体和造山后的南极-海湾被动边缘沉积物都覆盖了伊阿佩坦裂谷边缘，因此必须使用来自深井威尔斯和地球物理调查的数据，并沿沿着绘制暴露的瓦契塔-阿巴拉契亚逆冲带的地质图，以确定同裂谷和裂谷后岩石和构造的特征。大陆边缘和被动边缘陆棚地层主要是在下盘的沃希托外来体，然而，一些沃希托逆冲断层位移陆棚边缘基底和盖层。阿巴拉契亚逆冲断层叠瓦状的同裂谷填充的克拉通内伯明翰地堑和被动边缘架。逆冲带构造的地震恢复利用平衡剖面来确定Iapetan边缘的原始痕迹。被动边缘序列的厚度和沉降历史，以及普遍缺乏保存的同生裂谷沉积物，表明沿着亚拉巴马海角的蓝岭裂谷和沿着得克萨斯海角的沃希托裂谷存在上板块结构。德克萨斯海角的上层板块与阿根廷前心山脉的下层板块裂谷构造共轭。尽管数据有限，但马拉松海湾中沿着马拉松裂谷的被动边缘的演化表明存在下板块结构。沿着马拉松裂谷的被动边缘的演化表明存在下板块结构。地球物理模型支持陡峭的大陆边缘沿着的俄克拉何马州的转换，和类似的结构可以推断为得克萨斯州的转换。蓝岭裂谷北部的亚拉巴马海角是由同生裂谷火山岩的年龄为564马，和被动边缘海侵开始在最早的寒武纪记录沿着亚拉巴马海角和更远的北部。沃希托裂谷的年龄由转换平行克拉通内的俄克拉荷马州南部断层系统的530-539 Ma同生裂谷火山岩、阿根廷前心迪勒拉沿共轭裂谷边缘的早寒武世同生裂谷沉积物以及裂谷平行克拉通内的密西西比河谷和伯明翰地堑系统中早至晚寒武世早期的晚期同生裂谷地堑充填物记录。以及德克萨斯海角被动边缘的沉降历史。裂谷作用的历时性反映了从蓝岭裂谷到沃希托裂谷的内侧转移，沿着阿西马-俄克拉荷马转换和阿根廷前科迪勒拉裂谷从沃希托海湾。
The Iapetan rifted margin of southern Laurentia includes the northeast-striking Blue Ridge, Ouachita, and Marathon rifts, which are offset by the northwest-striking Alabama-Oklahoma and Texas transform faults, framing the Alabama and Texas promontories and the Ouachita and Marathon embayments of the continental margin. Interpretations of the original trace, structural style, and age of the rifted margin rest on identification of synrift rocks and structures, as well as continental-shelf and off-shelf sedimentary deposits on the passive margin. Both late Paleozoic Ouachita-Appalachian allochthons and post-orogenic Atlantic-Gulf passive-margin deposits cover the Iapetan rift margin, necessitating the use of data from deep wells and geophysical surveys along with geologic maps of the exposed Ouachita-Appalachian thrust belts to characterize the synrift and post-rift rocks and structures. The continental margin and passive-margin shelf strata are primarily in the footwall of the Ouachita allochthon; however, some Ouachita thrust faults displaced shelf-margin basement and cover. Appalachian thrust faults imbricate synrift fill of the intracratonic Birmingham graben and the passive-margin shelf. Palinspastic restoration of thrust-belt structures uses balanced cross sections to locate the original trace of the Iapetan margin. Thickness and subsidence history of the passive-margin successions, as well as a general lack of preserved synrift deposits, indicate an upper-plate structure along the Blue Ridge rift on the Alabama promontory and along the Ouachita rift on the Texas promontory. The upper plate on the Texas promontory is conjugate to a lower-plate rift structure on the Argentine Precordillera. Although data are limited, the evolution of the passive margin along the Marathon rift in the Marathon embayment suggests a lower-plate structure. Geophysical modeling supports a steep continental margin along the Alabama-Oklahoma transform, and a similar structure can be inferred for the Texas transform. The Blue Ridge rift north of the Alabama promontory is dated by synrift volcanic rocks as young as 564 Ma, and passive-margin transgression beginning in earliest Cambrian is documented along the Alabama promontory and farther north. The age of the Ouachita rift is documented by the 530–539 Ma synrift volcanics of the transform-parallel intracratonic Southern Oklahoma fault system, by Early Cambrian synrift sediment along the conjugate rift margin in the Argentine Precordillera, and by late synrift graben-fill of Early to early Late Cambrian age in the rift-parallel intracratonic Mississippi Valley and Birmingham graben systems, as well as by subsidence history of the passive margin on the Texas promontory. The diachroniety of rifting reflects an inboard shift from the Blue Ridge rift to the Ouachita rift along the Alabama-Oklahoma transform and rifting of the Argentine Precordillera from the Ouachita embayment.