Late Proterozoic rifting in NW Scotland: the genesis of the ‘Torridonian’
Late Proterozoic rifting in NW Scotland: the genesis of the ‘Torridonian’
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苏格兰西北部的晚元古代裂谷：“托里登期”的起源
DOI：
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发表时间：
1982
影响因子：
2.7
通讯作者：
A. Stewart
中科院分区：
文献类型：
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作者：
A. Stewart
斯托尔群（~968 Ma）和Sleat-Torridon群（~777 Ma）这两个主要的“torridon”系列占据北北东向裂谷，切割太古宙和早元古代地壳。古水流、砾石岩相学和年代以及富粘土沉积物的初始87Sr/86Sr比值表明，这些沉积物来源于该古地壳的侧翼区域，而不是来自晚元古代的Grenville或Morarian变质岩。早期裂谷似乎大致与格伦维尔变质作用同时期，但在遗传学上与之无关。这些裂谷可能标志着一个与土卫八相关的海洋的开始，就像非常相似的三叠纪和下侏罗纪断界沉积物标志着大陆分裂的开始和现在大西洋的开始一样。这两个裂谷的西缘可能与外赫布里底逆冲带重合，而东缘可能与摩因逆冲带重合。加里东期挤压对旧裂谷边缘断裂的重新激活可能产生了摩因冲断带的下冲断，而摩因推覆本身，与阿巴拉契亚南部的下泥盆世事件类似，代表了介入的海洋关闭后形成的格伦维尔微大陆的一部分。
The two major “Torridonian” successions, viz. the Stoer Group (~968 Ma) and the Sleat–Torridon Groups (~777 Ma) occupy NNE-trending rifts cutting Archaean and early Proterozoic crust. Palaeocurrents, pebble petrography and age, and the initial 87Sr/86Sr ratios of clay-rich sediments indicate derivation from flanking areas of this old crust, rather than from late Proterozoic Grenville or Morarian metamorphic rocks. The earlier rift seems to be roughly contemporaneous with Grenville metamorphism but genetically unrelated to it. The rifts perhaps mark initiation of an Iapetus-related ocean in the same way as very similar fault-bounded Triassic and Lower Jurassic sediments mark the start of continental break-up and initiation of the present Atlantic. The western margin of both rifts probably coincides with the Outer Hebrides Thrust and the eastern margin with the Moine Thrust Zone. Reactivation of the old rift-margining faults by Caledonian compression may have generated the lower thrusts of the Moine Thrust Zone, while the Moine nappe itself, by analogy with Lower Devonian events in southern Appalachia, represents a slice of the Grenville microcontinent emplaced after closure of the intervening ocean.