The age of the Springdale Group, western Newfoundland, and correlative rocks—evidence for a Llandovery overlap assemblage in the Canadian Appalachians
The age of the Springdale Group, western Newfoundland, and correlative rocks—evidence for a Llandovery overlap assemblage in the Canadian Appalachians
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纽芬兰西部斯普林代尔群和相关岩石的年龄——加拿大阿巴拉契亚山脉兰多弗里重叠组合的证据
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发表时间：
1987
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影响因子：
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通讯作者：
K. Currie
中科院分区：
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作者：
F. W. Chandler;R. Sullivan;K. Currie
摘要斯普林代尔群（一个双峰火山岩和红层序列）长英质火山岩的锆石年龄为429 + 6，−5 Ma，确定了该群的Llandovery年龄。纽芬兰的Dunnage和亨伯区的其他地区的类似序列也给出了Llandovery化石或放射性年龄，表明了这些区域中岩性相似序列之间的时间相关性。在新斯科舍省的阿瓦隆和梅古马地区，双峰式陆上流纹岩和玄武岩的独特序列以及相关的陆上至浅海沉积岩给出了化石或放射性年龄，可以证明或可以说非常接近斯普林代尔群的年龄。这些序列表明，重叠组合固定的阿瓦隆和Meguma区的最低年龄的增生到北美。该组合的时代、岩浆和沉积特征与陆壳成因一致，表明土卫八洋在早志留世之前就已关闭。如果这些考虑是正确的，那么泥盆纪的西印度造山运动必然涉及到土卫八海洋关闭之后的热力和机械的再调整，或者是一个完全独立的板块运动事件。
ABSTRACT A zircon age of 429 + 6, −5 Ma on felsic volcanic rocks of the Springdale Group, a sequence of bimodal volcanic rocks and redbeds, establishes a Llandovery age for this group. Similar sequences from other parts of the Dunnage and Humber zones of Newfoundland also give Llandovery fossil or radiometric ages, demonstrating temporal correlation among lithologically similar sequences in these zones. Distinctive sequences of bimodal, subaerial rhyolite and basalt with associated subaerial to shallow marine sedimentary rocks within the Avalon and Meguma zones of Nova Scotia give fossil or radiometric ages demonstrably or arguably very close to the age of the Springdale Group. These sequences suggest an overlap assemblage fixing the minimum age of accretion of the Avalon and Meguma zones to North America. The age and the magmatic and sedimentary character of the assemblage are compatible with origin on or from continental crust, implying that the Iapetus ocean was closed prior to Early Silurian time. If these considerations are correct, the Devonian Acadian orogeny must involve either thermal and mechanical readjustments subsequent to the closing of the Iapetus ocean, or a completely separate episode of plate motion.