Age determination of the Lower Watrous red-beds of the Williston Basin, Saskatchewan, Canada
Age determination of the Lower Watrous red-beds of the Williston Basin, Saskatchewan, Canada
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加拿大萨斯喀彻温省威利斯顿盆地下沃特勒斯红层的年龄测定
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发表时间：
2012
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通讯作者：
P. Dennis
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作者：
Gemma S. Butcher;A. Kendall;A. Boyce;I. Millar;J. Andrews;P. Dennis
下沃特罗斯红层是威利斯顿盆地的油气藏所在地，沿着与马尼托巴（下阿马兰斯组）和美国（斯皮尔菲什组的Saude段）相当的地层是一个有争议的问题，该序列被指定为密西西比纪至中侏罗世的年龄;时间跨度超过1.5亿年。利用现有的发表的数据和新的地球化学分析的Watrous组，我们提出了一个三叠纪的年龄下Watrous红层。已建立的测井对比将Saude段红层确定为中二叠世以后。一些先前发表的地球化学和孢粉学数据，从相当的地层是在这个年龄的协议，但一些古地磁研究提供了相互矛盾的结果，与密西西比到晚三叠世的年龄分配。我们的研究证明了Saude成员和下Watrous红层的等效性，通过扩展测井对比北部，从美国到萨斯喀彻温省。新的锶、硫和氧同位素分析结果表明，孤立的下沃特罗斯硬石膏结核的年龄与早三叠世或晚三叠世的年龄最为一致，这与前红层撞击构造的测井对比和钾氩测年结果一致。下沃特罗斯红层的宾夕法尼亚时代被认为是最不可能的。
Abstract The age of the Lower Watrous red-beds, which host hydrocarbon reserves in the Williston Basin, along with equivalent formations in Manitoba (Lower Amaranth Formation) and the U.S.A. (Saude Member of the Spearfish Formation) is a controversial subject, with this succession being assigned ages from Mississippian to Middle Jurassic; a timespan of over 150 million years. Using existing published data and new geochemical analyses on the Watrous Formation, we present a Triassic age for the Lower Watrous red-beds. An established well-log correlation dates the Saude Member red-beds as post- Middle Permian. Some previously published geochemical and palynological data from equivalent formations are in agreement with this age, but several palaeomagnetic studies have provided conflicting results, with age assignments of Mississippian through to Late Triassic. Our study demonstrates the equivalency of the Saude Member and Lower Watrous red-beds by extending the well-log correlation north, from the U.S.A. into Saskatchewan. The combined new strontium, sulfur and oxygen isotopic analyses of isolated Lower Watrous anhydrite nodules are most consistent with an Early or Late Triassic age, which is in agreement with the well-log correlation and potassium-argon dating of a pre-red-beds impact structure. A Pennsylvanian age for the Lower Watrous red-beds is considered most unlikely.