Solving a tuff problem: Defining a chronostratigraphic framework for Middle to Upper Jurassic nonmarine strata in eastern Australia using uranium–lead chemical abrasion–thermal ionization mass spectrometry zircon dates
Solving a tuff problem: Defining a chronostratigraphic framework for Middle to Upper Jurassic nonmarine strata in eastern Australia using uranium–lead chemical abrasion–thermal ionization mass spectrometry zircon dates
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解决凝灰岩问题：利用铀-铅化学磨损-热电离质谱锆石测年法确定澳大利亚东部中上侏罗统非海相地层的年代地层框架
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发表时间：
2018
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通讯作者：
J. Crowley
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作者：
C. Wainman;P. McCabe;J. Crowley
为了更好地预测储层结构和河流控制地层中未发现资源的位置，需要一个合理的年代地层框架。本研究重新评估了澳大利亚东部Eromanga、苏拉特和Clarence-Moreton盆地含油气侏罗纪河湖序列的地层格架。地层对比是具有挑战性的，因为异岩相，缺乏传统的地层标志层，和孢粉地层带的寿命。横向不连续的火山气降凝灰岩和火山砂岩横跨澳大利亚东部的侏罗纪的丰度允许建设一个新的，区域年代地层框架。对3个盆地13口威尔斯井的31个样品进行了高精度锆石U-Pb化学研磨-热电离质谱（CA-TIMS）年龄测定，年龄范围为168.07 ± 0.07 ~ 149.08 ± 0.06 Ma。五年代地层基准面的定义和外推到677个威尔斯井的时间间隔为420 ka或更少的数百公里的澳大利亚东部。新的年代地层框架揭示了不准确的岩石地层单位的基础上挑选岩性和有线测井特征，并显示含煤相的瓦隆煤炭措施是两个情节的煤（泥炭）积累分离的不整合。该研究还表明，通过激光烧蚀-电感耦合等离子体质谱分析后的U-Pb CA-TIMS测年火山砂岩中最年轻的锆石，将年代地层基准扩展到邻近盆地的凝灰岩床的可行性。这些数据对澳大利亚东部的中、上侏罗纪地层进行了重大修订。精确的U-Pb CA-TIMS测年有助于阐明其他盆地非海相层序的岩相结构，并有助于石油开发。
To better predict the architecture of reservoirs and the location of undiscovered resources in fluvial-dominated strata, a sound chronostratigraphic framework is needed. This study reassesses the stratigraphic framework of petroleum-bearing Jurassic fluviolacustrine successions in the Eromanga, Surat, and Clarence–Moreton Basins of eastern Australia. Correlation of the strata is challenging because of the heterolithic facies, the absence of conventional stratigraphic marker beds, and the longevity of palynostratigraphic zones. The abundance of laterally discontinuous volcanic air–fall tuffs and volcanogenic sandstones across the Jurassic of eastern Australia allows for the construction of a new, regional chronostratigraphic framework. High-precision U-Pb zircon chemical abrasion–thermal ionization mass spectrometry (CA-TIMS) dates ranging from 168.07 ± 0.07 Ma to 149.08 ± 0.06 Ma were obtained from 31 samples from 13 wells across 3 basins. Five chronostratigraphic datums were defined and extrapolated to 677 wells within a time interval of 420 ka or less over hundreds of kilometers across eastern Australia. The new chronostratigraphic framework reveals inaccuracies in picking lithostratigraphic units based on lithology and wire-line log characteristics and shows coal-bearing facies of the Walloon Coal Measures to be two episodes of coal (peat) accumulation separated by an unconformity. The study also demonstrates the feasibility of extending chronostratigraphic datums to neighboring basins without tuff beds by dating the youngest zircon in volcanogenic sandstones by U-Pb CA-TIMS following laser ablation–inductively coupled plasma mass spectrometry analysis. The dates provide a substantial revision to the Middle to Upper Jurassic stratigraphy of eastern Australia. The use of precise U-Pb CA-TIMS dates should help elucidate the lithofacies architecture of nonmarine successions in other basins and assist in petroleum development.