Refined geochronology and revised stratigraphic nomenclature of the Upper Cretaceous Wahweap Formation, Utah, USA and the age of early Campanian vertebrates from southern Laramidia
Refined geochronology and revised stratigraphic nomenclature of the Upper Cretaceous Wahweap Formation, Utah, USA and the age of early Campanian vertebrates from southern Laramidia
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DOI：
10.1016/j.palaeo.2022.110876
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发表时间：
2022-02-25
影响因子：
3
通讯作者：
Sertich, Joseph J. W.
中科院分区：
文献类型：
--
作者：
Beveridge, Tegan L.;Roberts, Eric M.;Sertich, Joseph J. W.
北美西部内陆保存了世界上最完整的上白垩纪海相和非海相地层序列之一;其中，犹他州南部凯帕洛维茨高原的森诺曼-坎帕尼亚单位是陆地环境和生物群的重要档案。在这里，我们提出了新的放射性同位素年龄坎帕尼亚Wahweap组，沿着岩石地层修订，以改善其化石生物群的地质背景。Kaiparowits高原上广泛接受的Wahweap组的非正式地层细分在此正式化，并命名为Last Chance Creek Member、Reynolds Point Member、Coyote Point Member和Parabel峡谷Member（以前分别为下部、中部、上部和盖层砂岩段）。利用CA-ID-TIMS获得了两个高精度的榴辉岩锆石U-Pb年龄，并得到了5个膨润土和碎屑锆石LA-ICP-MS年龄的支持。通过CA-ID-TIMS对雷诺兹点段底部的星星渗漏膨润土进行的改进地质年代学研究表明，这一重要的标志层位比以前认为的要早100多万年。使用新的地质年代学数据构建了Wahweap组的贝叶斯年龄地层模型，产生了统计上稳健的年龄和相关的不确定性，这些不确定性可量化地解释沉积物累积速率的潜在变化。新的年代地层格架将上、下组界线分别定为82.17 ± 1.47/-10.63Ma和77.29 ± 0.72/-0.62Ma，从而将其时代限定为Campanian期的前半期。此外，对Wahweap组中已知的脊椎动物化石地点进行了全面审查，以更好地了解它们的时空分布，包括对标志性恐龙谱系的早期成员（如暴龙科，鸭嘴龙科和Centrosaurinae）的年龄进行了修订。Wahweap组及其组成生物组合的年代和岩石地层细化为解决坎帕尼亚陆地古生态学和宏观进化问题，包括整个北美西部的恐龙特有性和多样性，建立了一个重要的参考。
The Western Interior of North America preserves one of the most complete successions of Upper Cretaceous marine and non-marine strata in the world; among these, the Cenomanian-Campanian units of the Kaiparowits Plateau in southern Utah are a critical archive of terrestrial environments and biotas. Here we present new radioisotopic ages for the Campanian Wahweap Formation, along with lithostratigraphic revision, to improve the geological context of its fossil biota. The widely accepted informal stratigraphic subdivisions of the Wahweap Formation on the Kaiparowits Plateau are herein formalized and named the Last Chance Creek Member, Reynolds Point Member, Coyote Point Member, and Pardner Canyon Member (formerly the lower, middle, upper, and capping sandstone members respectively). Two high-precision U-Pb zircon ages were obtained from bentonites using CA-ID-TIMS, supported by five additional bentonite and detrital zircon LA-ICP-MS ages. Improved geochronology of the Star Seep bentonite from the base of the Reynolds Point Member via CA-ID-TIMS demonstrates that this important marker horizon is over a million years older than previously thought. A Bayesian age-stratigraphic model was constructed for the Wahweap Formation using the new geochronologic data, yielding statistically robust ages and associated uncertainties that quantifiably account for potential variations in sediment accumulation rate. The new chronostratigraphic framework places the lower and upper formation boundaries at 82.17 +1.47/-10.63 Ma and 77.29 +0.72/-0.62 Ma, respectively, thus constraining its age to the first half of the Campanian. Additionally, a holistic review of known vertebrate fossil localities from the Wahweap Formation was conducted to better understand their spatio-temporal distribution including revised ages for early members of iconic dinosaur lineages such as Tyrannosauridae, Hadrosauridae, and Centrosaurinae. Chronoand lithostratigraphic refinement of the Wahweap Formation and its constituent biotic assemblages establishes an important reference for addressing questions of Campanian terrestrial paleoecology and macroevolution, including dinosaur endemism and diversification throughout western North America.