Fluctuations in depositional conditions during the onset of severe climate events in Earth history predispose stratigraphic archives to hiatuses, often hindering complete reconstructions of paleoclimate events and their triggers. Several studies have proposed that a hiatus of unknown duration exists at the base of Oceanic Anoxic Event 2 (OAE2) in the North American Western Interior Basin at the base Turonian global boundary stratotype section and point (GSSP) in Pueblo, Colorado, which potentially influences integrated radioisotopic, biostratigraphic, and astrochronologic age models of the Cenomanian-Turonian boundary interval. To quantify the duration of this hiatus, refine the chronology of OAE2, and assess marine geochemical perturbations associated with the onset of the event, we present new 40Ar/39Ar dates from regional bentonites along with a new proximal-distal chemostratigraphic transect of the epeiric Western Interior Basin (WIB), including initial osmium isotope (Osi) and stable carbon isotope (δ13C) data. The new 40Ar/39Ar age determinations confirm and further constrain previous estimates of Cenomanian-Turonian boundary timing. Further, the regional chemostratigraphic synthesis demonstrates the conformity of the OAE2 successions correlated to Pueblo, shows that the duration of the lag between the onset of the Osi and δ13C excursions is ∼60 k.y., and thus constrains the magnitude of the pre-OAE2 hiatus in Pueblo to less than this value. The new astronomically tuned, conformable Osi record across the onset of OAE2 captures a geologically rapid onset of large igneous province volcanism, consistent with other records, such that the addition of CO2 to the ocean-atmosphere system may have driven changes in marine carbonate chemistry. Additionally, the refined chronostratigraphy of OAE2 and the Cenomanian-Turonian boundary in the central WIB improves correlation with other records, such as those in the Eagle Ford Group, Texas. The correlations highlight that discrepancies among OAE2 age models from globally distributed sections commonly stem from differing definitions of the event and uncertainties associated with astronomical tuning, in addition to stratigraphic preservation.

中文翻译：

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西部内陆盆地（美国），西诺曼尼亚-突尼斯海洋缺氧事件2（OAE2）区间的区域年代地层合成：新的Re-Os化学地层学和40Ar / 39Ar地球年代学

在地球历史上发生严重的气候事件期间，沉积条件的波动使地层档案易于发生裂隙，常常阻碍了对古气候事件及其触发因素的全面重建。多项研究表明，在北美西部内陆盆地大洋性缺氧事件2（OAE2）的底部，科罗拉多州普韦布洛的Turonian全球边界平流层剖面和点（GSSP）的底部存在一个未知持续时间的裂隙。塞诺曼尼亚-土伦边界区间的综合放射性同位素，生物地层学和天文年龄年龄模型。为了量化此中断的持续时间，请完善OAE2的时间顺序，并评估与事件发生相关的海洋地球化学扰动，我们介绍了来自区域膨润土的新40Ar / 39Ar日期，以及新的西部西部内陆盆地（WIB）的近端-远侧化学地层学断面，包括初始同位素（Osi）和稳定碳同位素（δ13C）数据。新的40Ar / 39Ar年龄确定证实并进一步限制了先前的Cenomanian-Turonian边界时间估计。此外，区域化学地层学合成证明了与Pueblo相关的OAE2演替的一致性，表明Osi发生与δ13C漂移之间的滞后时间约为60 ky，因此限制了OAE2之前裂隙的强度。镇值要小于此值。在OAE2爆发期间，新的经天文调整的Osi记录记录了大火成岩省火山活动在地质上的迅速爆发，与其他记录一致，例如向海洋-大气系统中添加二氧化碳可能推动了海洋碳酸盐化学的变化。此外，OAE2的精细年代地层和WIB中央的Cenomanian-Turonian边界改善了与其他记录的相关性，例如德克萨斯州Eagle Ford组的记录。相关性突出表明，OAE2年龄模型与全球分布区域之间的差异通常源于事件的不同定义以及与天文学调整相关的不确定性以及地层保留。OAE2的精细年代地层和WIB中央的Cenomanian-Turonian边界改善了与其他记录的相关性，例如德克萨斯州Eagle Ford组的记录。相关性突出表明，OAE2年龄模型与全球分布区域之间的差异通常源于事件的不同定义以及与天文学调整相关的不确定性以及地层保留。OAE2的精细年代地层和WIB中央的Cenomanian-Turonian边界改善了与其他记录的相关性，例如德克萨斯州Eagle Ford组的记录。相关性突出表明，OAE2年龄模型与全球分布区域之间的差异通常源于事件的不同定义以及与天文学调整相关的不确定性以及地层保留。