A high-precision U-Pb age model for the Deccan Traps

Deccan Traps PI的高精度U-Pb年龄模型：普林斯顿大学Blair Schoene助理教授，bschoene@Princeton.EDUThe国际和综合活动/国际科学办公室与沉积地质学和古生物学共同资助了该提案。摘要本提案的重点是与前往印度的美国教师和学生进行国际合作，与他们的印度合作者一起进行实地考察，并参与随后的样本分析，以尝试德干圈闭的高精度喷发日期，并将这些日期与生物地层学提供的独立时间线进行比较。~66 Ma白垩纪末期大灭绝是地球历史上最近的、公开可见的灾难，包括恐龙和其他大型动物的灭绝。尽管科学界普遍认为灭绝完全是由希克苏鲁伯小行星撞击造成的（Yucatán，墨西哥），但更多的证据表明，同期的大型火山爆发可能对这场生态灾难起了重要作用。这些火山岩暴露在印度，被称为德干圈闭，由1.3平方公里的玄武岩组成。这一建议的重点是提供德干圈闭的高精度喷发年龄，以便更好地将它们与白垩纪-古近纪边界（KPB）的灭绝和恢复的独立时间线进行比较。通过测定德干地层学中火山喷发的速率，研究人员将估算火山气体释放量随时间的函数。这些估计可以纳入晚白垩世气候变化模型，并与地球化学代理和化石记录进行比较，以更好地了解德干圈闭对KPB生物转换的潜在贡献。为了实现这些目标，研究人员将使用化学磨损-同位素稀释-热电离质谱法（CA-ID-TIMS）对从德干玄武岩和玄武岩流之间的火山灰烬床中提取的锆石进行分析。他们的初步结果表明，这种方法是成功的，产生了±2 -3万年的流动沉积的不确定性。这些初步资料包括德干火山活动主要阶段的开始和结束的估计，并表明它与持续时间约750 kyr的KPB相吻合；他们的新数据将包括整个3公里厚的火山序列的高分辨率喷发时间表，这对于评估挥发性物质随时间的释放至关重要。这些日期可以与最近公布的KPB灭绝和希克苏鲁伯撞击时间的估计进行比较，并进一步与导致主要灭绝事件前后日益增强的生态和环境变化记录进行比较。由此得出的德干圈闭年龄模型将成为理解晚白垩纪生态变化和随后重建地球生物圈的整体方法的重要组成部分。

A high-precision U-Pb age model for the Deccan Traps PI: Asst. Prof. Blair Schoene, Princeton Univ., bschoene@Princeton.EDUThe Office of International and Integrative Activities/International Science co-funded the proposal with Sedimentary Geology and Paleobiology. ABSTRACTThis proposal focuses on an international collaboration with U.S. faculty and students travelling to India to work with their Indian collaborators, conduct fieldwork, and engage in subsequent analysis of samples to attempt high-precision eruption dates for the Deccan Traps and compare those dates with the independent timeline provided by biostratigrpahy. The ~66 Ma end-Cretaceous mass extinction is the most recent and publicly visible catastrophe in Earth history, encompassing the demise of dinosaurs and other large animals. Despite widespread scientific consensus that the extinction was caused solely by the Chicxulub asteroid impact (Yucatán, Mexico), additional evidence suggests that large, contemporaneous volcanic eruptions may have contributed significantly to this ecological disaster. These volcanic rocks are exposed in India and known as the Deccan Traps and comprise 1.3 km3 of basalt. This proposal focuses on providing high-precision eruption ages for the Deccan Traps in order to better compare them with the independent timeline of extinction and recovery across the Cretaceous-Paleogene boundary (KPB). By determining rates of volcanic eruptions through the Deccan stratigraphy, the investigators will estimate the volume of volcanic gasses emitted as a function of time. These estimates can be incorporated into models of late-Cretaceous climate change and compared with geochemical proxy and fossil records to better understand the potential contribution of the Deccan Traps to biologic turnover at the KPB.To achieve these goals, the investigators will apply chemical abrasion-isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS) to zircons extracted from within the Deccan basalts and from volcanic ashbeds between basalt flows. Their initial results show this approach to be successful, producing uncertainties on flow deposition to ±20-30 thousand years. These initial data include estimates of the onset and termination of the main phase of Deccan volcanism and show it to bracket the KPB with a duration of ~750 kyr; their new data will include a high-resolution timeline for the eruptions throughout the entire 3 km thick volcanic sequence, which is critical for assessing volatile release through time. These dates can be compared to recently published estimates for the timing of the KPB extinction and Chicxulub impact, and further compared to increasingly bolstered records of ecological and environmental change both leading up to and following the main extinction event. The resulting age model for the Deccan Traps will be an essential component of a holistic approach towards understanding late-Cretaceous ecological change and the subsequent rebuilding of Earth's biosphere.