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

德干地盾高精度 U-Pb 年龄模型

• 批准号: 1454430
• 负责人: Blair Schoene
• 金额: $ 8.91万
• 依托单位: Princeton University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-04-01 至 2017-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1454430&HistoricalAwards=false
• 关键词: precision; Pb; age; model; Deccan

A high-precision U-Pb age model for the Deccan Traps PI: Asst. Prof. Blair Schoene, Princeton Univ., [e-mail] 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.

德干圈闭的高精度U-Pb年龄模型国际和综合活动办公室/国际科学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工作，进行实地考察，并参与随后的样本分析，以尝试对德干圈闭进行高精度的喷发日期，并将这些日期与biostratigrpahy提供的独立时间轴进行比较。 白垩纪末的大灭绝是地球历史上最近的和公开可见的灾难，包括恐龙和其他大型动物的灭绝。尽管科学界普遍认为这次灭绝完全是由希克苏鲁布小行星撞击（墨西哥尤卡坦）造成的，但更多的证据表明，同期的大规模火山爆发可能对这场生态灾难起了重大作用。这些火山岩暴露在印度，被称为德干圈闭，由1.3立方公里的玄武岩组成。该建议的重点是提供高精度的德干圈闭喷发年龄，以便更好地将它们与独立的时间轴的灭绝和恢复跨越古近纪边界（KPB）。通过确定火山爆发的速度，通过德干地层，调查人员将估计火山气体排放量作为时间的函数。这些估计可以纳入晚白垩世气候变化模型，并与地球化学代用指标和化石记录进行比较，以更好地了解德干圈闭对KPB生物周转的潜在贡献。研究人员将采用化学研磨-同位素稀释-热电离质谱法（CA-ID-TIMS）与从德干玄武岩和玄武岩流之间的火山灰层中提取的锆石进行对比。他们的初步结果表明，这种方法是成功的，对流动沉积产生了± 2万至3万年的不确定性。这些初始数据包括对德干火山活动主要阶段的开始和结束的估计，并表明它将KPB与持续时间约75万年的KPB相结合;他们的新数据将包括整个3公里厚火山序列中爆发的高分辨率时间轴，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灭绝和希克苏鲁布影响的时间估计进行比较，并进一步与越来越多的生态和环境变化记录进行比较，这些记录都导致了主要的灭绝事件。由此产生的德干圈闭的年龄模型将是理解晚白垩世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。