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.

德干地盾的高精度 U-Pb 年龄模型 PI：助理教授 Blair Schoene，普林斯顿大学，[e-mail] 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 该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，并参与随后对样本进行分析，尝试确定德干地盾的高精度喷发日期，并将这些日期与生物地层学提供的独立时间表进行比较。约 66 Ma 的白垩纪末大规模灭绝是地球历史上最近的、公开可见的灾难。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（墨西哥尤卡坦半岛）造成的，但更多证据表明，大型的、同时期的动物灭绝。这些火山岩暴露在印度，被称为德干地盾，由 1.3 平方公里的玄武岩组成，该提案的重点是提供德干地盾的高精度喷发年龄，以便更好地进行比较。通过德干地层确定火山喷发的速率，研究人员将在白垩纪-古近纪边界（KPB）上对它们进行独立的灭绝和恢复时间表。估计随时间变化的火山气体排放量。这些估计值可以纳入白垩纪晚期气候变化模型中，并与地球化学代理和化石记录进行比较，以更好地了解德干地盾对 KPB 生物周转的潜在贡献。为了实现这些目标，研究人员将对从德干玄武岩和从他们的初步结果表明这种方法是成功的，对流沉积产生了±20-3万年的不确定性。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。将 KPB 的持续时间定为约 750 kyr；他们的新数据将包括整个 3 公里厚的火山序列中喷发的高分辨率时间表，这对于评估随时间变化的挥发物释放至关重要。这些日期可以与最近发布的对 KPB 灭绝和希克苏鲁伯影响的时间估计进行比较，并进一步与主要灭绝事件之前和之后的生态和环境变化记录进行比较，从而得出德干灭绝事件的年龄模型。陷阱将成为了解白垩纪晚期生态变化和随后地球生物圈重建的整体方法的重要组成部分。