COLLABORATIVE RESEARCH: RUI: Testing hypotheses for Late Devonian biotic and climatic events via high-precision CA-TIMS U-Pb zircon dating and quantitative correlation tools

合作研究：通过高精度CA-TIMS U-Pb锆石定年和定量相关工具测试泥盆纪晚期生物和气候事件的假设摘要泥盆纪晚期发生了一系列全球性的生物灭绝事件，其规模之大，可以算作显生宙的大灭绝事件之一。然而，关于灭绝的成因机制以及海洋沉积、生物地球化学循环、海平面和气候的相关变化，尚未达成共识。验证泥盆纪晚期灭绝的相互竞争的假设？其中包括海平面波动和回归、气候变冷、海洋缺氧、流星撞击和/或大规模火山活动？目前由于缺乏足够的古生物学、构造学和代用气候记录的时间分辨率而受到阻碍。在这项研究中，一个由古生物学家、生物地层学家和同位素地球化学家组成的多学科研究团队将结合关键地层序列层间火山灰床的高精度U-Pb锆石地质年代学，以及应用于全球晚泥盆世多类群数据库的定量生物地层学，这些数据库是由文献和新的高分辨率采样编制的。U-Pb地质年代学将利用化学磨损和EARTHTIME四峰同位素稀释方法测量约0.1 Ma的分辨率年龄，这将通过约束优化校准晚泥盆世第一个高分辨率复合标准的构建。有了这个高分辨率的年龄模型，研究小组将探讨与泥盆纪晚期生物事件的突发性、它们的全球同步性和过程驱动因素有关的几个基本问题。需要解决的具体假设包括：地外撞击或大规模火山活动与生物危机之间的同步性和因果关系；相关的海平面上升和下降的速率以及碳循环和温度的代用记录的波动是否与milankovich波段轨道强迫相一致；以及气候、冰川期、海洋缺氧和碳循环之间的反馈是否导致了晚泥盆纪生物危机。本研究将通过本科生参与多学科国际科学团队来影响STEM人力资源开发；发展国际科学合作；支持地球时代地质年代学倡议的科学使命及其相关的接触和推广计划；为许多其他古生代气候研究提供了从根本上改进的年表；并提高我们对深层气候状态转变的理解，这种转变可能类似于导致我们目前冰窖的那些变化。拟议研究的科学过程和内容将由nsf资助的并行STEM教育计划捕获，该计划开发了一系列基于网络的学习对象，用于教授地质年代学和地球历史科学。

COLLABORATIVE RESEARCH: Testing hypotheses for Late Devonian biotic and climatic events via high-precision CA-TIMS U-Pb zircon dating and quantitative correlation toolsMark Schmitz, EAR-1124488Boise State UniversityD. Jeffrey Over, EAR-1124275SUNY GeneseoABSTRACT The Late Devonian period hosts a series of global biological extinction events of such magnitude as to be counted among the major mass extinctions of the Phanerozoic. Yet no consensus has yet been reached regarding the causative mechanisms of extinction and associated changes in marine sedimentation, biogeochemical cycling, sea level and climate. Testing of competing hypotheses for Late Devonian extinctions?which include sea-level fluctuations and regression, climatic cooling, ocean anoxia, bolide impact, and/or massive volcanism?is currently hampered by a lack of sufficient temporal resolution in paleobiological, tectonic and proxy climate records.In this study, a multi-disciplinary research team of paleontologists, biostratigraphers and isotope geochemists will combine high-precision U-Pb zircon geochronology on interstratified volcanic ash beds in key stratigraphic successions with quantitative biostratigraphy applied to a global Late Devonian multi-taxa database compiled from the literature and new high-resolution sampling. The U-Pb geochronology will utilize the chemical abrasion and EARTHTIME quadruple spike isotope dilution methods to measure ca 0.1 Ma resolution ages, which will calibrate the construction of the first highly resolved composite standard for the Late Devonian via constrained optimization. With this high resolution age model the research team will interrogate several fundamental questions relating to the abruptness of the late Devonian biotic events, their global synchrony, and process drivers. Specific hypotheses to be addressed include the synchrony and causality between extraterrestrial impacts or massive volcanism and biotic crises, whether the rates of associated eustatic rise and fall and fluctuations in proxy records of carbon cycling and temperature are consistent with Milankovich-band orbital forcing, and if feedbacks between climate, glacioeustasy, ocean anoxia, and the carbon cycle caused the Late Devonian biotic crises.This research will impact STEM human resource development via participation of undergraduate students in a multi-disciplinary international science team; develop international scientific collaborations; support the science mission of the EARTHTIME geochronology initiative, and its associated inreach and outreach programs; provide fundamentally improved chronologies for numerous other Paleozoic climate studies; and improve our understanding of deep time climate state transitions potentially analogous to those leading to our current icehouse. The scientific process and content of the proposed research will be captured by a parallel NSF-funded STEM education initiative developing a series of web-based learning objects to teach the science of geochronology and Earth history.