Collaborative Research: RUI: "CSI Devonian" - testing Late Devonian ocean anoxia proxies across different paleoenvironments

科学家如何确定物种大灭绝的原因？早在恐龙之前，生活在泥盆纪晚期(3.83-3.59亿年前)的海洋动物就受到了一系列灾难性事件的影响，包括地球历史上一些最严重和最广泛的死亡事件。与地球历史上所有其他重大物种灭绝不同的是，这一系列生物危机的原因仍然不清楚。大多数科学家认为，这些灭绝事件是由于海洋中氧气的损失，但在岩石记录中很难破译氧气损失的严重程度。我们通常用来识别海洋环境(痕迹化石、微化石、沉积物类型和化学特征)中的氧损失的工具是为那些既容易保存又容易识别的岩石类型开发的。但这些工具也适用于那些在岩石记录中不容易保存或识别氧气丢失的地方吗？该项目试图确定最常用的确定古代海洋氧气水平的方法是否适用于所有海洋环境，还是只适用于其中的一部分。通过这一过程，调查人员将制定一套全面的最佳做法来评估海洋沉积物中的氧损失(无论地质背景如何)，这反过来将有助于微调晚泥盆世灭绝脉冲的原因。该项目将涉及三所本科院校的教职员工和本科生研究人员，并将创建符合下一代科学标准的在线学习模块(主要是附带数据集和教师培训材料的视频)，用于6-12年级的面对面和远程学习。这种在线传播模式(称为“CSI：泥盆纪”)不仅扩大了该项目的地理覆盖范围，而且可以用于翻转课堂教学环境、家庭学校和远程学习阶段。372 Ma弗拉斯尼亚-法门期(F-F)和359 Ma泥盆纪-石炭纪(D-C)界线的晚泥盆世大灭绝事件是地球历史上最严重的大灭绝事件之一。尽管在Kellwasser事件和Hangenberg Black Shale事件中使用各种地球化学和痕量化石替代物对海洋缺氧进行了150项研究，但从古地理和古环境来看，晚泥盆世海洋缺氧仍然是一个谜和相当大的样本偏差，阻碍了这项工作。我们寻求资金，为跨越不同古环境和古地理位置的岩石形成一个内部一致的数据集，以便校准和验证最常用的海洋缺氧替代指标的实用性。我们建议开发一套全面的评估古海洋环境中氧损失的最佳实践，使用相同的缺氧替代方法(总有机碳、有机壁微化石、δ34SPY、δ34SCAS、δ13Ccarb、δ13Corg、微量元素地球化学、黄铁矿框体分布和遗迹组构)，以便在不同的古环境和沉积制度下评估替代效用。样本范围将包括基线缺氧前条件、缺氧条件和缺氧/消退后反弹条件。除了确定代理应用的最佳实践(无论时间段、缺氧事件或沉积环境)之外，我们得到的数据集将有助于重建晚泥盆世洋流、气候、构造、生态系统和物种灭绝。这项拟议的研究是由三所大学合作进行的，涉及多个国际和国内合作者，重点放在本科生培训和指导上。该提案还试图开发一个面向6-12年级学生的互动在线学习模块，该模块与下一代科学标准(NGSS)保持一致，重点关注科学家如何a)在现实生活中合作研究，b)使用经验证据对不同现象进行科学解释。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

How do scientists determine the cause of a mass extinction? Long before the dinosaurs, marine animals that lived during the Late Devonian time period (383-359 million years ago) were affected by a series of catastrophic events, including some of the most severe and widespread die-offs in Earth’s history. Unlike all of the other major mass extinctions in Earth's history, the reasons for this series of biological crises still remain unclear. Most scientists think that these extinction events were due to loss of oxygen from the oceans, but the severity of oxygen loss can be hard to decipher in the rock record. The tools we typically use to recognize oxygen loss in marine environments (trace fossils, microfossils, sediment type, and chemical signatures) were developed for rock types where oxygen loss is both easy to preserve and to recognize. But do these tools also work in places where oxygen loss is not as easy to preserve or recognize in the rock record? This project seeks to determine if the most commonly used methods for determining ancient ocean oxygen levels work across all marine environments, or only a subset of them. Through this process, the investigators will develop a comprehensive set of best practices for assessing oxygen loss in marine sediments (regardless of geologic setting), which in turn will help fine-tune the causes of the Late Devonian extinction pulses. This project will involve faculty and undergraduate researchers across three undergraduate institutions and will create online learning modules (primarily videos with accompanying data sets and teacher training materials) aligned with Next Generation Science Standards for both in-person and remote learning for grades 6-12. This online dissemination model (called “CSI: Devonian”) not only expands the geographic reach of this project, but can be used in flipped classroom teaching environments, homeschooling, and periods of remote learning. Late Devonian extinction events at the 372 Ma Frasnian-Famennian (F-F) boundary and 359 Ma Devonian-Carboniferous (D-C) boundary are some of the most severe mass extinctions in Earth's history. Despite 150 studies of ocean anoxia across the Kellwasser Events and Hangenberg Black Shale Event using a variety of geochemical and trace fossil proxies, Late Devonian ocean anoxia is still a mystery and considerable sample bias, both in terms of paleogeography and paleoenvironment, hinders this work. We seek funding to form an internally consistent dataset for rocks that span disparate paleoenvironments and paleogeographic locations, in order to both calibrate and validate the utility of the most commonly used ocean anoxia proxies. We propose to develop a comprehensive set of best practices for evaluating oxygen loss in ancient marine environments using the same anoxia proxy methodology (total organic carbon, organic walled microfossils, δ34SPY, δ34SCAS, δ13Ccarb, δ13Corg, trace element geochemistry, pyrite framboid distributions, and ichnofabrics) across a variety of sites and existing sample sets so that proxy utility can be assessed in different paleoenvironments and sedimentary regimes. The sample range will include baseline pre-anoxic conditions, anoxic conditions, and post-anoxic/extinction rebound conditions. In addition to determining the best practices for proxy application (regardless of time period, anoxic event, or depositional environment), our resulting dataset will help inform reconstructions of Late Devonian ocean currents, climate, tectonics, ecosystems, and extinctions. The proposed research is a cooperative effort by three universities involving multiple international and domestic collaborators and focuses heavily on undergraduate training and mentorship. The proposal also seeks to develop an interactive “CSI: Devonian” online learning module geared towards students in grades 6-12 that is aligned with the Next Generation Science Standards (NGSS), which focuses on how scientists a) collaborate on research in real life and b) use empirical evidence to derive scientific explanations of different phenomena.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.