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

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.