Co-evolution of Earth and life across the Proterozoic-Phanerozoic transition

PIs Emmy Smith (John Hopkins University), David Evans (Yale University), Brenhin Keller (Dartmouth College), Kimberley Lau (Penn State University), Alan Rooney (Yale University), Justin Strauss (Dartmouth College), Shuhai Xiao (Virginia Tech) and additional team members.

Project description

The Ediacaran–Cambrian transition (ECT; ca. 580–530 Ma) represents one of the most profound geobiological events in Earth history, marking the sudden appearance and subsequent proliferation of all major animal groups in the fossil record. This time interval also records significant environmental and geochemical perturbations to the Earth system, such as evidence for global marine anoxia, rapid continental motions, and unprecedented fluctuations in Earth’s biogeochemical cycles. A number of hypotheses have been proposed to link these interactions among Earth’s sedimentary, hydrological, tectonic, geodynamic, and biotic systems; however, the temporal record of these changes is currently underdeveloped, and the interrelationships among these different systems require integration of disparate datasets from a wide spectrum of disciplines. We have assembled a diverse team of researchers that range from field geologists to geoinformaticists to geophysicists, not only to generate the most precise and accurate Ediacaran–early Cambrian timescale ever achieved, but also to test fundamental hypotheses regarding the Earth system at the dawn of animal life.

By generating a much-needed temporal framework for the ECT, we can interrogate and further develop hypotheses related to the co-evolution of life and environment across the most iconic boundary in the geologic record. Here, we propose to generate collaborative field- and lab-based activities to integrate sedimentological, geochemical, paleontological, geochronological, and paleomagnetic records from six key Ediacaran–Cambrian sedimentary successions worldwide. Our project will also provide support to the International Continental Drilling Program (ICDP)-funded “Geological Research through Integrated Neoproterozoic Drilling: The Ediacaran–Cambrian Transition” (GRIND-ECT) project, which represents a one-time, community-wide effort for Earth scientists to obtain unique Ediacaran–early Cambrian core material. The extensive, continuous sampling throughout the Ediacaran and lower Cambrian provided by drill core in the GRIND-ECT project, coupled with our proposed field campaigns and modeling components, provides an opportunity to advance Ediacaran–Cambrian chronology and set the stage for a new generation of research opportunities and questions.

Through this new collaboration, we aim to provide new insights into the following outstanding questions about the ECT:

  • What is the timing and tempo of the diversification and extinction of Ediacaran organisms?
  • What was the pattern of oxygenation, at both global and regional scales, during the ECT?
  • What was the timing, duration, and nature the Shuram and basal Cambrian carbon isotope excursions (CIEs), and can these isotopic shifts be used to reliably construct age models across the ECT?
  • What global paleogeographic changes happened across the ECT, and how might they have perturbed global geochemical cycles and the biosphere?

Our proposal is a timely effort that we expect will not only answer testable hypotheses, but also produce an integrated dataset that will in itself generate new hypotheses and help guide a community-wide effort to understand the nature and drivers of this major geobiological transition. To address these gaps, we propose the following goal: develop an integrated and temporally-calibrated record of the sedimentological, geochemical, paleontological, paleogeographic, and geodynamic conditions across the Proterozoic-Phanerozoic transition (580–530 Ma). To achieve this broad goal, we divide our proposed research into three Themes with associated hypotheses that we view encompass some of the most fundamental unanswered questions in the Ediacaran–Cambrian Earth system:

Theme 1: Temporal calibration of Ediacaran–Cambrian Earth-life changes

Theme 2: Documenting and modeling geochemical change in the context of metazoan evolution

Theme 3: Ediacaran–Cambrian paleogeography with implications for life and environment