2 items with the tag “snowball earth

  • Life and Environments: Geochemistry of Late Precambrian Oxygenation
    NAI 2013 Massachusetts Institute of Technology Annual Report

    The first year of work marked a successful transition from the goals and projects defining our last NAI node and the initiation of new, exciting research lines. Recently, our work on the Ediacaran transition in the Earth system culminated in an integrated geochemical study that both covers the state of the late Precambrian world, but also serves as a critical tie point for our upcoming work on Cryogenian ocean and atmospheric chemistry. This entails the extension of similar tools to those we applied in the Ediacaran, as well as the development of a new 17O system in the Johnston Lab that will serve as a central measurement for the upcoming projects.

    ROADMAP OBJECTIVES: 4.1 4.2 5.2 6.1
  • Life and Environments: Proterozoic Geology, Geochemistry and Paleontology
    NAI 2013 Massachusetts Institute of Technology Annual Report

    The search for life on other planets, including Mars, is inevitably a comparative exercise with Earth as the only known planet that carries confirmed biosignatures (chemical or morphological). Often, these pursuits bridge multiple disciplines from sedimentology/stratigraphy, classic paleontology, inorganic and isotope geochemistry to the study and distribution of specific organic compounds that are considered good proxies for particular sorts of organisms (i.e. biomarkers). The Ediacaran Period (635 – 542 Ma) sees the first direct evidence for the rise of multicellularity, which is arguably one of the most critical biological transitions in the rock record. Equally intriguing is the immediately pre-ceding interval, the Cryogenian Period (850 – 635 Ma) with global glaciations, massive perturbations in geochemical cycles, a probable rise of atmospheric oxygen, and an apparent evolutionary radiation within the eukaryotic domain. In contrast to the canonical view, emerging research on Neoproterozoic sedimentary successions by the MIT-NAI team now suggests that much of the apparently sudden rise of animal life that is manifested in the Ediacaran sedimentary record was initiated by events that happened earlier, during the late Mesoproterozoic Era and through the Cryogenian Period (1200 – 650 Ma). Our work seeks to illuminate this time period by documenting the stratigraphy, isotopic records, fossil assemblages, and biomarker contents of critical Meso- to Neoproterozoic transitions in well-preserved Proterozoic sections from Canada and Russia. We especially seek to understand the genetic links and time relationships (which inform rates) among tectonic, geochemical and biological changes.