nai

Project Progress

Rise of Oxygen

Work on this problem has reached its culmination, with a paper in press in Nature. In this paper we provide evidence in support of our hypothesis that a substantial increase in volcanism on land led to a reduction in total oxygen demand associated with oxidation of volcanic fluids (subaerial volcanic gases and submarine hydrothermal fluids) and thus the rise of atmospheric oxygen.

Modern Analogs for Anoxic Oceans

This year’s work focused on collection of samples and analytical method development to facilitate the identification of biomarkers associated with particular redox conditions along the gradient from oxygenated and high light to anoxic and dark. This work will come to fruition in the next several months.

Modeling Anoxic Oceans

Work continues on modifying an Earth system model of intermediate complexity, Genie, for use in the study of anoxic oceans in Earth history (e.g., the Proterozoic “Canfield” ocean and the Late Permian superanoxic ocean linked to mass extinction). We have now added a fully functional N cycle so that we can look at the possibility of a nutrient crisis during the transition from an anoxic to an oxic ocean (and vice versa) speculated upon by others.

Permian Mass Extinction

Three papers have been published on the Permian mass extinction, exploring disturbances to the C and S cycle through the event and into the Triassic. Suggestive links to Siberian Trap volcanism and subsequent development of highly sulfidic oceans have been found in the analysis of the C and S isotopic composition of Late Permian carbonates.

Effect of early life on soil development

We have been collecting profiles through ancient soils (paleosols) developed during the latest Precambrian and earliest Cambrian, the time of the explosion of metazoan life in the ocean, the end of the Snowball Earth episodes, and the time just before the establishment of eukaryotic terrestrial ecosystems. Core samples have been collected and analyzed from South Dakota and Iowa, and field samples have been collected and analyzed from Virginia and North Carolina. These have diagnostic indicators that they are paleosols, are intensely weathered, and have other indications that life flourished on land and affected soil development before the rise of vascular plants.