Stratigraphic constraints on early animal evolution

The base of the Cambrian is an eon-scale stratigraphic boundary that marks a major transition in global biodiversity with the subsequent radiation of modern animal phyla. Despite proliferation of a wide range of mechanistic hypotheses regarding relationships among environmental, evolutionary, and ecological change across the Ediacaran–Cambrian boundary, the scarcity of radioisotope geochronologic data for this interval consistently surfaces as an obstacle in rigorously testing these theories. This has led to enduring controversy on whether the Cambrian radiation is better understood through a Darwinian “gradualist” lens or a Gouldian “catastrophic” lens. In this talk, I will present integrated stratigraphic data sets from southern Africa and southwestern North America, including paleontology, stable isotope geochemistry, and high-precision U-Pb geochronology data. I compare these broadly coeval, Ediacaran–Cambrian marine sedimentary records to constrain rates of environmental and evolutionary change during this critical phase in the origination of the modern biosphere.

About this Series: The Department Lecture Series at EAPS at MIT is a series of weekly talks given by leading thinkers in the areas of geology, geophysics, geobiology, geochemistry, atmospheric science, oceanography, climatology, and planetary science. For more information and Zoom password please contact Madelyn Musick: mmusick@mit.edu