Paleobiology Seminar


Monday, March 6, 2017, 3:00pm


Haller Hall (Geological Museum)
Andrew Czaja
Assistant Professor, Department of Geology
University of Cincinnati
“Sulphur oxidation, biodiversity, and oxygenation in the Archean”

Czaja Talk Image

Abstract: The first 2 billion years of Earth’s history was an important time for life when microbes evolved and diversified into essentially all of the metabolic forms that now exist. Because of feedbacks between biology and the surface environment, understanding Earth’s biological history can help us understand the evolution of Earth itself. The morphological and geochemical evidence for this ancient biological history is sparse but is increasing. In this talk I will discuss new evidence for 2.52 Ga exceptionally large (20 to 265 µm), organic, smooth-walled, coccoidal microfossils preserved in a deep-water black chert from the Kaapvaal craton of South Africa. Morphologically these fossils are similar to Proterozoic and Phanerozoic acritarchs and to some Archean fossils interpreted as possible cyanobacteria. Comparison with modern taxa, however, suggest they were sulfur-oxidizing bacteria similar to those of the modern genus Thiomargarita, organisms that live in anoxic and sulfuric deepwater settings. These are the oldest reported fossil sulfur oxidizing bacteria and reveal a diversity of life and ecosystems, previously only interpreted from geochemical proxies, just prior to the Great Oxidation Event, a time of major atmospheric evolution. [Background Reading and Supplemental info]

The Geobiology/Paleobiology Seminar Series is jointly hosted by OEB and EPS