Biomarker Evidence for Photosynthesis During

• Main Authors: Neoproterozoic Glaciation, Alison N. Olcott, Alex L. Sessions, Frank A. Corsetti, Alan J. Kaufman, Tolentino Flavio De Oliviera
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Sea ice
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.490.9778; http://www.geol.umd.edu/~kaufman/pdf/Olcott_05.pdf

Laterally extensive black shales were deposited on the São Francisco craton in southeastern Brazil during low-latitude Neoproterozoic glaciation È740 to 700 million years ago. These rocks contain up to 3.0 weight % organic carbon, which we interpret as representing the preserved record of abundant marine primary productivity from glacial times. Extractable biomarkers reflect a complex and productive microbial ecosystem, including both phototrophic bacteria and eukaryotes, living in a stratified ocean with thin or absent sea ice, oxic surface waters, and euxinic conditions within the photic zone. Such an environment provides important constraints for parts of the ‘‘Snowball Earth’ ’ hypothesis. The impacts of low-latitude Neoproterozoic glaciation on the biosphere are widely debated (1–6). On one hand, one conception of BSnowball Earth [ envisions sea-ice cover thick enough to preclude photosynthesis over most of