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Biomarker Evidence for Photosynthesis During Neoproterozoic Glaciation

Author:
Olcott, Alison N., Sessions, Alex L., Corsetti, Frank A., Kaufman, Alan J., Oliviera, Tolentino Flavio de
Source:
Science 2005 v.310 no.5747 pp. 471-474
ISSN:
0036-8075
Subject:
biomarkers, carbon, eukaryotic cells, euphotic zone, glaciation, ice, latitude, microbial ecology, photosynthesis, photosynthetic bacteria, primary productivity, rocks, surface water, Brazil
Abstract:
Laterally extensive black shales were deposited on the São Francisco craton in southeastern Brazil during low-latitude Neoproterozoic glaciation [approximately]740 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.
Agid:
1530833