title: Biomarker evidence for photosynthesis during neoproterozoic glaciation.
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.
authors.affiliation: Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, USA. olcott@usc.edu
authors.forename: Alison N
authors.initials: AN
authors.lastname: Olcott
authors.forename: Alex L
authors.initials: AL
authors.lastname: Sessions
authors.forename: Frank A
authors.initials: FA
authors.lastname: Corsetti
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Kaufman
authors.forename: Tolentino Flavio
authors.initials: TF
authors.lastname: de Oliviera
mesh_terms: D018407:Bacterial Physiological Phenomena; D015415:Biomarkers / Q000032:analysis; D001938:Brazil; D002244:Carbon / Q000032:analysis*; D002247:Carbon Isotopes / Q000032:analysis; D002254:Carbonates / Q000032:analysis; D000458:Cyanobacteria / Q000502:physiology; D017753:Ecosystem; D019015:Geologic Sediments / Q000737:chemistry*; D046448:Ice Cover; D009930:Organic Chemicals / Q000032:analysis*; D010788:Photosynthesis; D012623:Seawater / Q000382:microbiology*; D013472:Sunlight
chemical_list: D015415:Biomarkers; D002247:Carbon Isotopes; D002254:Carbonates; D009930:Organic Chemicals; D002244:Carbon