Biomarker Evidence for Photosynthesis During
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...
| Main Authors: | , , , , , |
|---|---|
| Other Authors: | |
| Format: | Text |
| Language: | English |
| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.496.9446 http://www.gps.caltech.edu/~als/library/research_articles/2005/olcott2005.pdf |
| Summary: | 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 |
|---|