No abstract

Protection against arsenic damage in organisms positioned deep in the tree of life points to early evolutionary sensitization. Here, marine sedimentary records reveal a Proterozoic arsenic concentration patterned to glacial-interglacial ages. The low glacial and high interglacial sedimentary arsenic concentrations, suggest deteriorating habitable marine conditions may have coincided with atmospheric oxygen decline after ~2.1 billion years ago. A similar intensification of near continental margin sedimentary arsenic levels after the Cryogenian glaciations is also associated with amplified continental weathering. However, interpreted atmospheric oxygen increase at this time, suggests that the marine biosphere had widely adapted to the reorganization of global marine elemental cycles by glaciations. Such a glacially induced biogeochemical bridge would have produced physiologically robust communities that enabled increased oxygenation of the ocean-atmosphere system and the radiation of the complex Ediacaran-Cambrian life.

PostprintThis is the accepted version of a paper published in GFF. This paper has been peer-reviewed but does not include the final publisher proof-corrections or journal pagination.Citation for the original published paper (version of record):Arvestål, E., Streng, M. (2013) Cyrtograptids from the Telychian (upper Llandovery) of Kinnekulle Mountain, southern lapworthi indicates that the most proximal cladium was not necessarily the first to be formed.It appears that the first cladium originated distally and more proximal cladia formed afterwards as a counterbalance to the growing rhabdosome, allowing the organism to remain stable in the water column.