|
|
|
|
|
| Swanner, Elizabeth D.; Planavsky, Noah J.; Lalonde, Stefan; Robbins, Leslie J.; Bekker, Andrey; Rouxel, Olivier; Saito, Mak A.; Kappler, Andreas; Mojzsis, Stephen J.; Konhauser, Kurt O.. |
| Cobalt (Co) is a bio-essential trace element and limiting nutrient in some regions of the modern oceans. It has been proposed that Co was more abundant in poorly ventilated Precambrian oceans based on the greater utilization of Co by anaerobic microbes relative to plants and animals. However, there are few empirical or theoretical constraints on the history of seawater Co concentrations. Herein, we present a survey of authigenic Co in marine sediments (iron formations, authigenic pyrite and bulk euxinic shales) with the goal of tracking changes in the marine Co reservoir throughout Earthʼs history. We further provide an overview of the modern marine Co cycle, which we use as a platform to evaluate how changes in the redox state of Earthʼs surface were... |
| Tipo: Text |
Palavras-chave: Cobalt; Trace element proxies; Ocean redox; Shale; Iron formation; Pyrite. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00174/28575/26986.pdf |
| |
|
|
| Nunes,Jaquelina A.; Schaefer,Carlos E.G.R.; Ferreira Júnior,Walnir G.; Neri,Andreza V.; Correa,Guilherme R.; Enright,Neal J.. |
| Vegetation and soil properties of an iron-rich canga (laterite) island on the largest outcrop of banded-iron formation in Serra de Carajás (eastern Amazonia, Brazil) were studied along a topographic gradient (738-762 m asl), and analyzed to test the hypothesis that soil chemical and physical attributes play a key role in the structure and floristic composition of these plant communities. Soil and vegetation were sampled in eight replicate plots within each of the four vegetation types. Surface (0-10 cm) soil samples from each plot were analyzed for basic cations, N, P and plant species density for all species was recorded. CCA ordination analysis showed a strong separation between forest and non-forest sites on the first axis, and between herbaceous and... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Amazon Forest; Canga; Carajás; Ferruginous campo rupestre; Iron formation; Laterite. |
| Ano: 2015 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652015000502097 |
| |
|
|
|
