@article {718,
	title = {The evolution of the Earth surface sulfur reservoir},
	journal = {American Journal of Science},
	volume = {304},
	year = {2004},
	note = {889sqTimes Cited:142Cited References Count:59},
	month = {Dec},
	pages = {839-861},
	abstract = {The surface sulfur reservoir is in intimate contact with the mantle. Over long time scales, exchange with the mantle has influenced the surface reservoir size and possibly its isotopic composition. Processes delivering sulfur to the Earth surface from the mantle include volcanic outgassing, hydrothermal input, and ocean crust weathering. The sulfide fixed in ocean crust as a consequence of hydrothermal sulfate reduction, and subduction of sedimentary sulfides, represent return pathways of sulfur to the mantle. The importance of these different pathways in influencing the size of the surface sulfur reservoir depends on the particulars of ocean and atmosphere chemistry. During times of banded iron formation when the oceans contained dissolved iron, sulfide from submarine hydrothermal activity was precipitated on the seafloor and subsequently subducted back into the mantle and, therefore, had little impact on the surface sulfur reservoir size. With sulfidic ocean bottom water conditions, which may have occurred through long stretches of the Mesoproterozoic and Neoproterozoic, significant amounts of sulfide is subducted into the mantle. When the oceans are oxic, sulfide subduction is unimportant, and an additional source, ocean crust weathering, delivers sulfur to the Earth surface. Thus, under oxic conditions the surface environment accumulates sulfur, and probably has for most of the last 700 million years.Mass balance modeling suggests that the surface sulfur reservoir may have peaked in size in the early Mesoproterozoic, declined to a minimum in the Neoproterozoic, and increased to its present size through the Phanerozoic. The exchange of sulfur between the mantle and the surface environment can also influence the isotopic composition of the surface reservoir. Modeling shows that the subduction of S-34- depleted sulfur through the Mesoproterzoic could have significantly increased the average delta(34)S of the surface reservoir into the late Neoproterozoic. The preserved isotope record through the Neoproterozoic is well out of balance, with the average delta(34)S for sulfate and sulfide both exceeding the modem crustal average. This imbalance could be explained, at least partly, if the crustal average was more S-34-enriched than at present, as the modeling presented here suggests.},
	issn = {0002-9599},
	doi = {10.2475/ajs.304.10.839},
	author = {Canfield, D. E.}
}
@article {251,
	title = {New insights into the burial history of organic carbon on the early Earth},
	journal = {Geochemistry Geophysics Geosystems},
	volume = {5},
	year = {2004},
	note = {id: 1506; 846RU Times Cited:14 Cited References Count:44},
	pages = {1-9},
	abstract = {[1] The isotope record of organic matter and calcium carbonate is often used to infer the burial history of organic carbon through time. As organic carbon burial is widely held to control long-term oxygen production, the isotope record also relates to the production rates of oxygen on Earth. Current interpretations of the record suggest a long-term consistency in the proportion of total carbon buried as organic carbon (f ratio), with some important periods of much higher burial proportions. The isotope record is analyzed here with a new carbon isotope mass balance model, which considers submarine hydrothermal weathering of ocean crust as a significant removal pathway of inorganic carbon. With this model the f ratio is considerably reduced if isotopically depleted inorganic carbon is precipitated during hydrothermal weathering and if hydrothermal weathering dominates inorganic carbon removal from the surface environment. In contrast to previous calculations, our analysis of the carbon isotope record shows that organic carbon burial in the Archean accounted for only between 0\% and 10\% of the total carbon burial. These low burial proportions would have contributed to a slow accumulation of atmospheric oxygen in the Archean.},
	issn = {1525-2027},
	doi = {10.1029/2004gc000713},
	author = {Bjerrum, C. J. and Canfield, D. E.}
}
@article {763,
	title = {A new model for Proterozoic ocean chemistry},
	journal = {Nature},
	volume = {396},
	year = {1998},
	note = {145klTimes Cited:530Cited References Count:29},
	month = {Dec 3},
	pages = {450-453},
	abstract = {There was a significant oxidation of the Earth{\textquoteright}s surface around 2 billion years ago (2 Gyr)(1-4). Direct evidence for this oxidation comes, mostly, from geological records of the redox-sensitive elements Fe and U reflecting the conditions prevailing during weathering(1-3). The oxidation event was probably driven by an increased input of oxygen to the atmosphere arising from an increased sedimentary burial of organic matter between 2.3 and 2.0 Gyr(5). This episode was postdated by the final large precipitation of banded iron formations around 1.8 Gyr(1,2). It is generally believed that banded iron formations precipitated from an ocean whose bottom waters contained significant concentrations of dissolved ferrous iron, and that this sedimentation process terminated when aerobic bottom waters developed, oxidizing the iron and thus removing it from solution(1,2). In contrast, I argue here that anoxic bottom waters probably persisted until well after the deposition of banded iron formations ceased; I also propose that sulphide, rather than oxygen, was responsible for removing iron from deep ocean water. The sulphur-isotope record supports this hypothesis as it indicates increasing concentrations of oceanic sulphate, starting around 2.3 Gyr(6), leading to increasing rates of sulphide production by sulphate reduction. The increase in sulphide production became sufficient, around 1.8 Gyr,to precipitate the total flux of iron into the oceans. I suggest that aerobic deep-ocean waters did not develop until the Neoproterozoic era (1.0 to similar to 0.54 Gyr), in association with a second large oxidation of the Earth{\textquoteright}s surface. This new model is consistent with the emerging view of Precambrian sulphur geochemistry and the chemical events leading to the evolution of animals, and it is fully testable by detailed geochemical analyses of preserved deep-water marine sediments.},
	issn = {0028-0836},
	doi = {10.1038/24839},
	author = {Canfield, D. E.}
}
