Sulfur isotope variations in marine sulfate evaporites and the phanerozoic oxygen budget

On the basis of the sulfur isotope age curve of marine sulfate evaporites and currently available numerical data for the sulfur cycle the stationary terrestrial sulfate reservoir has been calculated as a function of time for the last 600×106 yr, this also giving information on the partial inventory of photosynthetic oxygen locked up in sedimentary and marine SO42−. The results obtained confirm previous concepts (arrived at by geochemical flux models) of a sizable interchange of material between both sedimentary sulfur reservoirs and, accordingly, varying amounts of oxygen stored as sedimentary sulfate (this amount fluctuating between some 0.5 and 1.5×1022 g during the Phanerozoic). With the constancy of the sedimentary δ13Ccarb record indicating that the crustal Corg reservoir and its stoichiometric oxygen equivalent (i.e., total photosynthetic oxygen) did not change very much during the last quarter of the earth's history, fluctuations in sulfate oxygen must have been buffered by the two other O2 inventories, namely, oxygen fixed as Fe(III) oxide and free oxygen of the atmosphere. Although the main responsibility for balancing variations in sedimentary sulfate would go to the fixed oxygen because of its overwhelming size, repercussions on the free oxygen can by no means be excluded. If we accept a variation of free oxygen proportionate to that of the sum of the two reservoirs as a minimum requirement, then atmospheric PO2 can be expected to have fluctuated during the Phanerozoic within some ±20% of its present level.

[1]  M. Schidlowski,et al.  Model calculations for the terrestrial carbon cycle: carbon isotope geochemistry and evolution of photosynthetic oxygen , 1975 .

[2]  M. Schidlowski,et al.  Isotopic fractionation between coexisting organic carbon—carbonate pairs in Precambrian sediments , 1975 .

[3]  M. Schidlowski,et al.  Precambrian sedimentary carbonates: carbon and oxygen isotope geochemistry and implications for the terrestrial oxygen budget☆ , 1975 .

[4]  JAMES C. G. Walker,et al.  Stability of atmospheric oxygen , 1974 .

[5]  H. D. Holland,et al.  Systematics of the isotopic composition of sulfur in the oceans during the Phanerozoic and its implications for atmospheric oxygen , 1973 .

[6]  M. Schidlowski.  Sulfur in the precambrian metallogeny , 1973 .

[7]  H. Schwarcz,et al.  Influence of sedimentary environments on sulfur isotope ratios in clastic rocks: a review , 1973 .

[8]  P. Deines,et al.  The isotopic composition of carbonatite and kimberlite carbonates and their bearing on the isotopic composition of deep-seated carbon , 1973 .

[9]  H. D. Holland,et al.  The geologic history of sea water—an attempt to solve the problem , 1972 .

[10]  Yuan-hui Li.  Geochemical mass balance among lithosphere, hydrosphere, and atmosphere , 1972 .

[11]  W. Broecker.  A boundary condition on the evolution of atmospheric oxygen , 1970 .

[12]  A. Schneider.  The sulfur isotope composition of basaltic rocks , 1970 .

[13]  R. Garrels,et al.  Sedimentary Rock Types: Relative Proportions as a Function of Geological Time , 1969, Science.

[14]  John A. S. Adams,et al.  Computer-derived geochemical balances and element abundances , 1966 .

[15]  H. Nielsen.  Schwefelisotope im marinen Kreislauf und das δ34 S der früheren Meere , 1966 .

[16]  M. L. Keith,et al.  Carbon and oxygen isotopic composition of selected limestones and fossils , 1964 .

[17]  W. H. Gross,et al.  Sulfur isotope abundances in basic sills, differentiated granites, and meteorites , 1963 .

[18]  J. Smith,et al.  The distribution and isotopic composition of sulfur in coal , 1974 .

[19]  R. Garrels,et al.  Chemical History of the Oceans Deduced from Post Depositional Changes in Sedimentary Rocks , 1974 .

[20]  H. Holland.  Marine Evaporites and the Composition of Sea Water During the Phanerozoic , 1974 .

[21]  M. Rutten.  The origin of life by natural causes , 1971 .

[22]  C. Rees.  The sulphur isotope balance of the ocean: an improved model , 1970 .

[23]  E. Degens.  Biogeochemistry of Stable Carbon Isotopes , 1969 .

[24]  A. B. Ronov.  PROBABLE CHANGES IN THE COMPOSITION OF SEA WATER DURING THE COURSE OF GEOLOGICAL TIME1 , 1968 .

[25]  L. C. Marshall,et al.  The Rise of Oxygen in The Earth's Atmosphere with Notes on the Martian Atmosphere*† , 1967 .

[26]  W. T. Holser,et al.  Isotope geochemistry of sedimentary sulfates , 1966 .