98 
OIL-FIELD WATERS IN SAN JOAQUIN VALLEY, CAL. 
sentation of the type of change that takes place, the intermediate 
stages in the decomposition of the hydrocarbons on the one hand 
and of the sulphate on the other being as yet unknown. 
Just as sulphate by reduction yields sulphide, so sulphide under 
other conditions may oxidize to sulphate. Whether alkaline sul¬ 
phide is the first product of reduction or not, the final product is 
hydrogen sulphide, and this gas is readily oxidized to produce free 
sulphur, probably in accordance with the equation 
2H 2 S + 0 2 = 2H 2 0 4- 2S 
Thus, free sulphur has been found in a number of marine muds, 
where it is doubtless formed by the oxidation of hydrogen sulphide 
derived from the sulphate in the sea water. 1 Under more strongly 
oxidizing conditions, or in the presence of certain bacteria, the sulphur 
becomes thiosulphate, sulphite, and finally sulphate. The com¬ 
plete reversion of hydrogen sulphide to sulphate is probably not 
widespread in deeply buried strata, but the change to free sulphur, 
which may take place even on the floor of the ocean, must be taken 
into account. It may also be noted that the oxidation of hydrogen 
sulphide to sulphur or sulphate results in the evolution of much 
heat, 2 3 * and if the earth temperatures in oil regions are higher than 
elsewhere, as suggested by Koenigsberger and Muhlberg, 8 some of 
the excess may be contributed by this reaction. 
FORMATION OF CARBONATE. 
In the few published accounts of oil-field waters special stress is 
laid on the absence of sulphate as discussed in the preceding section, 
but no attempt has been made, so far as the writer can learn, to work 
out the relations of the various types of water or to explain the sig¬ 
nificance of the carbonate. If the reduction of the sulphate is to be 
ascribed to the action of hydrocarbons, however, the formation of 
carbonate is a necessary concomitant, and the presence of unusual 
amounts of carbonate in oil-field waters may be explained by this 
reaction. 
The proportion of carbonate formed during the reduction of a 
definite amount of sulphate is not known and can not be determined 
until the stages involved in the reaction have been critically studied. 
Murray and Irvine report that the increase in the alkalinity of sea 
water associated with bottom muds is proportional to its loss in sul- 
1 Buchanan, J. Y., On the occurrence of sulphur in marine muds and nodules, and its bearing on their 
mode of formation: Roy. Soc. Edinburgh Proc., vol. 18, p. 17, 1890-91; Clarke, F. W., The data of geo¬ 
chemistry, 3d ed.: U. S. Geol. Survey Bull. 616, p. 514,1916. 
2 Becker, G. F., Geology of the quicksilver deposits of the Pacific slope: U. S. Geol. Survey Mon. 13, 
p. 254,1888. 
3 Koenigsberger, J.,and Muhlberg, M., Uber Messungen der geothermischen Tiefenstufe: Neues Jahrb., 
Beilage Band 31, pp. 107-157, 1911. 
