190 proceedings: geological society 



fornia, discloses the following facts, (a) Some of the deepest waters are 

 as salty as sea water, while in others chlorides are practically lacking. 

 The distribution of the chlorides is apparently a function of the freedom 

 of the underground circulation, which is controlled largely by geologic 

 structure, (b) Sulphates, which are the predominating salts in the 

 normal ground water on the west side of the San Joaquin Valley, 

 diminish rather regularly in amount as the oil zone is approached and 

 finally disappear, but outside of the oil fields their quantity remains 

 constant to great depths or even increases, (c) Carbonates increase 

 as the oil zone is approached, and if no chlorides are present constitute 

 the only dissolved salts in the waters associated with the oil. 



These marked variations in the character of the waters are presum- 

 ably due to reaction between them and the hydrocarbons, by which 

 the sulphate is reduced to H 2 S and the hydrocarbons oxidized to car- 

 bonate and C0 2 . Carbon dioxide, doubtless derived in this way, is 

 present in the hydrocarbon gas in these fields and usually occurs in 

 greatest quantity (up to 35 per cent) nearest the outcrop, where the 

 sulphate waters enter the strata and where the reaction would be most 

 vigorous. It is probable also that part of the H 2 S formed is oxidized 

 to sulphur, which would react with the oil and make it heavier and 

 more asphaltic. In general, the heaviest oil is that nearest the outcrop 

 and that in the zone of "tar sands" above the main oil zone, where the 

 sulphate water would exercise its greatest effect. The occurrence of the 

 heavier oil nearest the surface has hitherto been ascribed to oxidation, 

 but the action of sulphur derived from the sulphate waters is believed 

 to have been more important. 



The 303d meeting was held in the lecture room of the Cosmos Club 

 on January 26, 1916. 



REGULAR PROGRAM 



G. F. Loughlin: Faulting in the Tintic Mining District, Utah. Five 

 periods of faulting are recognized: (a) faulting during the later stages 

 of the period of folding; (b) faulting during the subsequent period of 

 recoil; (c) faulting due to igneous intrusions, especially that of the 

 main monzonite stock; (d) Assuring and faulting just after igneous 

 intrusion, providing channels for the ore-forming solutions; (e) post- 

 mineral Assuring and faulting. The largest faults in the mining district 

 proper are included in groups (a) and (c). They had only minor 

 influence in determining the locations of ore bodies. 



A detailed discussion of the faulting will be included in a forth- 

 coming report of the United States Geological Survey on the geology 

 and ore deposits of the Tintic District. 



Philip S. Smith: Notes on the geology of the Lake Clark-Iditarod 

 region, Alaska. The speaker described the areal geology of the Lake 

 Clark-Iditarod region, Alaska. This region is located in southwestern 

 Alaska, extending from the Pacific Mountains to the central part of 

 the Yukon Plateau province. The rocks are dominantly sedimentary 



