442 abstracts: geology 



in the Simi region at the present time on account of its association 

 with the Simi oil field. 



As the object of this paper is to make recommendations bearing on 

 both developed and possible new territory in the Simi Valley, the con- 

 ditions under which the oil occurs in the field situated on the flanks 

 of the Santa Susana Mountains and Oak Ridge are briefly reviewed. 

 The more productive wells according to the records appear to be 

 either along the axis of the anticline or immediately north of it. 



R. W. Stone. 



GKOIyOGY. — Anticlines in a part of the Musselshell Valley. C. F. 

 BowEN. U.S.Geol. Survey Bull. 691- F. pp. 185-209, pi. I. 1918. 



Previous investigations had shown that the Musselshell Valley, 

 Montana, is an area in which the rocks have undergone considerable 

 folding. The work has demonstrated the existence within the area studied 

 of several well-developed anticlines and domes, which seem to offer 

 structurally favorable places for the accumulation of oil and gas. The 

 demonstration of the presence or absence of commercial accumulations 

 of these fluids in the folds has been less conclusive, owing largely to the 

 imdeveloped condition of the area. 



. Sandstones that would serve as suitable reservoirs for the accumula- 

 tion of oil occur at several horizons, (i) Near the top of the Colorado 

 shale there is a transition zone of thin sandstones and sandy shale 

 beds. (2) About 1200 feet below the top of the Colorado. (3) About 

 250 to 300 feet lower in the section is another sandstone of similar 

 character, but much thinner and more distinctly conglomeratic. 

 (4) Associated with and underlying the Mowry shale member, 

 in the eastern part of the field, are several thin, finely conglomeratic 

 sandstones. (5) At the top of the Kootenai there is 40 to 50 

 feet of platy, rather fine grained sandstone in approximately the same 

 position as the Greybull sand of the Big Horn Basin, Wyoming. 

 (6) Near the base of the Kootenai there is another coarse, porous 

 sandstone of undetermined thickness. 



The Eagle sandstone is not a likely source of oil or gas in most of 

 this area, for it has been removed from the crests of most of the anti- 

 clines, and thus any oil or gas that may have originally been stored in 

 it has had an opportunity to escape. 



This report discusses the geology of the region as a whole, and also 

 suggests the most favorable places for future development. 



R. W. Stone. 



