530 abstracts: ge;oi.ogy 



isons are also given between the deep-seated Appalachian brines, sea 

 water, and surface waters, intended to show the probable changes that 

 have taken place in the oil and gas field waters. In short, the com- 

 plete history of the waters is sketched, as nearly as it is possible to do 

 so, from the time of their inclusion in the sediments to the present. 

 Effects likely to be caused by changes in temperature and pressure 

 such as it is reasonable to suppose may have affected the strata are 

 pointed out. 



Some practical applications of the principles and discussion are 

 given. It is suggested that analyses of the waters in or near oil and 

 gas fields may throw light not only on the location of the more valu- 

 able fluids, but also on the probable reactions and precipitations that 

 might ensue when the different waters are allowed to mix either in the 

 wells or in the strata. Careful consideration should also be given to 

 the movements and rearrangements that the oil, gas, and water under- 

 go incident to extraction. R. C. W. 



GEOLOGY. — Relations of Late Paleozoic and Early Mesozoic forma- 

 tions of southwestern Montana and adjacent parts of Wyoming. 

 D. Dale Condit. U. S. Geol. Survey Prof. Paper 120-F. 19 18. 

 Pp. 111-121, pis. 5, fig. I. 



This paper presents evidence found in southwestern Montana con- 

 cerning the great Jurassic base-leveling and its bearing on the solution 

 of certain stratigraphic problems involving late Paleozoic, Triassic, 

 and Jurassic formations, and sets forth the relations of those formations 

 to beds in western Wyoming. The conclusions briefly summarized 

 are as follows: 



Prior to the encroachment of the sea from the northwest in late 

 Jurassic time prolonged erosion and base-leveling occurred over much 

 of the Rocky Mountain region. From Idaho State line near Yellow- 

 stone National Park northward to the vicinity of Helena the erosion 

 surface thus produced truncates beds of Triassic and Carboniferous 

 age, through a stratigraphic range of about 1,000 feet. 



The Quadrant quartzite at the type locality in the northwestern 

 part of Yellowstone Park is approximately equivalent to the Amsden 

 and Tensleep formations in Wyoming. The Park City (Pennsylvan- 

 ian and Permian), Dinwoody (Lower Triassic), and Chugwater (largely 

 Triassic) of the Wyoming section are in part represented by the Teton 

 formation of Yellowstone Park. The quartzitic cherty basal beds of 

 the Teton, containing the phosphate rock, are equivalent to the Phos- 



