abstracts: geology 37 



formation. This field continue^ to yield almost the entire production 

 of Texas until 1909, when the gas fields of Clay County were developed. 

 The Lower Cretaceous formations have not been reached in any of the 

 wells in the Corsicana field. 



The strata in the Corsicana field dip in general to the southeast at 

 a rate of 50 to 100 feet to the mile. The uniformity in direction and 

 amount of dip is interrupted at a number of places by folds, but none 

 of the folds are continuous over large areas. The greatest dips observed 

 on the folds are at the rate of 560 feet to the mile, and these high dips 

 are confined to small areas. The irregularities in the normal position 

 of the strata seems to have been produced by forces acting in two 

 directions, as two sj^stems of folds are determinable — one approxi- 

 matelj^ parallel to the dip of the rocks and the other at right angles to 

 it. So far as observed, there is no evidence of faulting, or breaking of 

 the rock strata, in this field. 



A review of the discussion of the structure or a study of the structure 

 map of the Corsicana field shows that oil and gas occur in this field 

 under two different structural conditions. They have accumulated 

 along the crests of well-defined anticlines, as in the Burke pool, and 

 also in beds of fairly uniform dip, as in the Corsicana pool. Drilling 

 has shown, however, that the sands of this field are lenticular and vary 

 in porosity and thickness from place to place. 



In the Corsicana district there are at least two productive sands 

 which are believed to belong to the Taylor formation — the Corsicana 

 and Edens sands. The Corsicana sand is the principal producing sand 

 and yields light oil and a small amount of gas at a number of places, 

 particularly toward the north end of the district. 



The oil of the Corsicana field is believed to have originated from 

 organic matter in the shales that inclose the sands and to a minor extent 

 in the sands themselves. R. W. Stone. 



GEOLOGY. — Structure of the northern part of the Bristow quadranylp, 



Creek County, Oklahoma, with reference to petroleum and natural 



gas. A. E. Fath. U. S. Geological Survey Bulletin 661-B. Pp. 



31, with maps, sections, and illustrations. 1917. 



The rocks exposed at the surface in the Bristow quadrangle and 



those beneath it to a depth of 2500 feet or more are a part of the Penn- 



sylvanian series, the series to which belong the surface rocks throughout 



the oil fields of northeastern Oklahoma. The strata dip slightly north 



of west about 50 feet to the mile, or a little more than half a degree. 



