ii 4 c - H - GORDON 



of the beds is very irregular. The sandstones, shales, and clays 

 grade into each other both vertically and horizontally. Moreover 

 there is a monotonous similarity in the sandstones and shales 

 respectively throughout the area, which, taken in connection with 

 the absence of any persistent easily recognizable stratum, renders 

 the stratigraphic correlation of the beds, except within very narrow 

 limits, practically impossible. 



In eastern Clay and Montague counties, the beds, considered 

 Cisco, show a greater development of sandstones some of which 

 are conglomeratic. In the western part of the area, however, no 

 true conglomerates were observed. 



As to the thickness of the Wichita, no definite statement can 

 be made. Certain of the beds may be traced for a limited distance 

 sufficient to indicate a general westward dipping of the strata. 

 Cummins estimates it to be 35 feet per mile, which is probably 

 too high. The width of the outcrop in an east-west direction is 

 about 50 miles, which, assuming a regular inclination of 25 feet 

 per mile, would give a thickness of 1,250 feet for the beds out- 

 cropping in this portion of the field. How much of this should be 

 referred to the Cisco is conjectural, but probably not less than 

 half. A well put down for oil at Electra, which is located near the 

 top of the formation, passes through 1,790 feet of red clays with 

 some sandstone and red sandy shales. At Petrolia, which is near 

 the middle of the outcrop, the oil wells are for the most part about 

 400 feet deep, chiefly in red clays and shales. Drilling has extended 

 to a depth of 800 feet in some instances and indicates an increase 

 in the proportion of blue shales below, but no reliable record could 

 be obtained of the lower formations passed through. 



At Archer City a well 737 feet deep shows red clays and reddish 

 sandstones predominating to a depth of 670 feet. Below this the 

 drill revealed similar deposits but in diminished proportion, as 

 compared with the light-colored sands and bluish clays. Since 

 the upper beds of the Cisco in this region are prevailingly red, how- 

 ever, no reliable conclusion can be drawn from well records as to the 

 plane of division between the formations. 



In the bluffs of the Wichita River in the northwestern corner 

 of Archer County some beds of limestones aggregating 4 feet in 



