GEOLOGY 143 



ture in the long fault scrap just east of Chaco Canyon. They 

 are in evidence, but not so clearly denned, elsewhere over 

 the region. Out crops of coal and Carbonaceous shale are 

 common in this locality but owing to the fact that there is 

 very little fracturing or faulting in this section, oil seepages 

 are practically unknown. 



The well which first brought Seven Lakes into prominence 

 as a possible oil district, is situated on the southeast quarter 

 of section 18, town 18 north, range 10 west. Oil and gas were 

 struck here in the latter part of June, 1911, by the Brock 

 Bros, while drilling for water. The well is 360 feet deep, size 

 of casing 6 inches. Water was struck at a depth of 58 feet 

 and rises within 27 feet of the surface. Through the kind- 

 ness of Mr. Brock a log of the lirst well is given below. 



Soft yellew material 22 feet 



Soft gray sandstone 38 feet 



Tough blue clay shale 40 feet 



Hard blue shale 20 feet 



Soft, sticky, blue, clay-shale. .40 feet 



Gray soft sandstone 20 feet 



Blue sticky shale fire clay. . . .60 feet 



Soft coal 6 feet 



Blue medium shale 34 feet 



White soft sand and shale .... 8 feet. Contains gas and oil. 



Blue gray medium shale 17 feet 



Brown hard sandstone 15 feet 



White soft shale and sand .... 20 feet. Contains gas and oil. 



Hard blue shale 20 feet 



The conditions here are not different from those of most 

 other oil regions. The oil sands of Pennsylvania run as low 

 as five feet in thickness while some of those of California run 

 as high as a hundred feet. x ln oil sands of different oil re- 

 gions the average is nearer that of the Seven Lakes region. 

 Some experts of the east regard 5 ft. of oil sands as paying 

 territory when other conditions are normal. It has been 

 estimated that in average conditions there may be from six 

 to twelve pints of oil in a cubic foot of sand but only three- 

 fourths of this is generally obtainable. While other esti- 

 mates place the average of 10 per cent porosity of the sands 



(1) Rles "Economic Geology." 



