THE KANSAS FIELDS 691 



the results of compression, as if lateral pressures to the westward accom- 

 panying the Ozark movement were opposed by pressures in the opposite 

 direction from the Eocky Mountains. The strata of the intervening ter- 

 ritory were here and there folded into anticlines, domes, terraces, and 

 monoclines with numerous sharp irregular waves or "noses'' along the 

 strike. These subordinate structures are the ones that control the posi- 

 tion of the oil and gas fields in southern Kansas and eastern Oklahoma. 



The local folding in Kansas was not regularly formed like the long 

 anticlines and synclines west of the Allegheny Mountains in Pennsylva- 

 nia and West Virginia, nor of those that border the Choctaw fault to the 

 southeast of the oil fields of Oklahoma. It is the rule in Kansas that oil 

 and gas occur on low folds separated from one another and showing a 

 tendency along the west limit of the fields to line up in a chain of related 

 bulges trending with the strike. Farther east in the State no definite 

 relationships can be worked out between neighboring structures, for they 

 occur without system and are distinct in type and form. Favorable con- 

 ditions for testing with the drill are often discovered in districts where 

 they are least expected. 



The strata of the Mississippian, Pennsylvanian, and Permian series 

 dip normally westward across Kansas at the average rate of about 30 feet 

 per mile. Across the oil fields the strike line is generally east of north 

 and west of south. Locally the strata are horizontal or dip to the east- 

 ward, reversing the normal dip. The total amount of the reverse dip in 

 feet constitutes the height of the structures, and varies from zero on the 

 terraces or noses to as much as 150 feet or more in the oil fields at Au- 

 gusta and Eldorado, or in the domes at Dexter and Elmdale, for examples 

 (see figure 2). 



OCCURRENCE OF GRANITE IN DOMES 



In connection with the structure of the Kansas fields, attention is 

 called to the occurrence of granite at reasonably shallow depths on some 

 of the local domes in that State. At Elmdale, Onaga, Wabaunsee, and 

 Zeandale granite is encountered at stratigraphic horizons as high as 1,000 

 feet above the base of the Pennsylvanian series. The fact that there is 

 no evidence of metamorphic action in the beds of shale and sandstone 

 immediately overlying these crystalline masses indicate that they are old 

 knobs which stood submerged in the Pennsylvanian sea. Deposition filled 

 aroimd them until they were ultimately covered, and at these points sub- 

 sequent compression developed lines of weakness, with consequent folding 

 of the strata above the knobs. The dome at Elmdale shows a reverse dip 

 of nearly 300 feet at angles as steep as 5 degrees. The depth from the 



